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Enhanced Third-Order Optical Nonlinearity in a Dipolar Carbene-Metal-Amide Material with Two-Photon Excited Delayed Fluorescence
Authors:
Ikechukwu D Nwosu,
Lujo Matasović,
Tárcius N Ramos,
Nguyen Le Phuoc,
Giacomo Londi,
Alexander J Gillett,
Daniel T W Toolan,
Charles T Smith,
George F S Whitehead,
Mireille Blanchard-Desce,
Jonathan Daniel,
Mikko Linnolahti,
Yoann Olivier,
Alexander S Romanov
Abstract:
Advanced photonic materials showing two-photon absorption (2PA) have been widely explored to develop three-dimensional imaging, micro and nanofabrication, all-optical switching, lithography on a nanoscale and many other enabling technologies. These all require nonlinear absorption chromophores with intrinsic 2PA cross-sections and long-term photo-and thermal stability. Here, we disclose the very f…
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Advanced photonic materials showing two-photon absorption (2PA) have been widely explored to develop three-dimensional imaging, micro and nanofabrication, all-optical switching, lithography on a nanoscale and many other enabling technologies. These all require nonlinear absorption chromophores with intrinsic 2PA cross-sections and long-term photo-and thermal stability. Here, we disclose the very first example of the dipolar carbenemetal-amide (CMA) material showing a enhanced 2PA cross-section up to 105 GM. Overall molecular design considerations such as extended $π$-conjugation (to increase polarizability), minimizing the singlet-triplet energy gap ($Δ$E ST ), and using heavy metal atoms are the first design principles to obtain bright one-and two-photon excited thermally activated delayed fluorescence (TADF) material, showing one of the highest radiative rate of 2.18$\bullet$10 6 s -1 across CMA materials. Bright red CMA 2P-TADF material shows excellent photostability (LT 50 = 3 h) to 20 mW femtosecond pulsed laser excitation at 1000 nm, encouraging further CMA exploration for future applications in advanced photonic technologies requiring third-order nonlinear optical properties.
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Submitted 5 March, 2026;
originally announced March 2026.
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Operational Experience of the NML Cryogenic Plant at the FAST Test Facility
Authors:
Timothy Wallace,
Joaquim Creus-Prats,
Joseph Hurd,
Michael J White,
Jerry Makara,
Liujin Pei,
Benjamin Hansen,
Jay Theilacker,
Rick Bossert,
Alexander Martinez,
James K Santucci,
Sasha Romanov
Abstract:
The NML cryogenic plant cools two individually cryostated superconducting radio frequency (SRF) capture cavities and one prototype ILC cryomodule with eight SRF cavities. This complex accelerates electrons at 150 MeV for the Integrable Optics Test Accelerator (IOTA) ring, located at the Fermilab Accelerator Science and Technology (FAST) facility. The cryogenic plant is composed of two nitrogen pre…
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The NML cryogenic plant cools two individually cryostated superconducting radio frequency (SRF) capture cavities and one prototype ILC cryomodule with eight SRF cavities. This complex accelerates electrons at 150 MeV for the Integrable Optics Test Accelerator (IOTA) ring, located at the Fermilab Accelerator Science and Technology (FAST) facility. The cryogenic plant is composed of two nitrogen precooled Tevatron satellite refrigerators, two Mycom 2016C compressors, a cryogenic distribution system, a Frick purifier compressor, two charcoal bed adsorber purifiers, and a liquid ring vacuum pump with a roots booster. The SRF cavities are immersed in a 2.0 K liquid helium bath, shielded with a 5 K gaseous helium shield and a liquid nitrogen cooled thermal shield. Since 2019, this R&D accelerator complex has gone through four science runs with an average duration of 12 months. Operational experience for each run, availability metrics, performance data and common outages are presented in this paper.
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Submitted 25 June, 2025;
originally announced June 2025.
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Spin control with triplet and doublet excitons in organic semiconductors
Authors:
Qinying Gu,
Sebastian Gorgon,
Alexander S. Romanov,
Feng Li,
Richard H. Frienda,
Emrys Evansd
Abstract:
Spin triplet exciton formation sets limits on technologies using organic semiconductors that are confined to singlet-triplet photophysics. In contrast, excitations in the spin doublet manifold in organic radical semiconductors can show efficient luminescence. Here we explore the dynamics of the spin allowed process of intermolecular energy transfer from triplet to doublet excitons. We employ a car…
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Spin triplet exciton formation sets limits on technologies using organic semiconductors that are confined to singlet-triplet photophysics. In contrast, excitations in the spin doublet manifold in organic radical semiconductors can show efficient luminescence. Here we explore the dynamics of the spin allowed process of intermolecular energy transfer from triplet to doublet excitons. We employ a carbene-metal-amide (CMA-CF3) as a model triplet donor host, since following photoexcitation it undergoes extremely fast intersystem crossing to set up a population of triplet excitons within 4 ps. This enables a foundational study for tracking energy transfer from triplets to a model radical semiconductor, TTM-3PCz. Over 90% of all radical luminescence originates from the triplet channel in this system under photoexcitation. We find that intermolecular triplet-to-doublet energy transfer can occur directly and rapidly, with 12% of triplet excitons transferring already on sub-ns timescales. This enhanced triplet harvesting mechanism is utilised in efficient near-infrared organic light-emitting diodes, which can be extended to other opto-electronic and -spintronic technologies by radical-based spin control in molecular semiconductors.
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Submitted 16 December, 2023;
originally announced December 2023.
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Reversible spin-optical interface in luminescent organic radicals
Authors:
Sebastian Gorgon,
Kuo Lv,
Jeannine Grüne,
Bluebell H. Drummond,
William K. Myers,
Giacomo Londi,
Gaetano Ricci,
Danillo Valverde,
Claire Tonnelé,
Petri Murto,
Alexander S. Romanov,
David Casanova,
Vladimir Dyakonov,
Andreas Sperlich,
David Beljonne,
Yoann Olivier,
Feng Li,
Richard H. Friend,
Emrys W. Evans
Abstract:
Molecules present a versatile platform for quantum information science, and are candidates for sensing and computation applications. Robust spin-optical interfaces are key to harnessing the quantum resources of materials. To date, carbon-based candidates have been non-luminescent, which prevents optical read-out. Here we report the first organic molecules displaying both efficient luminescence and…
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Molecules present a versatile platform for quantum information science, and are candidates for sensing and computation applications. Robust spin-optical interfaces are key to harnessing the quantum resources of materials. To date, carbon-based candidates have been non-luminescent, which prevents optical read-out. Here we report the first organic molecules displaying both efficient luminescence and near-unity generation yield of high-spin multiplicity excited states. This is achieved by designing an energy resonance between emissive doublet and triplet levels, here on covalently coupled tris(2,4,6-trichlorophenyl) methyl-carbazole radicals (TTM-1Cz) and anthracene. We observe the doublet photoexcitation delocalise onto the linked acene within a few picoseconds and subsequently evolve to a pure high spin state (quartet for monoradicals, quintet for biradical) of mixed radical-triplet character near 1.8 eV. These high-spin states are coherently addressable with microwaves even at 295 K, with optical read-out enabled by intersystem crossing to emissive states. Furthermore, for the biradical, on return to the ground state the previously uncorrelated radical spins either side of the anthracene show strong spin correlation. Our approach simultaneously supports a high efficiency of initialisation, spin manipulations and light-based read-out at room temperature. The integration of luminescence and high-spin states creates an organic materials platform for emerging quantum technologies.
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Submitted 24 March, 2023;
originally announced March 2023.
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On the energy dependence of the muon transfer rate from hydrogen to oxygen
Authors:
S. V. Romanov
Abstract:
The results of calculations of the muon transfer rate from the 1S state of muonic hydrogen to the nucleus of a free oxygen atom are presented in the interval of collision energies from 10^(-4) to 10 eV. The calculations were performed within a version of the perturbed stationary states method proposed earlier. The electron screening in the entrance channel of the transfer reaction was taken into a…
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The results of calculations of the muon transfer rate from the 1S state of muonic hydrogen to the nucleus of a free oxygen atom are presented in the interval of collision energies from 10^(-4) to 10 eV. The calculations were performed within a version of the perturbed stationary states method proposed earlier. The electron screening in the entrance channel of the transfer reaction was taken into account. A p-wave resonance in the transfer rate is predicted at collision energies of about 0.1 eV. This result is of interest in the context of the planned laser experiment on precise measurements of the hyperfine splitting energy of the 1S state of muonic hydrogen.
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Submitted 17 March, 2022;
originally announced March 2022.
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Global and local approaches to population analysis: bonding patterns in superheavy element compounds
Authors:
Alexander V. Oleynichenko,
Andréi Zaitsevskii,
Stepan Romanov,
Leonid V. Skripnikov,
Anatoly V. Titov
Abstract:
Relativistic effective atomic configurations of superheavy elements Cn, Nh and Fl and their lighter homologues (Hg, Tl and Pb) in their simple compounds with fluorine and oxygen are determined using the analysis of local properties of molecular Kohn-Sham density matrices in the vicinity of heavy nuclei. The difference in populations of atomic spinors with the same orbital angular momentum and diff…
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Relativistic effective atomic configurations of superheavy elements Cn, Nh and Fl and their lighter homologues (Hg, Tl and Pb) in their simple compounds with fluorine and oxygen are determined using the analysis of local properties of molecular Kohn-Sham density matrices in the vicinity of heavy nuclei. The difference in populations of atomic spinors with the same orbital angular momentum and different total angular momenta is demonstrated to be essential for understanding the peculiarities of chemical bonding in superheavy element compounds. The results are fully compatible with those obtained by the relativistic iterative version of conventional projection analysis of global density matrices.
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Submitted 9 December, 2021;
originally announced December 2021.
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Environmental Control of Triplet Emission in Donor-Bridge-Acceptor Organometallics
Authors:
Jiale Feng,
Lupeng Yang,
Alexander S. Romanov,
Jirawit Ratanapreechachai,
Saul T. E. Jones,
Antti-Pekka M. Reponen,
Mikko Linnolahti,
Timothy J. H. Hele,
Anna Köhler,
Heinz Bässler,
Manfred Bochmann,
Dan Credgington
Abstract:
Carbene-metal-amides (CMAs) are a promising family of donor-bridge-acceptor molecular charge-transfer emitters for organic light-emitting diodes (OLEDs). Here a universal approach is introduced to tune the energy of their charge-transfer emission. A shift of up to 210 meV is achievable in the solid state via dilution in a polar host matrix. The origin of this shift has two components: constraint o…
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Carbene-metal-amides (CMAs) are a promising family of donor-bridge-acceptor molecular charge-transfer emitters for organic light-emitting diodes (OLEDs). Here a universal approach is introduced to tune the energy of their charge-transfer emission. A shift of up to 210 meV is achievable in the solid state via dilution in a polar host matrix. The origin of this shift has two components: constraint of thermally activated triplet diffusion, and electrostatic interactions between the guest molecules and the polar host. This allows the emission of mid-green CMA archetypes to be blue shifted without chemical modifications. Monte-Carlo simulations based on a Marcus-type transfer integral successfully reproduce the concentration- and temperature-dependent triplet diffusion process, and reveal a substantial shift in the ensemble density of states in polar hosts. In gold-bridged CMAs this substantial shift does not lead to a significant change in luminescence lifetime, thermal activation energy, reorganisation energy or intersystem crossing rate. These discoveries thus offer new experimental and theoretical insight in to the coupling between the singlet and triplet manifolds in these materials. Similar emission tuning can be achieved in related materials where chemical modification is used to modify the charge-transfer energy.
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Submitted 9 August, 2019;
originally announced August 2019.
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Highly Efficient Blue Host-Free and Host-Guest Organic Light-Emitting Diodes Based on Carbene-Metal-Amides
Authors:
Patrick J. Conaghan,
Campbell S. B. Matthews,
Florian Chotard,
Saul T. E. Jones,
Neil C. Greenham,
Manfred Bochmann,
Dan Credgington,
Alexander S. Romanov
Abstract:
Carbene-metal-amide type photoemitters based on CF$_3$-substituted carbazolate ligands show sky-blue to deep-blue photoluminescence from charge-transfer excited states. They are suitable for incorporation into organic light-emitting diodes (OLEDs) by thermal vapour deposition techniques, either embedded within a high-triplet-energy host, or used host-free. We report high-efficiency OLEDs with emis…
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Carbene-metal-amide type photoemitters based on CF$_3$-substituted carbazolate ligands show sky-blue to deep-blue photoluminescence from charge-transfer excited states. They are suitable for incorporation into organic light-emitting diodes (OLEDs) by thermal vapour deposition techniques, either embedded within a high-triplet-energy host, or used host-free. We report high-efficiency OLEDs with emission ranging from yellow to blue (Commission Internationale de l'Éclairage (CIE) coordinates from [0.35, 0.53] to [0.17, 0.17]). The latter show a peak electroluminescence external quantum efficiency (EQE) of 20.9 $\%$ in a polar host. We observe that the relative energies of CT and $^{3}$LE states influence the performance of deep-blue emission from carbene-metal-amide materials. We report prototype host-free blue devices with peak external quantum efficiency of 17.3 $\%$, which maintain high performance at brightness levels of 100 cd m$^{-2}$.
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Submitted 8 August, 2019;
originally announced August 2019.
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On the muon transfer from protium to neon at low collision energies
Authors:
S. V. Romanov
Abstract:
The direct muon transfer from protium to neon at low collision energies is considered. The question is discussed how the energy dependence of the transfer rate can be extracted from available experimental data. A model is suggested which is based on two assumptions. First, the muon transfer occurs within an interaction sphere out of which the entrance and transfer channels are not coupled. Secondl…
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The direct muon transfer from protium to neon at low collision energies is considered. The question is discussed how the energy dependence of the transfer rate can be extracted from available experimental data. A model is suggested which is based on two assumptions. First, the muon transfer occurs within an interaction sphere out of which the entrance and transfer channels are not coupled. Secondly, for the s- and p-waves at low collision energies, the complex logarithmic derivatives of the radial wave functions of the entrance channel on the interaction sphere are energy-independent. With only the s-wave taken into account, two values of the logarithmic derivative were found, which agree with the transfer rates measured at the temperatures of 20 and 300 K. Within this temperature interval, the rates evaluated for these two values differ only slightly. Noticeable differences arise at temperatures of a few kelvins. The choice of the preferred value of the logarithmic derivative was made by the comparison of the energy dependence of the S-matrix with results of previous calculations. Thereby, the proposed procedure may be a way to correct calculations at low collision energies.
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Submitted 8 December, 2016;
originally announced December 2016.
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Highly efficient light-emitting diodes based on intramolecular rotation
Authors:
Dawei Di,
Alexander S. Romanov,
Le Yang,
Saul Jones,
Richard H. Friend,
Mikko Linnolahti,
Manfred Bochmann,
Dan Credgington
Abstract:
The efficiency of an organic light-emitting diode (OLED) is fundamentally governed by the spin of recombining electron-hole pairs (singlet and triplet excitons), since triplets cannot usually emit light. The singlet-triplet energy gap, a key factor for efficient utilization of triplets, is normally positive. Here we show that in a family of materials with amide donor and carbene acceptor moieties…
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The efficiency of an organic light-emitting diode (OLED) is fundamentally governed by the spin of recombining electron-hole pairs (singlet and triplet excitons), since triplets cannot usually emit light. The singlet-triplet energy gap, a key factor for efficient utilization of triplets, is normally positive. Here we show that in a family of materials with amide donor and carbene acceptor moieties linked by a metal, this energy gap for singlet and triplet excitons with charge-transfer character can be tuned from positive to negative values via the rotation of donor and acceptor about the metal-amide bond. When the gap is close to zero, facile intersystem crossing is possible, enabling efficient emission from singlet excitons. We demonstrate solution-processed LEDs with exceptionally high quantum efficiencies (near-100% internal and >27% external quantum efficiencies), and current and power efficiencies (87 cd/A and 75 lm/W) comparable to, or exceeding, those of state-of-the-art vacuum-processed OLEDs and quantum dot LEDs.
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Submitted 28 June, 2016;
originally announced June 2016.
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The calculation of the muon transfer rate from protium to neon on the ground of a two-centre Coulomb basis
Authors:
S. V. Romanov
Abstract:
Results of improved calculations of the muon transfer rate from the 1S-state of muonic protium to neon are presented in the interval of collision energies from 10^(-4) eV to 15 eV. The calculations were made within the PSS method in which the three-body wavefunction is expanded in eigenfunctions of a two- centre Coulomb problem formulated in the Jacobi coordinates of the entrance channel. This app…
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Results of improved calculations of the muon transfer rate from the 1S-state of muonic protium to neon are presented in the interval of collision energies from 10^(-4) eV to 15 eV. The calculations were made within the PSS method in which the three-body wavefunction is expanded in eigenfunctions of a two- centre Coulomb problem formulated in the Jacobi coordinates of the entrance channel. This approach provides the asymptotically correct description of this channel: the correct dissociation limit is obtained, there are no spurious long-range interactions, the polarization attraction appears naturally, the electron screening can be easily taken into account. The defects of the description are removed into the muon transfer channel in which their effect is not expected to be too significant because of large kinetic energies there. The previous calculations carried out in this way allowed one to explain experimentally observed features of the temperature dependence of the transfer rate in hydrogen-neon mixtures. In the present work, a more perfect algorithm of constructing the basis eigenfunctions has been realized and a better agreement with experimental data has been obtained.
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Submitted 19 July, 2013;
originally announced July 2013.
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Development of Nuclotron Magnet Power Supply Control System
Authors:
B. Vasilishin,
V. Andreev,
V. Gorchenko,
A. Kirichenko,
A. Kovalenko,
I. Kulikov,
B. Omelchenko,
V. Karpinsky,
S. Romanov,
B. Sveshnikov,
A. Tharenkov,
V. Volkov
Abstract:
The magnetic field control subsystem of the Nuclotron - a superferric ion synchrotron - is described. The bending (BM), focusing (QF) and defocusing (QD) magnets are powered by three supplies. The BMs are driven by the supply of a 6.3 kA nominal current. The QFs and QDs are connected in series and powered by the 6 kA supply. An additional supply of 200 A for the QFs is used to keep the reqired r…
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The magnetic field control subsystem of the Nuclotron - a superferric ion synchrotron - is described. The bending (BM), focusing (QF) and defocusing (QD) magnets are powered by three supplies. The BMs are driven by the supply of a 6.3 kA nominal current. The QFs and QDs are connected in series and powered by the 6 kA supply. An additional supply of 200 A for the QFs is used to keep the reqired ratio I(QF)/I(QD). The BM magnetic field shape is set by a pulse function generator which produceds a reference burst (Bo-train) with a 0.1 Gs resolution. A real B-train of the bending magnet field with the same (0.1 Gs) resolution is used for feedback loop and as reference function for QD and QF supplies. The QD and QF trains are utilized for feedback loop in the QD and QF supplies. The control of slow extraction system suppllies is described as well.
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Submitted 22 October, 2001;
originally announced October 2001.