Showing 1–50 of 168 results for author: Kozlov, G

Demonstrating CBM Capabilities by $Λ$ Baryon Reconstruction in Ni+Ni Collisions with the mCBM Experiment at SIS18 of GSI/FAIR

Authors: CBM Collaboration, A. Agarwal, Z. Ahammed, N. Ahmad, L. J. Ahrens, M. Al-Turany, N. Alam, J. An, J. Andary, A. Andronic, H. Appelshäuser, B. Arnoldi-Meadows, B. Artur, M. D. Azmi, M. Balzer, A. Bandyopadhyay, V. A. Bâsceanu, J. Becker, A. Belousov, A. Bercuci, R. Berendes, D. Bertini, O. Bertini, M. Beyer, O. Bezshyyko , et al. (318 additional authors not shown)

Abstract: The Compressed Baryonic Matter (CBM) experiment at the upcoming Facility for Antiproton and Ion Research (FAIR) is a high-rate fixed-target experiment designed to investigate nuclear matter at extreme baryon densities in relativistic nucleus-nucleus collisions. To enable high-statistics measurements of rare probes, CBM is designed to operate at event rates up to 10 MHz. This necessitates the devel… ▽ More The Compressed Baryonic Matter (CBM) experiment at the upcoming Facility for Antiproton and Ion Research (FAIR) is a high-rate fixed-target experiment designed to investigate nuclear matter at extreme baryon densities in relativistic nucleus-nucleus collisions. To enable high-statistics measurements of rare probes, CBM is designed to operate at event rates up to 10 MHz. This necessitates the development of fast and radiation-tolerant detectors, self-triggered front-end electronics, a free-streaming data acquisition architecture, and real-time event reconstruction capabilities. Prototype versions and pre-series productions of the CBM detector systems have been deployed in the mini-CBM demonstrator setup mCBM - an experimental precursor comprising sub-components of all major CBM systems, installed at the SIS18 facility of GSI/FAIR within the FAIR Phase-0 program. In 2024, Ni+Ni collisions at a kinetic beam energy of 1.93 AGeV and an average interaction rate of about 250 kHz were successfully recorded. This dataset enables a detailed evaluation of the operational performance of the detector systems as well as the complete CBM data chain, while the reconstruction of rare $Λ$ baryons serves as a natural benchmark. This paper presents the first results on $Λ$ signal reconstruction with the mCBM experiment, demonstrating the readiness of the detector technologies and the data chain for the upcoming full-scale CBM experiment. △ Less

Submitted 1 June, 2026; originally announced June 2026.

Axion-Exchange Contribution to the Energy of Lithium-Like Ions

Authors: R. R. Abdullin, A. V. Volotka, D. A. Glazov, M. G. Kozlov, A. D. Moshkin, D. V. Chubukov

Abstract: Axions and axion-like particles are among the most promising candidates for dark matter and for manifestations of new physics beyond the Standard Model. In the present work, the contribution of axion exchange to the energy of lithium-like ions is investigated within the framework of relativistic bound-state quantum electrodynamics. A formalism for the interelectronic interaction mediated by axion… ▽ More Axions and axion-like particles are among the most promising candidates for dark matter and for manifestations of new physics beyond the Standard Model. In the present work, the contribution of axion exchange to the energy of lithium-like ions is investigated within the framework of relativistic bound-state quantum electrodynamics. A formalism for the interelectronic interaction mediated by axion exchange is developed in the Furry picture with finite nuclear size taken into account. Energy shifts are calculated for a wide range of nuclear charge numbers \(Z\) and axion masses. The magnitude of the axion-induced contribution is shown to increase with increasing \(Z\) for all states considered. Based on the analysis of lithium-like bismuth, constraints on the axion-electron interaction parameters are obtained in the high-mass region. The results indicate that precision spectroscopy of highly charged ions is a promising tool for searches for new physics associated with the exchange of pseudoscalar bosons. △ Less

Submitted 12 May, 2026; originally announced May 2026.

High partial waves contribution in calculations of the polyvalent atoms

Authors: M. G. Kozlov

Abstract: High accuracy calculations of atomic properties require using long basis sets. In particular, it is necessary to include large number of partial waves and estimate truncation corrections. The convergence in partial waves is known to be rather slow, so calculations become very costly. We use valence perturbation theory [PRA \textbf{105}, 052805 (2022)] to calculate contribution of the high partial… ▽ More High accuracy calculations of atomic properties require using long basis sets. In particular, it is necessary to include large number of partial waves and estimate truncation corrections. The convergence in partial waves is known to be rather slow, so calculations become very costly. We use valence perturbation theory [PRA \textbf{105}, 052805 (2022)] to calculate contribution of the high partial waves and estimate truncation corrections. These estimates may be useful to make assessment of theoretical error in atomic calculations more reliable. △ Less

Submitted 25 March, 2026; v1 submitted 12 March, 2026; originally announced March 2026.

Comments: 5 pages, 2 figures; v2: 2 references added and discussion extended

Testing Exotic Electron-Electron Interactions with the Helium Ionization-Energy Anomaly

Authors: Lei Cong, Filip Ficek, Rinat Abdullin, Mikhail G. Kozlov, Dmitry Budker

Abstract: Precision atomic spectroscopy provides a sensitive probe of physics beyond the Standard Model. A recently reported $9σ$ theory-experiment discrepancy in the ionization energy of metastable helium has motivated the hypothesis of a new boson mediating exotic electron-electron interactions. Using a model-independent sign-consistency analysis of the induced energy shifts, we show that the sign require… ▽ More Precision atomic spectroscopy provides a sensitive probe of physics beyond the Standard Model. A recently reported $9σ$ theory-experiment discrepancy in the ionization energy of metastable helium has motivated the hypothesis of a new boson mediating exotic electron-electron interactions. Using a model-independent sign-consistency analysis of the induced energy shifts, we show that the sign requirement alone excludes vector-vector and pseudoscalar-pseudoscalar interactions as possible explanations of the anomaly. Incorporating existing constraints together with improved limits obtained here further excludes axial-vector scenarios. Within the single-boson framework considered in this work, only a narrowly constrained scalar-mediated interaction remains viable. The remaining parameter space could be probed, for example, by modest improvements in the determination of the electron gyromagnetic ratio. △ Less

Submitted 10 February, 2026; originally announced February 2026.

Comments: 5 pages, 3 figures

Acetaldehyde as a molecule for testing variations of electron-to-proton mass ratio

Authors: J. S. Vorotyntseva, S. A. Levshakov, M. G. Kozlov

Abstract: We present the quantum-mechanical calculations of the dimensionless sensitivity coefficients Q to small changes in the fundamental physical constant mu = m_e/m_p - the electron-to-proton mass ratio - for a number of low-frequency (1-50 GHz) transitions of the acetaldehyde (CH3CHO) molecule. The calculations show that Q varies in the range from 0.62 to 3.61. An example of the practical use of the C… ▽ More We present the quantum-mechanical calculations of the dimensionless sensitivity coefficients Q to small changes in the fundamental physical constant mu = m_e/m_p - the electron-to-proton mass ratio - for a number of low-frequency (1-50 GHz) transitions of the acetaldehyde (CH3CHO) molecule. The calculations show that Q varies in the range from 0.62 to 3.61. An example of the practical use of the CH3CHO and CH3OH lines tracing the same regions in three molecular clouds, located at large galactocentric distances (D_GC ~ 8 kpc) is considered. This results in a limit on the mu variations of Delta mu/mu = (0.1 +/- 0.4)*10^(-7) which is in line with previously obtained most stringent upper limits on changes in mu based on other molecules and methods. The limit obtained restricts hypothetical violations of the Einstein principle of the local position invariance at the level of 4*10^(-8) in the Galactic disk at large galactocentric distances. △ Less

Submitted 24 December, 2025; originally announced December 2025.

Comments: 9 pages, 7 tables, 1 figure. Accepted for publication in Phys. Rev. A

The High Level Trigger and Express Data Production at STAR

Authors: Wayne Betts, Jinhui Chen, Yuri Fisyak, Hongwei Ke, Ivan Kisel, Pavel Kisel, Grigory Kozlov, Jeffery Landgraf, Jerome Lauret, Tonko Ljubicic, Yugang Ma, Spyridon Margetis, Hao Qiu, Diyu Shen, Qiye Shou, Xiangming Sun, Aihong Tang, Gene Van Buren, Iouri Vassiliev, Baoshan Xi, Zhenyu Ye, Zhengqiao Zhang, Maksym Zyzak

Abstract: To meet the demands of the Beam Energy Scan phase-II (BES-II) program, the STAR experiment at RHIC developed a dual real-time framework consisting of a High Level Trigger (HLT) and an Express Data Production system (xProduction). The HLT operates online within the Data Acquisition (DAQ) chain on a multicore CPU cluster, with optional acceleration using Xeon Phi coprocessors. It employs paralleli… ▽ More To meet the demands of the Beam Energy Scan phase-II (BES-II) program, the STAR experiment at RHIC developed a dual real-time framework consisting of a High Level Trigger (HLT) and an Express Data Production system (xProduction). The HLT operates online within the Data Acquisition (DAQ) chain on a multicore CPU cluster, with optional acceleration using Xeon Phi coprocessors. It employs parallelized algorithms, such as the Cellular Automaton track finder, for fast tracking, vertexing, and event filtering, enabling real-time event selection and detector monitoring. In parallel, xProduction runs independently of the DAQ loop and performs near offline-quality calibration and reconstruction within hours. Using the express data stream, enhanced by HLT selections, and the STAR calibration framework, it enables early physics analysis and provides collaboration-wide access to analysis-ready datasets. Together, HLT and xProduction form a complementary system combining real-time selection with rapid high-quality reconstruction. This framework has enabled prompt reconstruction of the ${}^5_Λ\mathrm{He}$ hypernucleus and efficient processing of large datasets, demonstrating scalability for future high-luminosity experiments. △ Less

Submitted 25 March, 2026; v1 submitted 5 August, 2025; originally announced August 2025.

Comments: 14 figures, 2 tables

Journal ref: NIMA Volume 1088, August 2026, 171489

Future Circular Collider Feasibility Study Report: Volume 2, Accelerators, Technical Infrastructure and Safety

Authors: M. Benedikt, F. Zimmermann, B. Auchmann, W. Bartmann, J. P. Burnet, C. Carli, A. Chancé, P. Craievich, M. Giovannozzi, C. Grojean, J. Gutleber, K. Hanke, A. Henriques, P. Janot, C. Lourenço, M. Mangano, T. Otto, J. Poole, S. Rajagopalan, T. Raubenheimer, E. Todesco, L. Ulrici, T. Watson, G. Wilkinson, A. Abada , et al. (1439 additional authors not shown)

Abstract: In response to the 2020 Update of the European Strategy for Particle Physics, the Future Circular Collider (FCC) Feasibility Study was launched as an international collaboration hosted by CERN. This report describes the FCC integrated programme, which consists of two stages: an electron-positron collider (FCC-ee) in the first phase, serving as a high-luminosity Higgs, top, and electroweak factory;… ▽ More In response to the 2020 Update of the European Strategy for Particle Physics, the Future Circular Collider (FCC) Feasibility Study was launched as an international collaboration hosted by CERN. This report describes the FCC integrated programme, which consists of two stages: an electron-positron collider (FCC-ee) in the first phase, serving as a high-luminosity Higgs, top, and electroweak factory; followed by a proton-proton collider (FCC-hh) at the energy frontier in the second phase. FCC-ee is designed to operate at four key centre-of-mass energies: the Z pole, the WW production threshold, the ZH production peak, and the top/anti-top production threshold - delivering the highest possible luminosities to four experiments. Over 15 years of operation, FCC-ee will produce more than 6 trillion Z bosons, 200 million WW pairs, nearly 3 million Higgs bosons, and 2 million top anti-top pairs. Precise energy calibration at the Z pole and WW threshold will be achieved through frequent resonant depolarisation of pilot bunches. The sequence of operation modes remains flexible. FCC-hh will operate at a centre-of-mass energy of approximately 85 TeV - nearly an order of magnitude higher than the LHC - and is designed to deliver 5 to 10 times the integrated luminosity of the HL-LHC. Its mass reach for direct discovery extends to several tens of TeV. In addition to proton-proton collisions, FCC-hh is capable of supporting ion-ion, ion-proton, and lepton-hadron collision modes. This second volume of the Feasibility Study Report presents the complete design of the FCC-ee collider, its operation and staging strategy, the full-energy booster and injector complex, required accelerator technologies, safety concepts, and technical infrastructure. It also includes the design of the FCC-hh hadron collider, development of high-field magnets, hadron injector options, and key technical systems for FCC-hh. △ Less

Submitted 25 April, 2025; originally announced May 2025.

Comments: 627 pages. Please address any comment or request to fcc.secretariat@cern.ch

Report number: CERN-FCC-ACC-2025-0004

Future Circular Collider Feasibility Study Report: Volume 3, Civil Engineering, Implementation and Sustainability

Authors: M. Benedikt, F. Zimmermann, B. Auchmann, W. Bartmann, J. P. Burnet, C. Carli, A. Chancé, P. Craievich, M. Giovannozzi, C. Grojean, J. Gutleber, K. Hanke, A. Henriques, P. Janot, C. Lourenço, M. Mangano, T. Otto, J. Poole, S. Rajagopalan, T. Raubenheimer, E. Todesco, L. Ulrici, T. Watson, G. Wilkinson, P. Azzi , et al. (1439 additional authors not shown)

Abstract: Volume 3 of the FCC Feasibility Report presents studies related to civil engineering, the development of a project implementation scenario, and environmental and sustainability aspects. The report details the iterative improvements made to the civil engineering concepts since 2018, taking into account subsurface conditions, accelerator and experiment requirements, and territorial considerations. I… ▽ More Volume 3 of the FCC Feasibility Report presents studies related to civil engineering, the development of a project implementation scenario, and environmental and sustainability aspects. The report details the iterative improvements made to the civil engineering concepts since 2018, taking into account subsurface conditions, accelerator and experiment requirements, and territorial considerations. It outlines a technically feasible and economically viable civil engineering configuration that serves as the baseline for detailed subsurface investigations, construction design, cost estimation, and project implementation planning. Additionally, the report highlights ongoing subsurface investigations in key areas to support the development of an improved 3D subsurface model of the region. The report describes development of the project scenario based on the 'avoid-reduce-compensate' iterative optimisation approach. The reference scenario balances optimal physics performance with territorial compatibility, implementation risks, and costs. Environmental field investigations covering almost 600 hectares of terrain - including numerous urban, economic, social, and technical aspects - confirmed the project's technical feasibility and contributed to the preparation of essential input documents for the formal project authorisation phase. The summary also highlights the initiation of public dialogue as part of the authorisation process. The results of a comprehensive socio-economic impact assessment, which included significant environmental effects, are presented. Even under the most conservative and stringent conditions, a positive benefit-cost ratio for the FCC-ee is obtained. Finally, the report provides a concise summary of the studies conducted to document the current state of the environment. △ Less

Submitted 25 April, 2025; originally announced May 2025.

Comments: 357 pages. Please address any comment or request to fcc.secretariat@cern.ch

Report number: CERN-FCC-ACC-2025-0003

Future Circular Collider Feasibility Study Report: Volume 1, Physics, Experiments, Detectors

Authors: M. Benedikt, F. Zimmermann, B. Auchmann, W. Bartmann, J. P. Burnet, C. Carli, A. Chancé, P. Craievich, M. Giovannozzi, C. Grojean, J. Gutleber, K. Hanke, A. Henriques, P. Janot, C. Lourenço, M. Mangano, T. Otto, J. Poole, S. Rajagopalan, T. Raubenheimer, E. Todesco, L. Ulrici, T. Watson, G. Wilkinson, P. Azzi , et al. (1439 additional authors not shown)

Abstract: Volume 1 of the FCC Feasibility Report presents an overview of the physics case, experimental programme, and detector concepts for the Future Circular Collider (FCC). This volume outlines how FCC would address some of the most profound open questions in particle physics, from precision studies of the Higgs and EW bosons and of the top quark, to the exploration of physics beyond the Standard Model.… ▽ More Volume 1 of the FCC Feasibility Report presents an overview of the physics case, experimental programme, and detector concepts for the Future Circular Collider (FCC). This volume outlines how FCC would address some of the most profound open questions in particle physics, from precision studies of the Higgs and EW bosons and of the top quark, to the exploration of physics beyond the Standard Model. The report reviews the experimental opportunities offered by the staged implementation of FCC, beginning with an electron-positron collider (FCC-ee), operating at several centre-of-mass energies, followed by a hadron collider (FCC-hh). Benchmark examples are given of the expected physics performance, in terms of precision and sensitivity to new phenomena, of each collider stage. Detector requirements and conceptual designs for FCC-ee experiments are discussed, as are the specific demands that the physics programme imposes on the accelerator in the domains of the calibration of the collision energy, and the interface region between the accelerator and the detector. The report also highlights advances in detector, software and computing technologies, as well as the theoretical tools /reconstruction techniques that will enable the precision measurements and discovery potential of the FCC experimental programme. This volume reflects the outcome of a global collaborative effort involving hundreds of scientists and institutions, aided by a dedicated community-building coordination, and provides a targeted assessment of the scientific opportunities and experimental foundations of the FCC programme. △ Less

Submitted 25 April, 2025; originally announced May 2025.

Comments: 290 pages. Please address any comment or request to fcc.secretariat@cern.ch

Report number: CERN-FCC-PHYS-2025-0002

Self-energy correction to the E1 transition amplitudes in hydrogen-like ions

Authors: M. G. Kozlov, M. Y. Kaygorodov, Yu. A. Demidov, V. A. Yerokhin

Abstract: We present calculations of the self-energy correction to the $E1$ transition amplitudes in hydrogen-like ions, performed to all orders in the nuclear binding strength parameter. Our results for the $1s$-$2p_{1/2}$ transition for the hydrogen isoelectronic sequence show that the perturbed-orbital part of the self-energy correction provides the dominant contribution, accounting for approximately 99\… ▽ More We present calculations of the self-energy correction to the $E1$ transition amplitudes in hydrogen-like ions, performed to all orders in the nuclear binding strength parameter. Our results for the $1s$-$2p_{1/2}$ transition for the hydrogen isoelectronic sequence show that the perturbed-orbital part of the self-energy correction provides the dominant contribution, accounting for approximately 99\% of the total correction for this transition. Detailed calculations were performed for $ns$-$n'p$ and $np$-$n'd$ transitions in H-like caesium. We conclude that the perturbed-orbital part remains dominant also for other $ns$-$n'p$ transitions, whereas for the $np$-$n'd$ matrix elements this dominance no longer holds. Consequently, the self-energy corrections for the $np$-$n'd$ one-electron matrix elements cannot be well reproduced by means of effective QED operators constructed for energy levels. △ Less

Submitted 6 February, 2025; v1 submitted 2 December, 2024; originally announced December 2024.

Comments: v2: subsection on frequency-dependent corrections added; 9 pages, 1 figure

Measuring spin-noise correlation function via time reversal

Authors: M. V. Dubinin, A. A. Fomin, G. G. Kozlov, M. Yu. Petrov, V. S. Zapasskii

Abstract: We propose a simple method of measuring the autocorrelation function of a spin noise based on multiplication and averaging two digitized signal traces, with one of them being a time-reversed copy of the other. This procedure allows one to obtain, with lower computational expenses, all the information usually derived in the Fourier transform spin-noise spectroscopy, retaining all the merits of the… ▽ More We propose a simple method of measuring the autocorrelation function of a spin noise based on multiplication and averaging two digitized signal traces, with one of them being a time-reversed copy of the other. This procedure allows one to obtain, with lower computational expenses, all the information usually derived in the Fourier transform spin-noise spectroscopy, retaining all the merits of the latter. We successfully applied this method to the measurements of spin noise in cesium vapors by using a digital oscilloscope in the capacity of the analog-to-digital converter. Specific opportunities of this experimental approach as applied to a more general problem of studying the nature of light-intensity noise are discussed. △ Less

Submitted 21 October, 2024; originally announced October 2024.

Comments: 5 pages, 3 figures

pCI: a parallel configuration interaction software package for high-precision atomic structure calculations

Authors: Charles Cheung, Mikhail G. Kozlov, Sergey G. Porsev, Marianna S. Safronova, Ilya I. Tupitsyn, Andrey I. Bondarev

Abstract: We introduce the pCI software package for high-precision atomic structure calculations. The standard method of calculation is based on the configuration interaction (CI) method to describe valence correlations, but can be extended to attain better accuracy by including core correlations via many-body perturbation theory (CI+MBPT) or the all-order (CI+all-order) method, as well as QED corrections v… ▽ More We introduce the pCI software package for high-precision atomic structure calculations. The standard method of calculation is based on the configuration interaction (CI) method to describe valence correlations, but can be extended to attain better accuracy by including core correlations via many-body perturbation theory (CI+MBPT) or the all-order (CI+all-order) method, as well as QED corrections via QEDMOD. The software package enables calculations of atomic properties, including energy levels, g-factors, hyperfine structure constants, multipole transition matrix elements, polarizabilities, and isotope shifts. It also features modern high-performance computing paradigms, including dynamic memory allocations and large-scale parallelization via the message-passing interface, to optimize and accelerate computations. △ Less

Submitted 9 October, 2024; originally announced October 2024.

Comments: 22 pages, 6 tables, 2 figures

Journal ref: Comput. Phys. Commun. 308, 109463 (2025)

QED calculations of the E1 transition amplitude in neon-like iron and nickel

Authors: M. G. Kozlov, V. A. Yerokhin, M. Y. Kaygorodov., E. V. Tryapitsyna

Abstract: We calculated QED corrections to the $E1$ transition amplitudes in Ne-like iron and nickel. For the $2p \to 3d$ transitions the dominant effect came from the many-electron mixing, or electronic correlations. For the $2p \to 3s$ transitions the correlation and one-electron effects were comparable and tended to compensate each other. Our ab initio calculations showed that vertex corrections were neg… ▽ More We calculated QED corrections to the $E1$ transition amplitudes in Ne-like iron and nickel. For the $2p \to 3d$ transitions the dominant effect came from the many-electron mixing, or electronic correlations. For the $2p \to 3s$ transitions the correlation and one-electron effects were comparable and tended to compensate each other. Our ab initio calculations showed that vertex corrections were negligible for both types of transitions. Other QED corrections were accurately reproduced by including effective QEDMOD operator in the many-electron relativistic configuration interaction calculation. △ Less

Submitted 3 October, 2024; originally announced October 2024.

Comments: 7 pages, no figures

Journal ref: Phys. Rev. A, v. 110, p. 062805 (2024)

Magnetic quadrupole dichroism in isotropic medium

Authors: A. A. Fomin, G. G. Kozlov, M. V. Petrenko, M. Yu. Petrov, D. S. Smirnov, V. S. Zapasskii

Abstract: For isotropic media, the magnetic field applied across the light propagation direction affects their optical properties only in the second order, and its effect proves to be much weaker than in the longitudinal field. In this work, we show that, under resonant excitation well beyond the linear regime, the situation changes drastically: A small magnetic linear anisotropy considerably increases, and… ▽ More For isotropic media, the magnetic field applied across the light propagation direction affects their optical properties only in the second order, and its effect proves to be much weaker than in the longitudinal field. In this work, we show that, under resonant excitation well beyond the linear regime, the situation changes drastically: A small magnetic linear anisotropy considerably increases, and an even stronger new quadrupole dichroism emerges. The latter manifests itself as the 90$^\circ$-periodic azimuthal dependence of the transmission and anisotropic rotation of the probe polarization plane. These effects are described microscopically in a toy model, and their symmetry analysis is presented. Both are observed experimentally on the D2 resonance of cesium vapor and agree with the theoretical predictions. The large magnitude of the quadrupole dichroism makes it promising for magnetometric applications and for studying the effects of anisotropic bleaching. △ Less

Submitted 31 January, 2025; v1 submitted 9 September, 2024; originally announced September 2024.

Comments: 9 pages, 7 figures

Journal ref: Phys. Rev. A 111, 023502 (2025)

Spin-dependent exotic interactions

Authors: Lei Cong, Wei Ji, Pavel Fadeev, Filip Ficek, Min Jiang, Victor V. Flambaum, Haosen Guan, Derek F. Jackson Kimball, Mikhail G. Kozlov, Yevgeny V. Stadnik, Dmitry Budker

Abstract: Novel interactions beyond the four known fundamental forces in nature (electromagnetic, gravitational, strong and weak interactions), may arise due to "new physics" beyond the standard model, manifesting as a "fifth force". This review is focused on spin-dependent fifth forces mediated by exotic bosons such as spin-0 axions and axionlike particles and spin-1 Z' bosons, dark photons, or paraphotons… ▽ More Novel interactions beyond the four known fundamental forces in nature (electromagnetic, gravitational, strong and weak interactions), may arise due to "new physics" beyond the standard model, manifesting as a "fifth force". This review is focused on spin-dependent fifth forces mediated by exotic bosons such as spin-0 axions and axionlike particles and spin-1 Z' bosons, dark photons, or paraphotons. Many of these exotic bosons are candidates to explain the nature of dark matter and dark energy, and their interactions may violate fundamental symmetries. Spin-dependent interactions between fermions mediated by the exchange of exotic bosons have been investigated in a variety of experiments, particularly at the low-energy frontier. Experimental methods and tools used to search for exotic spin-dependent interactions, such as atomic comagnetometers, torsion balances, nitrogen-vacancy spin sensors, and precision atomic and molecular spectroscopy, are described. A complete set of interaction potentials, derived based on quantum field theory with minimal assumptions and characterized in terms of reduced coupling constants, are presented. A comprehensive summary of existing experimental and observational constraints on exotic spin-dependent interactions is given, illustrating the current research landscape and promising directions of further research. △ Less

Submitted 14 October, 2024; v1 submitted 28 August, 2024; originally announced August 2024.

Comments: 100 pages, 16 figures, Invited review submitted to Reviews of Modern Physics (RMP)

Journal ref: Rev. Mod. Phys. 97, 025005 (2025)

Constraints on exotic interactions from scalar spin-spin coupling in tritium deuteride (DT)

Authors: Lei Cong, Derek F. Jackson Kimball, Mikhail G. Kozlov, Dmitry Budker

Abstract: A comparison of theoretical and experimental values of the scalar spin-spin interaction ($J$-coupling) in tritium deuteride molecules yield constraints for nucleon-nucleon exotic interactions of the dimensionless coupling strengths $g_Vg_V$, $g_Ag_A$ and $g_pg_p$, corresponding to the exchange of an vector, axial-vector, and pseudoscalar (axionlike) boson. The couplings between proton ($p$) and nu… ▽ More A comparison of theoretical and experimental values of the scalar spin-spin interaction ($J$-coupling) in tritium deuteride molecules yield constraints for nucleon-nucleon exotic interactions of the dimensionless coupling strengths $g_Vg_V$, $g_Ag_A$ and $g_pg_p$, corresponding to the exchange of an vector, axial-vector, and pseudoscalar (axionlike) boson. The couplings between proton ($p$) and nucleon ($N$), denoted by $g_V^p g_V^N$, $g_p^p g_p^N$ are constrained to be less than $1.4 \times 10^{-6}$ and $2.7\times 10^{-6}$, respectively, for boson masses around 5 keV. The coupling constant $g_A^p g_A^N$ is constrained to be less than $1.0 \times 10^{-18}$ for boson masses $\leq 100$ eV. It is noteworthy that this study represents the first instance in which constraints on $g_V g_V$ have been established through the analysis of the potential term $V_2 + V_3$ for both tritium deuteride and hydrogen deuteride molecules. △ Less

Submitted 29 August, 2024; v1 submitted 27 August, 2024; originally announced August 2024.

Comments: 6 pages, 4 figures

Spectroscopic Shifts in Deuterated Methanol Induced by Variation of me/mp

Authors: J. S. Vorotyntseva, S. A. Levshakov, M. G. Kozlov

Abstract: Numerical calculations of the sensitivity coefficients, Q_mu, of microwave molecular transitions in the ground torsion-rotation state of deuterated methanol (CH3OD, CD3OH, and CD3OD) to small variations in the fundamental physical constant mu = me/mp - the electron-to-proton mass ratio - are reported. Theoretical motivation for changes in mu comes from a variety of models beyond the Standard Model… ▽ More Numerical calculations of the sensitivity coefficients, Q_mu, of microwave molecular transitions in the ground torsion-rotation state of deuterated methanol (CH3OD, CD3OH, and CD3OD) to small variations in the fundamental physical constant mu = me/mp - the electron-to-proton mass ratio - are reported. Theoretical motivation for changes in mu comes from a variety of models beyond the Standard Model of particle physics which are invoked to explain the nature of dark matter and dark energy that dominate the Universe. The calculated values of Q_mu range from -300 to +73 and, thus, make deuterated methanol promising for searches for small space-time changes in mu. It is also shown that among the calculated sensitivity coefficients Q_mu using different Hamiltonians in the present and previous works, there are several pronounced outliers of unclear nature. △ Less

Submitted 13 June, 2024; originally announced June 2024.

Comments: 11 pages, 6 tables, 5 figures, accepted for publication in Phys. Rev. A

Natural-linewidth measurements of the 3C and 3D soft-x-ray transitions in Ni XIX

Authors: Chintan Shah, Steffen Kühn, Sonja Bernitt, René Steinbrügge, Moto Togawa, Lukas Berger, Jens Buck, Moritz Hoesch, Jörn Seltmann, Mikhail G. Kozlov, Sergey G. Porsev, Ming Feng Gu, F. Scott Porter, Thomas Pfeifer, Maurice A. Leutenegger, Charles Cheung, Marianna S. Safronova, José R. Crespo López-Urrutia

Abstract: We used the monochromatic soft-x-ray beamline P04 at the synchrotron-radiation facility PETRA III to resonantly excite the strongest $2p-3d$ transitions in neon-like Ni XIX ions, $[2p^6]_{J=0} \rightarrow [(2p^5)_{1/2}\,3d_{3/2}]_{J=1}$ and $[2p^6]_{J=0} \rightarrow [(2p^5)_{3/2}\,3d_{5/2}]_{J=1}$, respectively dubbed 3C and 3D, achieving a resolving power of 15\,000 and signal-to-background ratio… ▽ More We used the monochromatic soft-x-ray beamline P04 at the synchrotron-radiation facility PETRA III to resonantly excite the strongest $2p-3d$ transitions in neon-like Ni XIX ions, $[2p^6]_{J=0} \rightarrow [(2p^5)_{1/2}\,3d_{3/2}]_{J=1}$ and $[2p^6]_{J=0} \rightarrow [(2p^5)_{3/2}\,3d_{5/2}]_{J=1}$, respectively dubbed 3C and 3D, achieving a resolving power of 15\,000 and signal-to-background ratio of 30. We obtain their natural linewidths, with an accuracy of better than 10\%, as well as the oscillator-strength ratio $f(3C)/f(3D)$ = 2.51(11) from analysis of the resonant fluorescence spectra. These results agree with those of previous experiments, earlier predictions, and our own advanced calculations. △ Less

Submitted 17 June, 2024; v1 submitted 22 April, 2024; originally announced April 2024.

Comments: 10 pages, 3 figures, 3 tables, published

Journal ref: Physical Review A 109, 063108 (2024)

Basis set calculations of heavy atoms

Authors: M. G. Kozlov, Yu. A. Demidov, M. Y. Kaygorodov, E. V. Triapitsyna

Abstract: Most modern calculations of many-electron atoms use basis sets of atomic orbitals. An accurate account for the electronic correlations in heavy atoms is very difficult computational problem and optimization of the basis sets can reduce computational costs and increase final accuracy. Here we suggest a simple differential ansatz to form virtual orbitals from the Dirac-Fock orbitals of the core and… ▽ More Most modern calculations of many-electron atoms use basis sets of atomic orbitals. An accurate account for the electronic correlations in heavy atoms is very difficult computational problem and optimization of the basis sets can reduce computational costs and increase final accuracy. Here we suggest a simple differential ansatz to form virtual orbitals from the Dirac-Fock orbitals of the core and valence electrons. We use basis sets with such orbitals to calculate different properties in Cs including hyperfine structure constants and QED corrections to the valence energies and to the E1 transition amplitudes. △ Less

Submitted 12 December, 2023; originally announced December 2023.

Journal ref: Atoms, 12, 3 (2024)

Spin noise of a halide perovskite

Authors: V. O. Kozlov, N. I. Selivanov, C. C. Stoumpos, G. G. Kozlov, V. S. Zapasskii, Yu. V. Kapitonov, D. S. Smirnov, I. I. Ryzhov

Abstract: We report on first observation of spin noise in a strongly birefringent semiconductor -- halide perovskite single crystal MAPbI$_3$. The observed spin noise resonance is ascribed to free holes with a record spin dephasing time of 4 ns. The spin dynamics is found to be affected by the residual light absorption of the crystal providing renormalization of the Larmor frequency. Extended spin noise spe… ▽ More We report on first observation of spin noise in a strongly birefringent semiconductor -- halide perovskite single crystal MAPbI$_3$. The observed spin noise resonance is ascribed to free holes with a record spin dephasing time of 4 ns. The spin dynamics is found to be affected by the residual light absorption of the crystal providing renormalization of the Larmor frequency. Extended spin noise spectroscopy with rotating magnetic field allowed us not only to evaluate the $g$-factor anisotropy, but also to distinguish two different spin subsystems tentatively associated to twinning of the crystal. △ Less

Submitted 10 November, 2023; originally announced November 2023.

Comments: 14 pages, 11 figures

Comparison of theory and experiment for radiative characteristics in neutral thulium

Authors: Andrey I. Bondarev, Maris Tamanis, Ruvin Ferber, Gönül Başar, Sophie Kröger, Mikhail G. Kozlov, Stephan Fritzsche

Abstract: Intensities in Tm I emission series originating from a common upper level are measured using a Fourier transform spectrometer. The derived relative transition probabilities within each series are compared to the theoretical predictions obtained from large-scale calculations that combine configuration interaction with many-body perturbation theory. Moreover, the Tm I spectrum recorded in an externa… ▽ More Intensities in Tm I emission series originating from a common upper level are measured using a Fourier transform spectrometer. The derived relative transition probabilities within each series are compared to the theoretical predictions obtained from large-scale calculations that combine configuration interaction with many-body perturbation theory. Moreover, the Tm I spectrum recorded in an external magnetic field is analyzed. Our theoretical results well describe the current measurements and show no more than a two-fold difference from previous experimental data on absolute transition probabilities. Additionally, Landé g factors, hyperfine structure constants, and atomic electric quadrupole moments for several levels of interest are computed and compared to experimental observations, where available. △ Less

Submitted 19 December, 2023; v1 submitted 13 October, 2023; originally announced October 2023.

Journal ref: Phys. Rev. A 109, 012815 (2024)

Optically driven spin-alignment precession

Authors: A. A. Fomin, M. Yu. Petrov, A. S. Pazgalev, G. G. Kozlov, V. S. Zapasskii

Abstract: The effect of optically driven spin precession discovered by Bell and Bloom [W. E. Bell and A. L. Bloom, Phys. Rev. Lett. 6, 280 (1961)] is widely used nowadays as a basis for numerous experiments in fundamental physics and for diverse applications. In this paper we consider a much less popular version of the light-induced spin precession that does not imply coherent precession of the spin-system… ▽ More The effect of optically driven spin precession discovered by Bell and Bloom [W. E. Bell and A. L. Bloom, Phys. Rev. Lett. 6, 280 (1961)] is widely used nowadays as a basis for numerous experiments in fundamental physics and for diverse applications. In this paper we consider a much less popular version of the light-induced spin precession that does not imply coherent precession of the spin-system magnetization and is excited by linearly (rather than circularly) polarized light. Pump-probe measurements performed on the D2 line of cesium vapor show that the magnitude of the signal of the optically driven spin-alignment precession, in "vacuum" cells (with no buffer gas) is close to that of classical spin-orientation precession. In the presence of buffer gas, however, the signal of spin-alignment precession appears to be strongly suppressed. The discovered effect is ascribed to spin mixing of excited states of cesium atoms in the cycle of optical pumping. △ Less

Submitted 20 October, 2023; v1 submitted 20 September, 2023; originally announced September 2023.

Comments: 7 pages, 4 figures

Journal ref: Phys. Rev. A 108, 043109 (2023)

Excitation of the $^{229}$Th nucleus by the hole in the inner electronic shells

Authors: M. G. Kozlov, A. V. Oleynichenko, D. Budker, D. A. Glazov, Y. V. Lomachuk, V. M. Shabaev, A. V. Titov, I. I. Tupitsyn, A. V. Volotka

Abstract: The $^{229}$Th nucleus has a long-lived isomeric state $A^*$ at 8.338(24) eV [Kraemer et al, Nature, \textbf{617}, 706 (2023)]. This state is connected to the ground state by an M1 transition. For a hydrogenlike Th ion in the $1s$ state the hyperfine structure splitting is about 0.7 eV. This means that the hyperfine interaction can mix the nuclear ground state with the isomeric state with a mixing… ▽ More The $^{229}$Th nucleus has a long-lived isomeric state $A^*$ at 8.338(24) eV [Kraemer et al, Nature, \textbf{617}, 706 (2023)]. This state is connected to the ground state by an M1 transition. For a hydrogenlike Th ion in the $1s$ state the hyperfine structure splitting is about 0.7 eV. This means that the hyperfine interaction can mix the nuclear ground state with the isomeric state with a mixing coefficient $β$ about 0.03. If the electron is suddenly removed from this system, the nucleus will be left in the mixed state. The probability to find the nucleus in the isomeric state $A^*$ is equal to $β^2\sim 10^{-3}$. For the $2s$ state the effect is roughly two orders of magnitude smaller. An atom with a hole in the $1s$ or $2s$ shell is similar to the hydrogenlike atom, only the hole has a short lifetime $τ$. After the hole is filled, there is a non-zero probability to find the nucleus in the $A^*$ state. Estimates of this probability are presented along with a discussion of possible experiments on Th-doped xenotime-type orthophosphate crystals and other broad band gap materials. △ Less

Submitted 1 March, 2024; v1 submitted 9 August, 2023; originally announced August 2023.

Comments: 6 pages, 1 figure. V.2: Sec. IV and references added

Optically stimulated electron paramagnetic resonance: simplicity, versatility, information content

Authors: V. O. Kozlov, A. A. Fomin, I. I. Ryzhov, G. G. Kozlov

Abstract: A simple technique for observing optically stimulated electron paramagnetic resonance (OSEPR) is proposed and investigated. The versatility and information content of the described technique is demonstrated by the example of the OSEPR spectra of systems that are unpopular for this type of spectroscopy: a crystal with rare-earth ions Nd$^{3+}$ and a doped semiconductor GaAs. In addition, the OSEPR… ▽ More A simple technique for observing optically stimulated electron paramagnetic resonance (OSEPR) is proposed and investigated. The versatility and information content of the described technique is demonstrated by the example of the OSEPR spectra of systems that are unpopular for this type of spectroscopy: a crystal with rare-earth ions Nd$^{3+}$ and a doped semiconductor GaAs. In addition, the OSEPR spectrum of atomic cesium is presented, in which an optical nonlinearity is observed that makes it possible to estimate the Rabi frequency for the relevant optical transition. The effects observed in the described experiments (switching of peaks to dips, light-induced splitting of the OSEPR lines, and the appearance of a spectral feature at the double-Larmor frequency) are interpreted using the model proposed in the theoretical part of the work. The suggested interpretation shows the possibility of using the described OSEPR technique to estimate not only `magnetic' parameters of the model Hamiltonian (g-factors, spin relaxation times), but also the Rabi frequencies characterizing optical transitions. △ Less

Submitted 28 June, 2023; originally announced June 2023.

Contribution of negative-energy states to multipolar polarizabilities of the Sr optical lattice clock

Authors: S. G. Porsev, M. G. Kozlov, M. S. Safronova

Abstract: We address the problem of lattice light shifts in the Sr clock caused by multipolar M1 and E2 atom-field interactions. We presented a simple but accurate formula for the magnetic-dipole polarizability that takes into account both the positive and negative energy states contributions. We calculated the contribution of negative energy states to the M1 polarizabilities of the clock 1S0 and 3P0 states… ▽ More We address the problem of lattice light shifts in the Sr clock caused by multipolar M1 and E2 atom-field interactions. We presented a simple but accurate formula for the magnetic-dipole polarizability that takes into account both the positive and negative energy states contributions. We calculated the contribution of negative energy states to the M1 polarizabilities of the clock 1S0 and 3P0 states at the magic frequency. Taking these contributions into account, we obtained good agreement with the experimental results, resolving the major discrepancy between the theory and the experiment △ Less

Submitted 16 June, 2023; originally announced June 2023.

Comments: 5 pages

The Bohr-Weisskopf effect in the potassium isotopes

Authors: Yu. A. Demidov, M. G. Kozlov, A. E. Barzakh, V. A. Yerokhin

Abstract: The magnetic hyperfine structure constants have been calculated for low-lying levels in neutral potassium atom taking into account the Bohr--Weisskopf (BW) and Breit--Rosenthal (BR) effects. According to our results the $4p_{1/2}$ state of K~I is free from both BR and BW corrections on the level of the current theoretical uncertainties. Using this finding and the measured values of the… ▽ More The magnetic hyperfine structure constants have been calculated for low-lying levels in neutral potassium atom taking into account the Bohr--Weisskopf (BW) and Breit--Rosenthal (BR) effects. According to our results the $4p_{1/2}$ state of K~I is free from both BR and BW corrections on the level of the current theoretical uncertainties. Using this finding and the measured values of the $A(4p_{1/2})$ constants, we corrected the nuclear magnetic moments for several short-lived potassium isotopes. The BW correction is represented as a product of atomic and nuclear factors. We calculated the atomic factor for the ground state of K I, which allowed us to extract nuclear factors for potassium $I^π= 3/2^+$ isotopes from the experimental data. In this way the application range of the single-particle nuclear model for nuclear-factor calculation in these isotopes has been clarified. △ Less

Submitted 21 November, 2022; originally announced November 2022.

Using parity-nonconserving spin-spin coupling to measure the Tl nuclear anapole moment in a TlF molecular beam

Authors: John W. Blanchard, Dmitry Budker, David DeMille, Mikhail G. Kozlov, Leonid V. Skripnikov

Abstract: An experiment utilizing a TlF molecular beam is being developed by the CeNTREX collaboration to search for hadronic interactions that violate both time-reversal (T) and parity (P) invariance. Here we propose to use the same beam to look for a T-invariance conserving but P-nonconserving (PNC) effect induced by the anapole moment of the Tl nucleus, via a vector coupling of the two nuclear spins in T… ▽ More An experiment utilizing a TlF molecular beam is being developed by the CeNTREX collaboration to search for hadronic interactions that violate both time-reversal (T) and parity (P) invariance. Here we propose to use the same beam to look for a T-invariance conserving but P-nonconserving (PNC) effect induced by the anapole moment of the Tl nucleus, via a vector coupling of the two nuclear spins in TlF. To measure the nuclear anapole moment, the dc electric and magnetic fields in CeNTREX are replaced by rf fields resonant with a nuclear spin flip transition. We adapt the relativistic coupled cluster method in a combination with relativistic density functional theory for the calculation of the molecular PNC spin-spin vector coupling constant that links the experimental signal with the anapole moment. The value of the P-conserving spin-spin coupling constant calculated within the same approach is found to be in good agreement with available experimental data. △ Less

Submitted 14 May, 2023; v1 submitted 30 October, 2022; originally announced October 2022.

Journal ref: Phys. Rev. Research 5, 013191 (2023)

Bremsstrahlung on noble gases at low energies

Authors: A. I. Milstein, S. G. Salnikov, M. G. Kozlov

Abstract: A detailed analysis of the bremsstrahlung spectrum at nonrelativistic electron scattering on argon and xenon is carried out. It is shown that the approximate formulas widely used for the description of bremsstrahlung spectra lead to predictions that significantly differ from the exact results. In the limit when the photon frequency tends to zero, a rigorous proof of the relationship between the sp… ▽ More A detailed analysis of the bremsstrahlung spectrum at nonrelativistic electron scattering on argon and xenon is carried out. It is shown that the approximate formulas widely used for the description of bremsstrahlung spectra lead to predictions that significantly differ from the exact results. In the limit when the photon frequency tends to zero, a rigorous proof of the relationship between the spectrum of the bremsstrahlung with a transport cross section of electron scattering on an atom is given. This proof does not require any assumptions about the dependence of the scattering phases on energy. For electron energies lower than the luminescence threshold, it is shown that the predictions for a number of radiated photons obtained by the exact formula are in good agreement with the available experimental data. △ Less

Submitted 12 July, 2022; v1 submitted 3 June, 2022; originally announced June 2022.

Comments: 15 pages, 5 figures, new section on the angular distributions is added

Journal ref: Nucl. Instruments Methods Phys. Res. Sect. B Beam Interact. with Mater. Atoms 530, 48 (2022)

Combination of the Perturbation Theory with Configuration Interaction Method

Authors: M. G. Kozlov, I. I. Tupitsyn, A. I. Bondarev, D. V. Mironova

Abstract: Present atomic theory provides accurate and reliable results for atoms with a small number of valence electrons. However, most current methods of calculations fail when the number of valence electrons exceeds four or five. This means that we can not make reliable predictions for more than a half of the periodic table. Here we suggest a modification of the CI+MBPT (configuration interaction plus ma… ▽ More Present atomic theory provides accurate and reliable results for atoms with a small number of valence electrons. However, most current methods of calculations fail when the number of valence electrons exceeds four or five. This means that we can not make reliable predictions for more than a half of the periodic table. Here we suggest a modification of the CI+MBPT (configuration interaction plus many-body perturbation theory) method, which may be applicable to atoms and ions with filling d and f shells. △ Less

Submitted 4 February, 2022; originally announced February 2022.

Comments: 11 pages, 6 figures, submitted to PRA

Journal ref: Phys. Rev. A 105, 052805 (2022)

New Measurement Resolves Key Astrophysical Fe XVII Oscillator Strength Problem

Authors: Steffen Kühn, Charles Cheung, Natalia S. Oreshkina, René Steinbrügge, Moto Togawa, Sonja Bernitt, Lukas Berger, Jens Buck, Moritz Hoesch, Jörn Seltmann, Florian Trinter, Christoph H. Keitel, Mikhail G. Kozlov, Sergey G. Porsev, Ming Feng Gu, F. Scott Porter, Thomas Pfeifer, Maurice A. Leutenegger, Zoltán Harman, Marianna S. Safronova, José R. Crespo López-Urrutia, Chintan Shah

Abstract: One of the most enduring and intensively studied problems of X-ray astronomy is the disagreement of state-of-the art theory and observations for the intensity ratio of two Fe XVII transitions of crucial value for plasma diagnostics, dubbed 3C and 3D. We unravel this conundrum at the PETRA III synchrotron facility by increasing the resolving power two and a half times and the signal-to-noise ratio… ▽ More One of the most enduring and intensively studied problems of X-ray astronomy is the disagreement of state-of-the art theory and observations for the intensity ratio of two Fe XVII transitions of crucial value for plasma diagnostics, dubbed 3C and 3D. We unravel this conundrum at the PETRA III synchrotron facility by increasing the resolving power two and a half times and the signal-to-noise ratio thousand-fold compared to our previous work. The Lorentzian wings had hitherto been indistinguishable from the background and were thus not modeled, resulting in a biased line-strength estimation. The present experimental oscillator-strength ratio $R_\mathrm{exp}=f_{\mathrm{3C}}/f_{\mathrm{3D}}=3.51(2)_{\mathrm{stat}}(7)_{\mathrm{sys}}$ agrees with our state-of-the-art calculation of $R_\mathrm{th}=3.55(2)$, as well as with some previous theoretical predictions. To further rule out any uncertainties associated with the measured ratio, we also determined the individual natural linewidths and oscillator strengths of 3C and 3D transitions, which also agree well with the theory. This finally resolves the decades-old mystery of Fe XVII oscillator strengths. △ Less

Submitted 6 December, 2022; v1 submitted 22 January, 2022; originally announced January 2022.

Comments: Main manuscript and supplemental material at https://journals.aps.org/prl/supplemental/10.1103/PhysRevLett.129.245001/LN17392_Supplemental_Material.pdf

Journal ref: Physical Review Letters 129, 245001 (2022)

Laser Spectroscopy of the y$^7$P$_J^{\circ}$ states of Cr I

Authors: E. B. Norrgard, D. S. Barker, S. P. Eckel, S. G. Porsev, C. Cheung, M. G. Kozlov, I. I. Tupitsyn, M. S. Safronova

Abstract: Here we report measured and calculated values of decay rates of the 3d$^4$($^5$D)4s4p($^3$P$^{\rm{o}}$)\ y$^7$P$^{\rm{o}}_{2,3,4}$ states of Cr I. The decay rates are measured using time-correlated single photon counting with roughly 1% total uncertainty. In addition, the isotope shifts for these transitions are measured by laser induced fluorescence to roughly 0.5% uncertainty. The decay rate cal… ▽ More Here we report measured and calculated values of decay rates of the 3d$^4$($^5$D)4s4p($^3$P$^{\rm{o}}$)\ y$^7$P$^{\rm{o}}_{2,3,4}$ states of Cr I. The decay rates are measured using time-correlated single photon counting with roughly 1% total uncertainty. In addition, the isotope shifts for these transitions are measured by laser induced fluorescence to roughly 0.5% uncertainty. The decay rate calculations are carried out by a hybrid approach that combines configuration interaction and the linearized coupled cluster method (CI+all-order method). The measurements provide a much needed precision benchmark for testing the accuracy of the CI+all-order approach for such complicated systems with six valence electrons, allowing to significantly expand its applicability. These measurements also demonstrate operation of a cryogenic buffer gas beam source for future experiments with MgF molecules toward quantum blackbody thermometry. △ Less

Submitted 23 November, 2021; originally announced November 2021.

Precision calculation of hyperfine constants for extracting nuclear moments of 229Th

Authors: S. G. Porsev, M. S. Safronova, M. G. Kozlov

Abstract: Determination of nuclear moments for many nuclei relies on the computation of hyperfine constants, with theoretical uncertainties directly affecting the resulting uncertainties of the nuclear moments. In this work we improve the precision of such method by including for the first time an iterative solution of equations for the core triple cluster amplitudes into the relativistic coupled-cluster me… ▽ More Determination of nuclear moments for many nuclei relies on the computation of hyperfine constants, with theoretical uncertainties directly affecting the resulting uncertainties of the nuclear moments. In this work we improve the precision of such method by including for the first time an iterative solution of equations for the core triple cluster amplitudes into the relativistic coupled-cluster method, with large-scale complete basis sets. We carried out calculations of the energies and magnetic dipole and electric quadrupole hyperfine structure constants for the low-lying states of 229Th^(3+) in the framework of such relativistic coupled-cluster single double triple (CCSDT) method. We present a detailed study of various corrections to all calculated properties. Using the theory results and experimental data we found the nuclear magnetic dipole and electric quadrupole moments to be mu = 0.366(6)*mu_N and Q = 3.11(2) eb, and reducing the uncertainty of the quadrupole moment by a factor of three. The Bohr-Weisskopf effect of the finite nuclear magnetization is investigated, with bounds placed on the deviation of the magnetization distribution from the uniform one. △ Less

Submitted 30 July, 2021; originally announced July 2021.

Comments: 6 pages, 1 fugure

Invariants in the paramagnetic resonance spectra of impurity crystals

Authors: A. N. Kamenskii, V. O. Kozlov, N. S. Kuznetsov, I. I. Ryzhov, G. G. Kozlov, M. Bayer, A. Greilich, V. S. Zapasskii

Abstract: We show that in cubic crystals with anisotropic impurity centers the sum of squares of the magnetic resonance (EPR) frequencies is invariant with respect to the magnetic field direction. The connection between such an invariant and the g-tensor components of the impurity is derived for different types of centers. The established regularity is confirmed experimentally for the spin-noise spectra of… ▽ More We show that in cubic crystals with anisotropic impurity centers the sum of squares of the magnetic resonance (EPR) frequencies is invariant with respect to the magnetic field direction. The connection between such an invariant and the g-tensor components of the impurity is derived for different types of centers. The established regularity is confirmed experimentally for the spin-noise spectra of a CaF2-Nd3+ crystal. We show how this property of the EPR spectra can be efficiently used for the assignment of paramagnetic centers in cubic crystals. △ Less

Submitted 23 June, 2021; originally announced June 2021.

Comments: 5 pages, 2 figures

Anomalous light-induced broadening of the spin-noise resonance in cesium vapor

Authors: A. A. Fomin, M. Yu. Petrov, G. G. Kozlov, A. K. Vershovskii, M. M. Glazov, V. S. Zapasskii

Abstract: We uncover a highly nontrivial dependence of the spin-noise (SN) resonance broadening induced by the intense probe beam. The measurements were performed by probing the cell with cesium vapor at the wavelengths of the transition ${6}^2S_{1/2} \leftrightarrow {6}^2P_{3/2}$ ($\mathrm{D}_2$ line) with the unresolved hyperfine structure of the excited state. The light-induced broadening of the SN reson… ▽ More We uncover a highly nontrivial dependence of the spin-noise (SN) resonance broadening induced by the intense probe beam. The measurements were performed by probing the cell with cesium vapor at the wavelengths of the transition ${6}^2S_{1/2} \leftrightarrow {6}^2P_{3/2}$ ($\mathrm{D}_2$ line) with the unresolved hyperfine structure of the excited state. The light-induced broadening of the SN resonance was found to differ strongly at different slopes of the $\mathrm{D}_2$ line and, generally, varied nonmonotonically with light power. We discuss the effect in terms of the phenomenological Bloch equations for the spin fluctuations and demonstrate that the SN broadening behavior strongly depends on the relation between the pumping and excited-level decay rates, the spin precession, and decoherence rates. To reconcile the puzzling experimental results, we propose that the degree of optical perturbation of the spin-system is controlled by the route of the excited-state relaxation of the atom or, in other words, that the act of optical excitation of the atom does not necessarily break down completely its ground-state coherence and continuity of the spin precession. Spectral asymmetry of the effect, in this case, is provided by the position of the "closed" transition $F = 4 \leftrightarrow F' = 5$ at the short-wavelength side of the line. This hypothesis, however, remains to be proven by microscopic calculations. △ Less

Submitted 29 April, 2021; v1 submitted 2 February, 2021; originally announced February 2021.

Comments: 9 pages, 9 figures, revised version

Journal ref: Phys. Rev. A 103, 042820 (2021)

Raman scattering model of the spin noise

Authors: G. G. Kozlov, A. A. Fomin, M. Yu. Petrov, I. I. Ryzhov, V. S. Zapasskii

Abstract: The mechanism of formation of the polarimetric signal observed in the spin noise spectroscopy (SNS) is analyzed from the viewpoint of the light scattering theory. A rigorous calculation of the polarimetric signal (Faraday rotation or ellipticity) recorded in the SNS is presented in the approximation of single scattering. We show that it is most correctly to consider this noise as a result of scatt… ▽ More The mechanism of formation of the polarimetric signal observed in the spin noise spectroscopy (SNS) is analyzed from the viewpoint of the light scattering theory. A rigorous calculation of the polarimetric signal (Faraday rotation or ellipticity) recorded in the SNS is presented in the approximation of single scattering. We show that it is most correctly to consider this noise as a result of scattering of the probe light beam by fluctuating susceptibility of the medium. Fluctuations of the gyrotropic (antisymmetric) part of the susceptibility tensor lead to appearance of the typical for the SNS Faraday rotation noise at the Larmor frequency. At the same time, fluctuations of linear anisotropy of the medium (symmetric part of the susceptibility tensor) give rise to the ellipticity noise of the probe beam spectrally localized at the double Larmor frequency. The results of the theoretical analysis well agree with the experimental data on the ellipticity noise in cesium vapor. △ Less

Submitted 1 February, 2021; originally announced February 2021.

Comments: arXiv admin note: substantial text overlap with arXiv:2002.06035

Journal ref: Opt. Express 29, 4770 (2021)

Nonlinear spectroscopy of high-spin fluctuations

Authors: A. A. Fomin, M. Yu. Petrov, I. I. Ryzhov, G. G. Kozlov, V. S. Zapasskii, M. M. Glazov

Abstract: We investigate theoretically and experimentally fluctuations of high spin (F>1/2) beyond the linear response regime and demonstrate dramatic modifications of the spin noise spectra in the high power density probe field. Several effects related to an interplay of high spin and perturbation are predicted theoretically and revealed experimentally, including strong sensitivity of the spin noise spectr… ▽ More We investigate theoretically and experimentally fluctuations of high spin (F>1/2) beyond the linear response regime and demonstrate dramatic modifications of the spin noise spectra in the high power density probe field. Several effects related to an interplay of high spin and perturbation are predicted theoretically and revealed experimentally, including strong sensitivity of the spin noise spectra to the mutual orientation of the probe polarization plane and magnetic field direction, appearance of high harmonics of the Larmor frequency in the spin noise and the fine structure of the Larmor peaks. We demonstrate the ability of the spin-noise spectroscopy to access the nonlinear effects related to the renormalization of the spin states by strong electromagnetic fields. △ Less

Submitted 1 February, 2021; originally announced February 2021.

Probing fast oscillating scalar dark matter with atoms and molecules

Authors: Dionysios Antypas, Oleg Tretiak, Ke Zhang, Antoine Garcon, Gilad Perez, Mikhail G. Kozlov, Stephan Schiller, Dmitry Budker

Abstract: Light scalar Dark Matter with scalar couplings to matter is expected within several scenarios to induce variations in the fundamental constants of nature. Such variations can be searched for, among other ways, via atomic spectroscopy. Sensitive atomic observables arise primarily due to possible changes in the fine-structure constant or the electron mass. Most of the searches to date have focused o… ▽ More Light scalar Dark Matter with scalar couplings to matter is expected within several scenarios to induce variations in the fundamental constants of nature. Such variations can be searched for, among other ways, via atomic spectroscopy. Sensitive atomic observables arise primarily due to possible changes in the fine-structure constant or the electron mass. Most of the searches to date have focused on slow variations of the constants (i.e. modulation frequencies $<$ 1 Hz). In a recent experiment \mbox{[Phys. Rev. Lett. 123, 141102 (2019)]} called WReSL (Weekend Relaxion-Search Laboratory), we reported on a direct search for rapid variations in the radio-frequency band. Such a search is particularly motivated within a class of relaxion Dark Matter models. We discuss the WReSL experiment, report on progress towards improved measurements of rapid fundamental constant variations, and discuss the planned extension of the work to molecules, in which rapid variations of the nuclear mass can be sensitively searched for. △ Less

Submitted 28 January, 2021; v1 submitted 2 December, 2020; originally announced December 2020.

Comments: 15 pages, 4 figures

Atomic calculations of hyperfine structure anomaly in gold

Authors: Yu. A. Demidov, E. A. Konovalova, R. T. Imanbaeva, M. G. Kozlov, A. E. Barzakh

Abstract: The magnetic hyperfine structure constants have been calculated for low-lying levels in neutral gold atom and gold-like ion of mercury taking into account Bohr--Weisskopf (BW) effect. BW effect is represented as a product of atomic and nuclear ($d_\mathrm{nuc}$) factors. We have calculated the atomic factors, which enable one to extract BW-correction values for far from stability gold nuclei from… ▽ More The magnetic hyperfine structure constants have been calculated for low-lying levels in neutral gold atom and gold-like ion of mercury taking into account Bohr--Weisskopf (BW) effect. BW effect is represented as a product of atomic and nuclear ($d_\mathrm{nuc}$) factors. We have calculated the atomic factors, which enable one to extract BW-correction values for far from stability gold nuclei from the experimental data. The possible uncertainty of our atomic calculations have been estimated by the comparison with the available experimental data. It has been shown that the standard single-particle approach in $d_\mathrm{nuc}$ calculation reasonably well describes experimental data for $11/2^-$ gold isomers and $3/2^+$ ground state of $\rm ^{199}Au$. At the same time, it fails to describe the hyperfine constant in $^{197}\mathrm{Au}$. This indicates the more pronounced configuration mixing in $\rm ^{197}Au$ than in $\rm ^{199}Au$. △ Less

Submitted 7 March, 2021; v1 submitted 1 December, 2020; originally announced December 2020.

Journal ref: Phys. Rev. A 103, 032824 (2021)

Sensing: Equation One

Authors: Dmitry Budker, Mikhail G. Kozlov

Abstract: Spin projection noise sets a limit for the sensitivity of spin-based magnetometers and experiments searching for parity- and time-reversal-invariance-violating dipole moments. The limit is described by a simple equation that appears to have universal applicability. Spin projection noise sets a limit for the sensitivity of spin-based magnetometers and experiments searching for parity- and time-reversal-invariance-violating dipole moments. The limit is described by a simple equation that appears to have universal applicability. △ Less

Submitted 22 November, 2020; originally announced November 2020.

Comments: 5 pages, 1 figure

Predicting quasibound states of negative ions

Authors: M. S. Safronova, C. Cheung, M. G. Kozlov, S. E. Spielman, N. D. Gibson, C. W. Walter

Abstract: We demonstrated the accurate prediction of a quasibound spectrum of a negative ion using a novel high-precision theoretical approach. We used La$^-$ as a test case due to a recent experiment that measured energies of 11 resonances in its photodetachment spectrum attributed to transitions to quasibound states [C. W. Walter et al., PRA, in press (2020); arXiv:2010.01122]. We identified all of the ob… ▽ More We demonstrated the accurate prediction of a quasibound spectrum of a negative ion using a novel high-precision theoretical approach. We used La$^-$ as a test case due to a recent experiment that measured energies of 11 resonances in its photodetachment spectrum attributed to transitions to quasibound states [C. W. Walter et al., PRA, in press (2020); arXiv:2010.01122]. We identified all of the observed resonances, and predicted one more peak just outside the range of the prior experiment. Following the theoretical prediction, the peak was observed at the predicted wavelength, validating the identification. The same approach is applicable to a wide range of negative ions. Moreover, theory advances reported in this work can be used for massive generation of atomic transition properties for neutrals and positive ions needed for a variety of applications. △ Less

Submitted 6 October, 2020; originally announced October 2020.

Comments: 6 pages, 3 figures

Journal ref: Phys. Rev. A 103, 022819 (2021)

Parity nonconserving interactions of electrons in chiral molecules with cosmic fields

Authors: Konstantin Gaul, Mikhail G. Kozlov, Timur A. Isaev, Robert Berger

Abstract: Pseudoscalar or pseudovector cosmic fields, that serve as a source of parity ($\mathcal{P}$) violation, are invoked in different models for cold dark matter or in the standard model extension that allows for Lorentz invariance violation. A direct detection of the timelike-component of such fields requires a direct measurement of $\mathcal{P}$-odd potentials or their evolution over time. Herein, ad… ▽ More Pseudoscalar or pseudovector cosmic fields, that serve as a source of parity ($\mathcal{P}$) violation, are invoked in different models for cold dark matter or in the standard model extension that allows for Lorentz invariance violation. A direct detection of the timelike-component of such fields requires a direct measurement of $\mathcal{P}$-odd potentials or their evolution over time. Herein, advantageous properties of chiral molecules, in which $\mathcal{P}$-odd potentials lead to resonance frequency differences between enantiomers, for direct detection of such $\mathcal{P}$-odd cosmic fields are demonstrated. Scaling behavior of electronic structure enhancements of such interactions with respect to nuclear charge number and the fine-structure constant is derived analytically. This allows a simple estimate of the effect sizes for arbitrary molecules. The analytical derivation is supported by quasi-relativistic numerical calculations in the molecules H$_2$X$_2$ and H$_2$XO with X $=$ O, S, Se, Te, Po. Parity violating effects due to cosmic fields on the C--F stretching mode in CHBrClF are compared to electroweak parity violation and influences of non-separable anharmonic vibrational corrections are discussed. On this basis it was estimated from a twenty year old experiment with CHBrClF that bounds on Lorentz invariance violation as characterized by the parameter $|b^\mathrm{e}_0|$ can be pushed down to the order of $10^{-17}\,\mathrm{GeV}$ in modern experiments with suitably selected molecular system, which will be an improvement of the current best limits by at least two orders of magnitude. This serves to highlight the particular opportunities that precision spectroscopy of chiral molecules provides in the search for new physics beyond the standard model. △ Less

Submitted 8 May, 2020; originally announced May 2020.

Comments: 16 pages, 6 tables, 5 figures

Journal ref: Phys. Rev. A 102, 032816 (2020)

Detection of missing low-lying atomic states in actinium

Authors: Ke Zhang, Dominik Studer, Felix Weber, Vadim M. Gadelshin, Nina Kneip, Sebastian Raeder, Dmitry Budker, Klaus Wendt, Tom Kieck, Sergey G. Porsev, Charles Cheung, Marianna S. Safronova, Mikhail G. Kozlov

Abstract: Two lowest-energy odd-parity atomic levels of actinium, 7s^27p 2P^o_1/2, 7s^27p 2P^o_3/2, were observed via two-step resonant laser-ionization spectroscopy and their respective energies were measured to be 7477.36(4) cm^-1 and 12 276.59(2) cm^-1. The lifetimes of these states were determined as 668(11) ns and 255(7) ns, respectively. In addition, these properties were calculated using a hybrid app… ▽ More Two lowest-energy odd-parity atomic levels of actinium, 7s^27p 2P^o_1/2, 7s^27p 2P^o_3/2, were observed via two-step resonant laser-ionization spectroscopy and their respective energies were measured to be 7477.36(4) cm^-1 and 12 276.59(2) cm^-1. The lifetimes of these states were determined as 668(11) ns and 255(7) ns, respectively. In addition, these properties were calculated using a hybrid approach that combines configuration interaction and coupled-cluster methods in good agreement. The data are of relevance for understanding the complex atomic spectra of actinides and for developing efficient laser-cooling and ionization schemes for actinium, with possible applications for high-purity medicalisotope production and future fundamental physics experiments with this atom. △ Less

Submitted 7 May, 2020; originally announced May 2020.

Comments: 6pages, 5figures

Journal ref: Phys. Rev. Lett. 125, 073001 (2020)

Chiral molecules as sensitive probes for direct detection of $\mathcal{P}$-odd cosmic fields

Authors: Konstantin Gaul, Mikhail G. Kozlov, Timur A. Isaev, Robert Berger

Abstract: Particular advantages of chiral molecules for direct detection of the time-dependence of pseudoscalar and the timelike-component of pseudovector cosmic fields are highlighted. Such fields are invoked in different models for cold dark matter or in the Lorentz-invariance violating standard model extensions and thus are signatures of physics beyond the standard model. The sensitivity of a twenty year… ▽ More Particular advantages of chiral molecules for direct detection of the time-dependence of pseudoscalar and the timelike-component of pseudovector cosmic fields are highlighted. Such fields are invoked in different models for cold dark matter or in the Lorentz-invariance violating standard model extensions and thus are signatures of physics beyond the standard model. The sensitivity of a twenty year old experiment with the molecule CHBrClF to pseudovector cosmic fields as characterized by the parameter $|b^\mathrm{e}_0|$ is estimated to be $\mathcal{O}(10^{-12}\,\mathrm{GeV})$ and allows to predict the sensitivity of future experiments with favorable choices of chiral molecular probes to be $\mathcal{O}(10^{-17}\,\mathrm{GeV})$, which will be an improvement of the present best limits by at least two orders of magnitude. △ Less

Submitted 5 May, 2020; originally announced May 2020.

Comments: 6 pages, 2 figures

Journal ref: Phys. Rev. Lett. 125, 123004 (2020)

Calculation of hyperfine magnetic anomaly in many-electron atoms

Authors: E. A. Konovalova, Yu. A. Demidov, M. G. Kozlov

Abstract: The precision measurements of the ratio of hyperfine structure constants for $s_{1/2}$ and $p_{1/2}$ states allow us to estimate the difference between hyperfine magnetic anomalies for these levels. We calculate the atomic factor in order to recover the absolute values of the hyperfine magnetic anomalies from their difference. Taking into account the hyperfine anomaly correction allows one to incr… ▽ More The precision measurements of the ratio of hyperfine structure constants for $s_{1/2}$ and $p_{1/2}$ states allow us to estimate the difference between hyperfine magnetic anomalies for these levels. We calculate the atomic factor in order to recover the absolute values of the hyperfine magnetic anomalies from their difference. Taking into account the hyperfine anomaly correction allows one to increase the accuracy of determining the g-factors of short-lived isotopes by more than an order of magnitude. △ Less

Submitted 25 April, 2020; originally announced April 2020.

Optical clocks based on the Cf$^{15+}$ and Cf$^{17+}$ ions

Authors: S. G. Porsev, U. I. Safronova, M. S. Safronova, P. O. Schmidt, A. I. Bondarev, M. G. Kozlov, I. I. Tupitsyn

Abstract: Recent experimental progress in cooling, trapping, and quantum logic spectroscopy of highly-charged ions (HCIs) made HCIs accessible for high resolution spectroscopy and precision fundamental studies. Based on these achievements, we explore a possibility to develop optical clocks using transitions between the ground and a low-lying excited state in the Cf$^{15+}$ and Cf$^{17+}$ ions. Using a high-… ▽ More Recent experimental progress in cooling, trapping, and quantum logic spectroscopy of highly-charged ions (HCIs) made HCIs accessible for high resolution spectroscopy and precision fundamental studies. Based on these achievements, we explore a possibility to develop optical clocks using transitions between the ground and a low-lying excited state in the Cf$^{15+}$ and Cf$^{17+}$ ions. Using a high-accuracy relativistic method of calculation we predicted the wavelengths of clock transitions, calculated relevant atomic properties, and analyzed a number of systematic effects (such as the electric quadrupole-, micromotion-, and quadratic Zeeman shifts of the clock transitions) that affect the accuracy and stability of the optical clocks. We also calculated magnetic dipole hyperfine-structure constants of the clock states and the blackbody radiation shifts of the clock transitions. △ Less

Submitted 13 April, 2020; originally announced April 2020.

Comments: 9 pages, 2 figures

Journal ref: Phys. Rev. A 102, 012802 (2020)

Polarimetric observation of noise of linear birefringence of cesium atomic vapors spectrally localized at double Larmor frequency in a magnetic field

Authors: G. G. Kozlov, A. A. Fomin, M. Yu. Petrov, V. S. Zapasskii

Abstract: We study radio-frequency spectrum of ellipticity noise of a probe laser beam transmitted through a cell with cesium vapor in a magnetic field. The experimental results are interpreted in terms of the model proposed by Gorbovitskii and Perel (Opt. Spektrosc. 54, 388 (1983)) according to which the observed noise arises due to heterodyning of the light scattered by fluctuations of the tensor $ α$ of… ▽ More We study radio-frequency spectrum of ellipticity noise of a probe laser beam transmitted through a cell with cesium vapor in a magnetic field. The experimental results are interpreted in terms of the model proposed by Gorbovitskii and Perel (Opt. Spektrosc. 54, 388 (1983)) according to which the observed noise arises due to heterodyning of the light scattered by fluctuations of the tensor $ α$ of optical susceptibility of cesium vapor. We show, both experimentally and theoretically, that, in the noise measurements if this kind, along with fluctuations of the antisymmetric (gyrotropic) part of the tensor $ α$ at the Larmor frequency, may be observed fluctuations of its symmetric part, corresponding to fluctuations of linear birefringence (alignment) of the atomic system. The polarization noise provided by these fluctuations is localized spectrally at the double Larmor frequency. △ Less

Submitted 14 February, 2020; originally announced February 2020.

Comments: 8 pages, 3 figures

Technical Design Report for the PANDA Endcap Disc DIRC

Authors: Panda Collaboration, F. Davi, W. Erni, B. Krusche, M. Steinacher, N. Walford, H. Liu, Z. Liu, B. Liu, X. Shen, C. Wang, J. Zhao, M. Albrecht, T. Erlen, F. Feldbauer, M. Fink, V. Freudenreich, M. Fritsch, F. H. Heinsius, T. Held, T. Holtmann, I. Keshk, H. Koch, B. Kopf, M. Kuhlmann , et al. (441 additional authors not shown)

Abstract: PANDA (anti-Proton ANnihiliation at DArmstadt) is planned to be one of the four main experiments at the future international accelerator complex FAIR (Facility for Antiproton and Ion Research) in Darmstadt, Germany. It is going to address fundamental questions of hadron physics and quantum chromodynamics using cooled antiproton beams with a high intensity and and momenta between 1.5 and 15 GeV/c.… ▽ More PANDA (anti-Proton ANnihiliation at DArmstadt) is planned to be one of the four main experiments at the future international accelerator complex FAIR (Facility for Antiproton and Ion Research) in Darmstadt, Germany. It is going to address fundamental questions of hadron physics and quantum chromodynamics using cooled antiproton beams with a high intensity and and momenta between 1.5 and 15 GeV/c. PANDA is designed to reach a maximum luminosity of 2x10^32 cm^2 s. Most of the physics programs require an excellent particle identification (PID). The PID of hadronic states at the forward endcap of the target spectrometer will be done by a fast and compact Cherenkov detector that uses the detection of internally reflected Cherenkov light (DIRC) principle. It is designed to cover the polar angle range from 5° to 22° and to provide a separation power for the separation of charged pions and kaons up to 3 standard deviations (s.d.) for particle momenta up to 4 GeV/c in order to cover the important particle phase space. This document describes the technical design and the expected performance of the novel PANDA Disc DIRC detector that has not been used in any other high energy physics experiment (HEP) before. The performance has been studied with Monte-Carlo simulations and various beam tests at DESY and CERN. The final design meets all PANDA requirements and guarantees suffcient safety margins. △ Less

Submitted 29 December, 2019; originally announced December 2019.

Comments: TDR for Panda/Fair to be published

Accurate prediction of clock transitions in a highly charged ion with complex electronic structure

Authors: C. Cheung, M. S. Safronova, S. G. Porsev, M. G. Kozlov, I. I. Tupitsyn, A. I. Bondarev

Abstract: We have developed a broadly-applicable approach that drastically increases the ability to accurately predict properties of complex atoms. We applied it to the case of Ir$^{17+}$, which is of particular interest for the development of novel atomic clocks with high sensitivity to the variation of the fine-structure constant and dark matter searches. The clock transitions are weak and very difficul… ▽ More We have developed a broadly-applicable approach that drastically increases the ability to accurately predict properties of complex atoms. We applied it to the case of Ir$^{17+}$, which is of particular interest for the development of novel atomic clocks with high sensitivity to the variation of the fine-structure constant and dark matter searches. The clock transitions are weak and very difficult to identity without accurate theoretical predictions. In the case of Ir$^{17+}$, even stronger electric-dipole (E1) transitions eluded observation despite years of effort raising the possibility that theory predictions are grossly wrong. In this work, we provide accurate predictions of transition wavelengths and E1 transition rates in Ir$^{17+}$. Our results explain the lack of observation of the E1 transitions and provide a pathway towards detection of clock transitions. Computational advances demonstrated in this work are widely applicable to most elements in the periodic table and will allow to solve numerous problems in atomic physics, astrophysics, and plasma physics. △ Less

Submitted 18 December, 2019; originally announced December 2019.

Comments: 6 pages, 3 figures

Journal ref: Phys. Rev. Lett. 124, 163001 (2020)

Fast apparent oscillations of fundamental constants

Authors: Dionysios Antypas, Dmitry Budker, Victor V. Flambaum, Mikhail G. Kozlov, Gilad Perez, Jun Ye

Abstract: Precision spectroscopy of atoms and molecules allows one to search for and to put stringent limits on the variation of fundamental constants. These experiments are typically interpreted in terms of variations of the fine structure constant $α$ and the electron to proton mass ratio $μ=m_e/m_p$. Atomic spectroscopy is usually less sensitive to other fundamental constants, unless the hyperfine struct… ▽ More Precision spectroscopy of atoms and molecules allows one to search for and to put stringent limits on the variation of fundamental constants. These experiments are typically interpreted in terms of variations of the fine structure constant $α$ and the electron to proton mass ratio $μ=m_e/m_p$. Atomic spectroscopy is usually less sensitive to other fundamental constants, unless the hyperfine structure of atomic levels is studied. However, the number of possible dimensionless constants increases when we allow for fast variations of the constants, where "fast" is determined by the time scale of the response of the studied species or experimental apparatus used. In this case, the relevant dimensionless quantity is, for example, the ratio $m_e/\langle m_e \rangle$ and $\langle m_e \rangle$ is the time average. In this sense, one may say that the experimental signal depends on the variation of dimensionful constants ($m_e$ in this example). △ Less

Submitted 14 February, 2020; v1 submitted 3 December, 2019; originally announced December 2019.

Comments: 5 pages

Journal ref: ANNALEN DER PHYSIK 2020, 1900566

High Resolution Photoexcitation Measurements Exacerbate the Long-Standing Fe XVII Oscillator Strength Problem

Authors: Steffen Kühn, Chintan Shah, José R. Crespo López-Urrutia, Keisuke Fujii, René Steinbrügge, Jakob Stierhof, Moto Togawa, Zoltán Harman, Natalia S. Oreshkina, Charles Cheung, Mikhail G. Kozlov, Sergey G. Porsev, Marianna S. Safronova, Julian C. Berengut, Michael Rosner, Matthias Bissinger, Ralf Ballhausen, Natalie Hell, SungNam Park, Moses Chung, Moritz Hoesch, Jörn Seltmann, Andrey S. Surzhykov, Vladimir A. Yerokhin, Jörn Wilms , et al. (7 additional authors not shown)

Abstract: For more than 40 years, most astrophysical observations and laboratory studies of two key soft x-ray diagnostic $2p-3d$ transitions, $3C$ and $3D$, in Fe XVII ions found oscillator strength ratios $f(3C)/f(3D)$ disagreeing with theory, but uncertainties had precluded definitive statements on this much studied conundrum. Here, we resonantly excite these lines using synchrotron radiation at PETRA II… ▽ More For more than 40 years, most astrophysical observations and laboratory studies of two key soft x-ray diagnostic $2p-3d$ transitions, $3C$ and $3D$, in Fe XVII ions found oscillator strength ratios $f(3C)/f(3D)$ disagreeing with theory, but uncertainties had precluded definitive statements on this much studied conundrum. Here, we resonantly excite these lines using synchrotron radiation at PETRA III, and reach, at a millionfold lower photon intensities, a 10 times higher spectral resolution, and 3 times smaller uncertainty than earlier work. Our final result of $f(3C)/f(3D) = 3.09(8)(6)$ supports many of the earlier clean astrophysical and laboratory observations, while departing by five sigmas from our own newest large-scale ab initio calculations, and excluding all proposed explanations, including those invoking nonlinear effects and population transfers. △ Less

Submitted 3 June, 2020; v1 submitted 21 November, 2019; originally announced November 2019.

Comments: Main text (6 pages, 3 figures), Supplmentary Material (8 pages, 4 figure), Published in Physical Review Letters

Journal ref: Phys. Rev. Lett. 124, 225001 (2020)