Showing 1–16 of 16 results for author: Pang, D Y

Observation of Tensor-Driven High-Momentum Neutrons in ${}^{16}$O via ($p,d$) Reactions and Zero-Degree Deuteron Momentum Spectroscopy

Authors: X. Wang, H. J. Ong, S. Terashima, I. Tanihata, Y. K. Tanaka, N. Aoi, Y. Ayyad, J. Benlliure, F. Farinon, H. Fujioka, H. Geissel, J. Gellanki, C. L. Guo, E. Haettner, W. L. Hai, M. N. Harakeh, C. Hornung, K. Itahashi, R. Janik, N. Kalantar-Nayestanaki, R. Knobel, N. Kurz, K. Miki, I. Mukha, T. Myo , et al. (20 additional authors not shown)

Abstract: The $^{16}\mathrm{O}(p,d)^{15}\mathrm{O}$ reaction has been studied at $0^{\circ}$ using 403-, 604-, 907- and 1209-MeV protons, comparing cross sections populating positive- and negative-parity states in $^{15}\mathrm{O}$. Transitions to positive-parity states exhibit strong sensitivity to high-momentum neutrons, while negative-parity transitions show much smaller effects. The cross-section ratio… ▽ More The $^{16}\mathrm{O}(p,d)^{15}\mathrm{O}$ reaction has been studied at $0^{\circ}$ using 403-, 604-, 907- and 1209-MeV protons, comparing cross sections populating positive- and negative-parity states in $^{15}\mathrm{O}$. Transitions to positive-parity states exhibit strong sensitivity to high-momentum neutrons, while negative-parity transitions show much smaller effects. The cross-section ratio between positive- and negative-parity states rises sharply with momentum transfer, matching theoretical predictions that include tensor interactions, particularly the peak near $2~\mathrm{fm}^{-1}$ for the $5/2^{+}$ to ground-state ratio. These results highlight $0^{\circ}$ neutron-pickup reactions as a sensitive probe for tensor-driven high-momentum components, paving the way for studies in exotic nuclei via radioactive beams. △ Less

Submitted 19 August, 2025; v1 submitted 17 August, 2025; originally announced August 2025.

Observation of the near-threshold intruder $0^-$ resonance in $^{12}$Be

Authors: J. Chen, S. M. Wang, H. T. Fortune, J. L. Lou, Y. L. Ye, Z. H. Li, N. Michel, J. G. Li, C. X. Yuan, Y. C. Ge, Q. T. Li, H. Hua, D. X. Jiang, X. F. Yang, D. Y. Pang, F. R. Xu, W. Zuo, J. C. Pei, J. Li, W. Jiang, Y. L. Sun, H. L. Zang, N. Aoi, H. J. Ong, E. Ideguchi , et al. (12 additional authors not shown)

Abstract: A resonant state at $3.21^{+0.12}_{-0.04}$\,MeV, located just above the one-neutron separation threshold, was observed for the first time in $^{12}$Be from the $^{11}$Be\,$(d,p)^{12}$Be one-neutron transfer reaction in inverse kinematics. This state is assigned a spin-parity of $0^-$, according to the distorted-wave Born approximation (DWBA) and decay-width analysis. Gamow coupled-channel (GCC) an… ▽ More A resonant state at $3.21^{+0.12}_{-0.04}$\,MeV, located just above the one-neutron separation threshold, was observed for the first time in $^{12}$Be from the $^{11}$Be\,$(d,p)^{12}$Be one-neutron transfer reaction in inverse kinematics. This state is assigned a spin-parity of $0^-$, according to the distorted-wave Born approximation (DWBA) and decay-width analysis. Gamow coupled-channel (GCC) and Gamow shell-model (GSM) calculations show the importance of the continuum-coupling, which dramatically influences the excitation energy and ordering of low-lying states. Various exotic structures associated with cross-shell intruding configurations in $^{12}$Be and in its isotonic nucleus $^{11}$Li are comparably discussed. △ Less

Submitted 3 March, 2021; originally announced March 2021.

Study of $s$- and $d$-wave intruder strengths in $^{13}{\rm B}_{\rm g.s.}$ via a $p(^{13}{\rm B},d)^{12}{\rm B}$ reaction

Authors: W. Liu, J. L. Lou, Y. L. Ye, Z. H. Li, Q. T. Li, H. Hua, X. F. Yang, J. Y. Xu, H. J. Ong, D. T. Tran, N. Aoi, E. Ideguchi, D. Y. Pang, C. X. Yuan, S. M. Wang, Y. Jiang, B. Yang, Y. Liu, J. G. Li, Z. Q. Chen, J. X. Han, S. W. Bai, G. Li, K. Ma, Z. W. Tan , et al. (2 additional authors not shown)

Abstract: Experimental results of the $p(^{13}{\rm B},d)^{12}{\rm B}$ transfer reaction to the low-lying states in $^{12}$B are reported. The optical potential parameters for the entrance channel are extracted from the elastic scattering $p$($^{13}{\rm B}$, $p$) measured in the same experiment, while those for the exit channel are global ones. Spectroscopic factors associated with the $p$-, $s$-, and $d$-wa… ▽ More Experimental results of the $p(^{13}{\rm B},d)^{12}{\rm B}$ transfer reaction to the low-lying states in $^{12}$B are reported. The optical potential parameters for the entrance channel are extracted from the elastic scattering $p$($^{13}{\rm B}$, $p$) measured in the same experiment, while those for the exit channel are global ones. Spectroscopic factors associated with the $p$-, $s$-, and $d$-wave neutron transfer to the known $^{12}$B states, are extracted by comparing the deuteron angular distributions with the calculation results. The separated $s$- and $d$-wave intruder strengths in $^{13}{\rm B}_{\rm g.s.}$ were determined to be $10(2)\%$ and $6(1)\%$, respectively, which follow roughly the systematics for the $N$ = 8 neutron-rich isotones. The measured total intruder strength is in good agreement with the shell model calculation, while the individual ones evolve quite differently. Particularly, the sudden change of the $d$-wave intensity between $^{13}$B and $^{12}$Be needs further theoretical interpretation. △ Less

Submitted 2 March, 2021; originally announced March 2021.

Comments: 8 pages,8 figures

Determination of the cluster-decay branching ratio from a near-threshold molecular state in $^{10}$Be

Authors: W. Jiang, Y. L. Ye, C. J. Lin, Z. H. Li, J. L. Lou, X. F. Yang, Q. T. Li, Y. C. Ge, H. Hua, D. X. Jiang, D. Y. Pang, J. Li, J. Chen, Z. H. Yang, X. H. Sun, Z. Y. Tian, J. Feng, B. Yang, H. L. Zang, Q. Liu, P. J. Li, Z. Q. Chen, Y. Liu, Y. Zhang, J. Ma , et al. (5 additional authors not shown)

Abstract: A puzzle has long existed for the $α$-cluster content in the near-threshold 7.54 MeV state of $^{10}$Be. A new measurement was conducted to measure the cluster-decay partial width of this state, using the reaction $\rm{^9Be}(\rm{^9Be}, \rm{^{10}Be}^{*} \rightarrow α+ \rm{^6He})\rm{^8Be}$ at 45 MeV beam energy. Special measures were taken to reduce the strong near-threshold background. The neutron-… ▽ More A puzzle has long existed for the $α$-cluster content in the near-threshold 7.54 MeV state of $^{10}$Be. A new measurement was conducted to measure the cluster-decay partial width of this state, using the reaction $\rm{^9Be}(\rm{^9Be}, \rm{^{10}Be}^{*} \rightarrow α+ \rm{^6He})\rm{^8Be}$ at 45 MeV beam energy. Special measures were taken to reduce the strong near-threshold background. The neutron-decay strength was also obtained based on the three-fold coincident measurement. A cluster-decay branching ratio of $(4.04 \pm 1.26)\times 10^{-4}$ is obtained, resulting in a reasonably large $α$-cluster spectroscopic factor. The present work confirms the formation of the $σ$-bond molecular rotational band headed by the 6.18 MeV state in $^{10}$Be. △ Less

Submitted 5 March, 2020; originally announced March 2020.

Astrophysical $S_{E2}$ factor of the ${}^{12}\mathrm{C}(α,γ){}^{16}\mathrm{O}$ reaction through the ${}^{12}\mathrm{C}({}^{11}\mathrm{B},{}^{7}\mathrm{Li}){}^{16}\mathrm{O}$ transfer reaction

Authors: Y. P. Shen, B. Guo, Z. H. Li, Y. J. Li, D. Y. Pang, S. Adhikari, Z. D. An, J. Su, S. Q. Yan, X. C. Du, Q. W. Fan, L. Gan, Z. Y. Han, D. H. Li, E. T. Li, G. Lian, J. C. Liu, T. L. Ma, C. J. Pei, Y. Su, Y. B. Wang, Y. Zhou, W. P. Liu

Abstract: The ${}^{12}\mathrm{C}(α,γ){}^{16}\mathrm{O}$ reaction plays a key role in the evolution of stars with masses of $M >$ 0.55 $M_\odot$. The cross-section of the ${}^{12}\mathrm{C}(α,γ){}^{16}\mathrm{O}$ reaction within the Gamow window ($E_\textrm{c.m.}$ = 300 keV, $T_\textrm9$ = 0.2) is extremely small (about $10^{-17}$ barn), which makes the direct measurement in a ground-based laboratory with ex… ▽ More The ${}^{12}\mathrm{C}(α,γ){}^{16}\mathrm{O}$ reaction plays a key role in the evolution of stars with masses of $M >$ 0.55 $M_\odot$. The cross-section of the ${}^{12}\mathrm{C}(α,γ){}^{16}\mathrm{O}$ reaction within the Gamow window ($E_\textrm{c.m.}$ = 300 keV, $T_\textrm9$ = 0.2) is extremely small (about $10^{-17}$ barn), which makes the direct measurement in a ground-based laboratory with existing techniques unfeasible. Up until now, the cross-sections at lower energies can only be extrapolated from the data at higher energies. However, two subthreshold resonances, located at $E_x$ = 7.117 MeV and $E_x$ = 6.917 MeV, make this extrapolation more complicated. In this work, the 6.917 MeV subthreshold resonance in the ${}^{12}\mathrm{C}(α,γ){}^{16}\mathrm{O}$ reaction was investigated via the ${}^{12}\mathrm{C}({}^{11}\mathrm{B},{}^{7}\mathrm{Li}){}^{16}\mathrm{O}$ reaction. The experiment was performed using the Q3D magnetic spectrograph at the HI-13 tandem accelerator. We measured the angular distribution of the ${}^{12}\mathrm{C}({}^{11}\mathrm{B},{}^{7}\mathrm{Li}){}^{16}\mathrm{O}$ transfer reaction leading to the 6.917 MeV state. Based on the FRDWBA analysis, we derived the asymptotic normalization coefficient (ANC) of the 6.917 MeV level in $^{16}$O to be (1.10 $\pm$ 0.29) $\times 10^{10}$ fm$^{-1}$, with which the reduced $α$ width was computed to be $18.0\pm4.7$ keV at the channel radius of 6.5 fm. Finally, we calculated the astrophysical $S_{E2}(300)$ factor of the ground-state transitions to be 46.2 $\pm$ 7.7 keV b. The result for the astrophysical $S_{E2}(300)$ factor confirms the values obtained in various direct and indirect measurements and presents an independent examination of the most important data in nuclear astrophysics. △ Less

Submitted 15 November, 2018; originally announced November 2018.

Comments: submitted to Physical Review C

Journal ref: Phys. Rev. C 99, 025805 (2019)

Binding-energy independence of reduced single particle strengths derived from $(p,d)$ reactions

Authors: Y. P. Xu, D. Y. Pang, X. Y. Yun, C. Wen, C. X. Yuan, J. L. Lou

Abstract: An overall reduction factor (ORF) is introduced for studying the quenching of single particle strengths through nucleon transfer reactions. The ORF includes contributions of all the probed bound states of the residual nucleus in a transfer reaction and permits a proper comparison with results of inclusive knockout reactions. A systematic analysis is made with 103 sets of angular distribution data… ▽ More An overall reduction factor (ORF) is introduced for studying the quenching of single particle strengths through nucleon transfer reactions. The ORF includes contributions of all the probed bound states of the residual nucleus in a transfer reaction and permits a proper comparison with results of inclusive knockout reactions. A systematic analysis is made with 103 sets of angular distribution data of $(p,d)$ reactions on 21 even-even targets with atomic mass numbers from 8 to 56 using the consistent three-body model reaction methodology proposed in [J. Lee, J.A. Tostevin, B.A. Brown, et al., Phys. Rev. C 73, 044608 (2006)]. The extracted ORFs are found to be nearly independent on the nuclear isospin asymmetry, which is different from the systematics of inclusive knockout reactions but is consistent with the recent measurement of $(d,t)$, $(d,3He)$, $(p,2p)$, and $(p,pn)$ reactions on nitrogen and oxygen isotopes and \textit{ab initio} calculations. △ Less

Submitted 3 October, 2018; v1 submitted 28 September, 2018; originally announced September 2018.

Comments: 15 pages, 3 figures

A New Measurement of the Intruder Configuration in 12Be

Authors: J. Chen, J. L. Lou, Y. L. Ye, Z. H. Li, D. Y. Pang, C. X. Yuan, Y. C. Ge, Q. T. Li, H. Hua, D. X. Jiang, X. F. Yang, F. R. Xu, J. C. Pei, J. Li, W. Jiang, Y. L. Sun, H. L. Zang, Y. Zhang, N. Aoi, E. Ideguchi, H. J. Ong, J. Lee, J. Wu, H. N. Liu, C. Wen , et al. (6 additional authors not shown)

Abstract: A new $^{11}$Be($d,p$)$^{12}$Be transfer reaction experiment was carried out in inverse kinematics at 26.9$A$ MeV, with special efforts devoted to the determination of the deuteron target thickness and of the required optical potentials from the present elastic scattering data. In addition, a direct measurement of the cross sections for the 0$_2^+$ state was realized by applying an isomer-tagging… ▽ More A new $^{11}$Be($d,p$)$^{12}$Be transfer reaction experiment was carried out in inverse kinematics at 26.9$A$ MeV, with special efforts devoted to the determination of the deuteron target thickness and of the required optical potentials from the present elastic scattering data. In addition, a direct measurement of the cross sections for the 0$_2^+$ state was realized by applying an isomer-tagging technique. The s-wave spectroscopic factors of 0.20(0.04) and 0.41(0.11) were extracted for the 0$_1^+$ and 0$_2^+$ states, respectively, in $^{12}$Be. Using the ratio of these spectroscopic factors, together with the previously reported results for the p-wave components, the single-particle component intensities in the bound 0$^+$ states of $^{12}$Be were deduced, allowing a direct comparison with the theoretical predictions. It is evidenced that the ground-state configuration of $^{12}$Be is dominated by the d-wave intruder, exhibiting a dramatic evolution of the intruding mechanism from $^{11}$Be to $^{12}$Be, with a persistence of the $N = 8$ magic number broken. △ Less

Submitted 15 May, 2018; originally announced May 2018.

Journal ref: Physics Letters B 781, 412 (2018)

Optical model potential of deuteron with $1p$-shell nuclei

Authors: Y. Zhang, D. Y. Pang, J. L. Lou

Abstract: A set of global optical potential parameters, DA1p, for deuterons with the $1p$-shell nuclei is obtained by simultaneously fitting 67 sets of experimental data of deuteron elastic scattering from \nuc{6}{Li}, \nuc{9}{Be}, \nuc{10}{B}, \nuc{11}{B}, \nuc{12}{C}, \nuc{13}{C}, \nuc{14}{N}, \nuc{16}{O} and \nuc{18}{O} with incident energies between 5.25 and 170 MeV. DA1p improves the description of the… ▽ More A set of global optical potential parameters, DA1p, for deuterons with the $1p$-shell nuclei is obtained by simultaneously fitting 67 sets of experimental data of deuteron elastic scattering from \nuc{6}{Li}, \nuc{9}{Be}, \nuc{10}{B}, \nuc{11}{B}, \nuc{12}{C}, \nuc{13}{C}, \nuc{14}{N}, \nuc{16}{O} and \nuc{18}{O} with incident energies between 5.25 and 170 MeV. DA1p improves the description of the deuteron elastic scattering from the $1p$-shell nuclei with respect to the existing systematic deuteron potentials and can give satisfactory reproduction to the experimental data with radiative nuclei such as \nuc{9}{Li}, \nuc{10}{Be}, \nuc{14}{C} and \nuc{14}{O}. △ Less

Submitted 5 June, 2016; originally announced June 2016.

Surface-integral formalism of deuteron stripping

Authors: A. M. Mukhamedzhanov, D. Y. Pang, C. A. Bertulani, A. S. Kadyrov

Abstract: The purpose of this paper is to develop an alternative theory of deuteron stripping to resonance states based on the surface integral formalism of Kadyrov et al. [Ann. Phys. 324, 1516 (2009)] and continuum-discretized coupled channels (CDCC). First we demonstrate how the surface integral formalism works in the three-body model and then we consider a more realistic problem in which a composite st… ▽ More The purpose of this paper is to develop an alternative theory of deuteron stripping to resonance states based on the surface integral formalism of Kadyrov et al. [Ann. Phys. 324, 1516 (2009)] and continuum-discretized coupled channels (CDCC). First we demonstrate how the surface integral formalism works in the three-body model and then we consider a more realistic problem in which a composite structure of target nuclei is taken via optical potentials. We explore different choices of channel wave functions and transition operators and show that a conventional CDCC volume matrix element can be written in terms of a surface-integral matrix element, which is peripheral, and an auxiliary matrix element, which determines the contribution of the nuclear interior over the variable $r_{nA}$. This auxiliary matrix element appears due to the inconsistency in treating of the $n-A$ potential: this potential should be real in the final state to support bound states or resonance scattering and complex in the initial state to describe $n-A$ scattering. Our main result is formulation of the theory of the stripping to resonance states using the prior form of the surface integral formalism and CDCC method. It is demonstrated that the conventional CDCC volume matrix element coincides with the surface matrix element, which converges for the stripping to the resonance state. Also the surface representation (over the variable $r_{nA}$ of the stripping matrix element enhances the peripheral part of the amplitude although the internal contribution doesn't disappear and increases with increase of the deuteron energy. We present calculations corroborating our findings for both stripping to the bound state and the resonance. △ Less

Submitted 24 August, 2014; originally announced August 2014.

Comments: 54 pages, 12 figures, accepted for publication in the Physical Review C

Proton widths of the low-lying 16F states from the 15N(7Li, 6Li)16N reaction

Authors: Z. D. Wu, B. Guo, Z. H. Li, Y. J. Li, J. Su, D. Y. Pang, S. Q. Yan, E. T. Li, X. X. Bai, X. C. Du, Q. W. Fan, L. Gan, J. J. He, S. J. Jin, L. Jing, L. Li, Z. C. Li, G. Lian, J. C. Liu, Y. P. Shen, Y. B. Wang, X. Q. Yu, S. Zeng, D. H. Zhang, L. Y. Zhang , et al. (2 additional authors not shown)

Abstract: All the 16F levels are unbound by proton emission. To date the four low-lying 16F levels below 1 MeV have been experimentally identified with well established spin-parity values and excitation energies with an accuracy of 4 - 6 keV. However, there are still considerable discrepancies for their level widths. The present work aims to explore these level widths through an independent method. The angu… ▽ More All the 16F levels are unbound by proton emission. To date the four low-lying 16F levels below 1 MeV have been experimentally identified with well established spin-parity values and excitation energies with an accuracy of 4 - 6 keV. However, there are still considerable discrepancies for their level widths. The present work aims to explore these level widths through an independent method. The angular distributions of the 15N(7Li, 6Li)16N reaction leading to the first four states in 16N were measured using a high-precision Q3D magnetic spectrograph. The neutron spectroscopic factors and the asymptotic normalization coefficients for these states in 16N were then derived based on distorted wave Born approximation analysis. The proton widths of the four low-lying resonant states in 16F were obtained according to charge symmetry of strong interaction. △ Less

Submitted 27 March, 2014; originally announced March 2014.

Comments: 14 pages, 6 figures, 4 tables

Spectroscopic factors for low-lying 16N levels and the astrophysical 15N(n,gamma)16N reaction rate

Authors: B. Guo, Z. H. Li, Y. J. Li, J. Su, D. Y. Pang, S. Q. Yan, Z. D. Wu, E. T. Li, X. X. Bai, X. C. Du, Q. W. Fan, L. Gan, J. J. He, S. J. Jin, L. Jing, L. Li, Z. C. Li, G. Lian, J. C. Liu, Y. P. Shen, Y. B. Wang, X. Q. Yu, S. Zeng, L. Y. Zhang, W. J. Zhang , et al. (1 additional authors not shown)

Abstract: Fluorine is a key element for nucleosynthetic studies since it is extremely sensitive to the physical conditions within stars. The astrophysical site to produce fluorine is suggested to be asymptotic giant branch (AGB) stars. In these stars the 15N(n, g)16N reaction could affect the abundance of fluorine by competing with 15N(a, g)19F. The 15N(n, g)16N reaction rate depends directly on the neutron… ▽ More Fluorine is a key element for nucleosynthetic studies since it is extremely sensitive to the physical conditions within stars. The astrophysical site to produce fluorine is suggested to be asymptotic giant branch (AGB) stars. In these stars the 15N(n, g)16N reaction could affect the abundance of fluorine by competing with 15N(a, g)19F. The 15N(n, g)16N reaction rate depends directly on the neutron spectroscopic factors of the low-lying states in 16N. The angular distributions of the 15N(7Li, 6Li)16N reaction populating the ground state and the first three excited states in 16N are measured using a Q3D magnetic spectrograph and are used to derive the spectroscopic factors of these states based on distorted wave Born approximation (DWBA) analysis. The spectroscopic factors of these four states are extracted to be 0.96+-0.09, 0.69+-0.09, 0.84+-0.08 and 0.65+-0.08, respectively. Based on the new spectroscopic factors we derive the 15N(n,g)16N reaction rate. The accuracy and precision of the spectroscopic factors are enhanced due to the first application of high-precision magnetic spectrograph for resolving the closely-spaced 16N levels which can not be achieved in most recent measurement. The present result demonstrates that two levels corresponding to neutron transfers to the 2s1/2 orbit in 16N are not so good single-particle levels although 15N is a closed neutron-shell nucleus. This finding is contrary to the shell model expectation. The present work also provides an independent examination to shed some light on the existing discrepancies in the spectroscopic factors and the 15N(n, g)16N rate. △ Less

Submitted 30 December, 2013; originally announced January 2014.

Comments: 13 pages, 4 figures, 2 tables

Journal ref: Phys. Rev. C 89, 012801(R) (2014)

Rapid convergence of the Weinberg expansion of the deuteron stripping amplitude

Authors: D. Y. Pang, N. K. Timofeyuk, R. C. Johnson, J. A. Tostevin

Abstract: Theories of $(d,p)$ reactions frequently use a formalism based on a transition amplitude that is dominated by the components of the total three-body scattering wave function where the spatial separation between the incoming neutron and proton is confined by the range of the $n$-$p$ interaction, $V_{np}$. By comparison with calculations based on the CDCC method we show that the $(d,p)$ transition a… ▽ More Theories of $(d,p)$ reactions frequently use a formalism based on a transition amplitude that is dominated by the components of the total three-body scattering wave function where the spatial separation between the incoming neutron and proton is confined by the range of the $n$-$p$ interaction, $V_{np}$. By comparison with calculations based on the CDCC method we show that the $(d,p)$ transition amplitude is dominated by the first term of the expansion of the three-body wave function in a complete set of Weinberg states. We use the \nuc{132}{Sn}(d,p)\nuc{133} {Sn} reaction at 30 and 100 MeV as examples of contemporary interest. The generality of this observed dominance and its implications for future theoretical developments are discussed. △ Less

Submitted 19 June, 2013; v1 submitted 11 June, 2013; originally announced June 2013.

Comments: 6 pages, 4 figures, Physical Review C - Accepted

New determination of the 13C(a, n)16O reaction rate and its influence on the s-process nucleosynthesis in AGB stars

Authors: B. Guo, Z. H. Li, M. Lugaro, J. Buntain, D. Y. Pang, Y. J. Li, J. Su, S. Q. Yan, X. X. Bai, Y. S. Chen, Q. W. Fan, S. J. Jin, A. I. Karakas, E. T. Li, Z. C. Li, G. Lian, J. C. Liu, X. Liu, J. R. Shi, N. C. Shu, B. X. Wang, Y. B. Wang, S. Zeng, W. P. Liu

Abstract: We present a new measurement of the $α$-spectroscopic factor ($S_α$) and the asymptotic normalization coefficient (ANC) for the 6.356 MeV 1/2$^+$ subthreshold state of $^{17}$O through the $^{13}$C($^{11}$B, $^{7}$Li)$^{17}$O transfer reaction and we determine the $α$-width of this state. This is believed to have a strong effect on the rate of the $^{13}$C($α$, $n$)$^{16}$O reaction, the main neut… ▽ More We present a new measurement of the $α$-spectroscopic factor ($S_α$) and the asymptotic normalization coefficient (ANC) for the 6.356 MeV 1/2$^+$ subthreshold state of $^{17}$O through the $^{13}$C($^{11}$B, $^{7}$Li)$^{17}$O transfer reaction and we determine the $α$-width of this state. This is believed to have a strong effect on the rate of the $^{13}$C($α$, $n$)$^{16}$O reaction, the main neutron source for {\it slow} neutron captures (the $s$-process) in asymptotic giant branch (AGB) stars. Based on the new width we derive the astrophysical S-factor and the stellar rate of the $^{13}$C($α$, $n$)$^{16}$O reaction. At a temperature of 100 MK our rate is roughly two times larger than that by \citet{cau88} and two times smaller than that recommended by the NACRE compilation. We use the new rate and different rates available in the literature as input in simulations of AGB stars to study their influence on the abundances of selected $s$-process elements and isotopic ratios. There are no changes in the final results using the different rates for the $^{13}$C($α$, $n$)$^{16}$O reaction when the $^{13}$C burns completely in radiative conditions. When the $^{13}$C burns in convective conditions, as in stars of initial mass lower than $\sim$2 $M_\sun$ and in post-AGB stars, some changes are to be expected, e.g., of up to 25% for Pb in our models. These variations will have to be carefully analyzed when more accurate stellar mixing models and more precise observational constraints are available. △ Less

Submitted 3 August, 2012; originally announced August 2012.

Journal ref: Astrophys. J. 756, 193, 2012

Possible evidence of tensor interactions in 16O observed via (p,d) reaction

Authors: H. J. Ong, I. Tanihata, A. Tamii, T. Myo, K. Ogata, M. Fukuda, K. Hirota, K. Ikeda, D. Ishikawa, T. Kawabata, H. Matsubara, K. Matsuta, M. Mihara, T. Naito, D. Nishimura, Y. Ogawa, H. Okamura, A. Ozawa, D. Y. Pang, H. Sakaguchi, K. Sekiguchi, T. Suzuki, M. Taniguchi, M. Takashina, H. Toki , et al. (3 additional authors not shown)

Abstract: We have measured 16O(p,d) reaction using 198-, 295- and 392-MeV proton beams to search for a direct evidence on the effect of the tensor interactions in light nucleus. Differential cross sections of the one-neutron transfer reactions populating the ground states and several low-lying excited states in 15O were measured. Comparing the ratios of the cross sections for each excited state to the one f… ▽ More We have measured 16O(p,d) reaction using 198-, 295- and 392-MeV proton beams to search for a direct evidence on the effect of the tensor interactions in light nucleus. Differential cross sections of the one-neutron transfer reactions populating the ground states and several low-lying excited states in 15O were measured. Comparing the ratios of the cross sections for each excited state to the one for the ground state over a wide range of momentum transfer, we found a marked enhancement for the positive-parity state(s). The observation indicates large components of high-momentum neutrons in the initial ground-state configurations, due possibly to the tensor interactions. △ Less

Submitted 19 May, 2012; originally announced May 2012.

Comments: 11 pages, 2 figures

Spectroscopy of $^{18}$Na: Bridging the two-proton radioactivity of $^{19}$Mg

Authors: M. Assié, F. de Oliveira Santos, T. Davinson, F. de Grancey, L. Achouri, J. Alcántara-Núñez, T. Al Kalanee, J. -C. Angélique, C. Borcea, R. Borcea, L. Caceres, I. Celikovic, V. Chudoba, D. Y. Pang, C. Ducoin, M. Fallot, O. Kamalou, J. Kiener, Y. Lam, A. Lefebvre-Schuhl, G. Lotay, J. Mrazek, L. Perrot, A. M. Sánchez-Benítez, F. Rotaru , et al. (9 additional authors not shown)

Abstract: The unbound nucleus $^{18}$Na, the intermediate nucleus in the two-proton radioactivity of $^{19}$Mg, was studied by the measurement of the resonant elastic scattering reaction $^{17}$Ne(p,$^{17}$Ne)p performed at 4 A.MeV. Spectroscopic properties of the low-lying states were obtained in a R-matrix analysis of the excitation function. Using these new results, we show that the lifetime of the… ▽ More The unbound nucleus $^{18}$Na, the intermediate nucleus in the two-proton radioactivity of $^{19}$Mg, was studied by the measurement of the resonant elastic scattering reaction $^{17}$Ne(p,$^{17}$Ne)p performed at 4 A.MeV. Spectroscopic properties of the low-lying states were obtained in a R-matrix analysis of the excitation function. Using these new results, we show that the lifetime of the $^{19}$Mg radioactivity can be understood assuming a sequential emission of two protons via low energy tails of $^{18}$Na resonances. △ Less

Submitted 6 October, 2011; originally announced October 2011.

The $^{8}$He and $^{10}$He spectra studied in the $(t$,$p)$ reaction

Authors: M. S. Golovkov, L. V. Grigorenko, G. M. Ter-Akopian, A. S. Fomichev, Yu. Ts. Oganessian, V. A. Gorshkov, S. A. Krupko, A. M. Rodin, S. I. Sidorchuk, R. S. Slepnev, S. V. Stepantsov, R. Wolski, D. Y. Pang, V. Chudoba, A. A. Korsheninnikov, E. A. Kuzmin, E. Yu. Nikolskii, B. G. Novatskii, D. N. Stepanov, P. Roussel-Chomaz, W. Mittig, A. Ninane, F. Hanappe, L. Stuttge, A. A. Yukhimchuk , et al. (4 additional authors not shown)

Abstract: The low-lying spectra of $^8$He and $^{10}$He nuclei were studied in the $^3$H($^6$He,$p$)$^8$He and $^3$H($^8$He,$p$)$^{10}$He transfer reactions. The $0^+$ ground state (g.s.) of $^8$He and excited states, $2^+$ at $3.6-3.9$ MeV and $(1^+)$ at $5.3-5.5$ MeV, were populated with cross sections of 200, 100-250, and 90-125 $μ$b/sr, respectively. Some evidence for $^8$He state at about 7.5 MeV is… ▽ More The low-lying spectra of $^8$He and $^{10}$He nuclei were studied in the $^3$H($^6$He,$p$)$^8$He and $^3$H($^8$He,$p$)$^{10}$He transfer reactions. The $0^+$ ground state (g.s.) of $^8$He and excited states, $2^+$ at $3.6-3.9$ MeV and $(1^+)$ at $5.3-5.5$ MeV, were populated with cross sections of 200, 100-250, and 90-125 $μ$b/sr, respectively. Some evidence for $^8$He state at about 7.5 MeV is obtained. We discuss a possible nature of the near-threshold anomaly above 2.14 MeV in $^8$He and relate it to the population of a $1^-$ continuum (soft dipole excitation) with peak value at about 3 MeV. The lowest energy group of events in the $^{10}$He spectrum was observed at $\sim 3$ MeV with a cross section of $\sim 140$ $μ$b/sr. We argue that this result is possibly consistent with the previously reported observation of $^{10}$He, in that case providing a new g.s. position for $^{10}$He at about 3 MeV. △ Less

Submitted 2 April, 2008; originally announced April 2008.

Comments: 18 pages, 8 figures, submitted to Phys. Lett. B

Journal ref: Phys.Lett.B672:22-29,2009