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A high-lying isomer in ^{92}Zr with lifetime modulated by the atomic charge states: a proposed approach for a nuclear gamma-ray laser
Authors:
C. X. Jia,
S. Guo,
B. Ding,
X. H. Zhou,
C. X. Yuan,
W. Hua J. G. Wang,
S. W. Xu,
C. M. Petrache,
E. A. Lawrie,
Y. B. Wu,
Y. D. Fang,
Y. H. Qiang,
Y. Y. Yang,
J. B. Ma,
J. L. Chen,
H. X. Chen,
F. Fang,
Y. H. Yu,
B. F. Lv,
F. F. Zeng,
Q. B. Zeng,
H. Huang,
Z. H. Jia,
W. Liang,
W. Q. Zhang
, et al. (23 additional authors not shown)
Abstract:
The nuclides ^{92}Zr are produced and transported by using a radioactive beam line to a lowbackground detection station. After a flight time of about 1.14 μs, the ions are implanted into a carbon foil, and four γ rays deexciting the 8+ state in ^{92}Zr are observed in coincidence with the implantation signals within a few nanoseconds. We conjecture that there exists an isomer located slightly abov…
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The nuclides ^{92}Zr are produced and transported by using a radioactive beam line to a lowbackground detection station. After a flight time of about 1.14 μs, the ions are implanted into a carbon foil, and four γ rays deexciting the 8+ state in ^{92}Zr are observed in coincidence with the implantation signals within a few nanoseconds. We conjecture that there exists an isomer located slightly above the 8^{+} state in ^{92}Zr. The isomeric lifetime in highly charged states is extended significantly due to the blocking of internal conversion decay channels, enabling its survival over the transportation. During the slowing-down process in the carbon foil, the ^{92}Zr ions capture electron and evolve toward neutral atoms, and consequently the lifetime is restored to a normal short value. Such a high-lying isomer depopulated by a low-energy transition may provide unique opportunity to develop nuclear γ laser.
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Submitted 3 September, 2025;
originally announced September 2025.
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$t$+$t$ cluster states in $^{6}$He
Authors:
W. H. Ma,
D. Y. Tao,
B. Zhou,
J. S. Wang,
Y. G. Ma,
D. Q. Fang,
W. B. He,
Y. Y. Yang,
J. B. Ma,
S. L. Jin,
P. Ma,
J. X. Li,
Y. S. Song,
Q. Hu,
Z. Bai,
M. R. Huang,
X. Q. Liu,
Z. H. Gao,
F. F. Duan,
S. Y. Jin,
S. W. Xu,
G. M. Yu,
T. F. Wang,
Q. Wang
Abstract:
The study of $t$+$t$ cluster states in $^{6}$He provides valuable insights into exotic nuclear structures and the behavior of fermionic cluster systems. This study shows rich cluster resonant state structures above the threshold, identified by experimental reconstruction and theoretical calculations. The excitation energy spectrum above the $t$+$t$ threshold in $^{6}$He is measured via the fragmen…
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The study of $t$+$t$ cluster states in $^{6}$He provides valuable insights into exotic nuclear structures and the behavior of fermionic cluster systems. This study shows rich cluster resonant state structures above the threshold, identified by experimental reconstruction and theoretical calculations. The excitation energy spectrum above the $t$+$t$ threshold in $^{6}$He is measured via the fragmentation excitation process during the breakup reaction of $^{9}$Li on a $^{208}$Pb target at an incident energy of 32.7 MeV/nucleon. The resonant states are reconstructed from the final state coincident particles $t$+$t$ using the invariant mass method, while the non-resonant background is estimated using the event mixing method. Two states of energy level peaks at $13.9\pm0.3$ and $15.0\pm0.3$ MeV are observed. Microscopic cluster model calculations exploring the $t+t$ resonant states in $^6\mathrm{He}$ yield theoretical energy spectra which are then compared with the current experimental results. The calculated reduced width amplitudes (RWA) of the $t+t$ channels further confirm the clustering structure of the identified $t+t$ resonant states.
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Submitted 12 January, 2026; v1 submitted 7 March, 2025;
originally announced March 2025.
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Advancement of Photospheric Radius Expansion and Clocked Type-I X-Ray Burst Models with the New $^{22}$Mg$(α,p)^{25}$Al Reaction Rate Determined at Gamow Energy
Authors:
J. Hu,
H. Yamaguchi,
Y. H. Lam,
A. Heger,
D. Kahl,
A. M. Jacobs,
Z. Johnston,
S. W. Xu,
N. T. Zhang,
S. B. Ma,
L. H. Ru,
E. Q. Liu,
T. Liu,
S. Hayakawa,
L. Yang,
H. Shimizu,
C. B. Hamill,
A. St J. Murphy,
J. Su,
X. Fang,
K. Y. Chae,
M. S. Kwag,
S. M. Cha,
N. N. Duy,
N. K. Uyen
, et al. (12 additional authors not shown)
Abstract:
We report the first (in)elastic scattering measurement of $^{25}\mathrm{Al}+p$ with the capability to select and measure in a broad energy range the proton resonances in $^{26}$Si contributing to the $^{22}$Mg$(α,p)$ reaction at type I x-ray burst energies. We measured spin-parities of four resonances above the $α$ threshold of $^{26}$Si that are found to strongly impact the $^{22}$Mg$(α,p)$ rate.…
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We report the first (in)elastic scattering measurement of $^{25}\mathrm{Al}+p$ with the capability to select and measure in a broad energy range the proton resonances in $^{26}$Si contributing to the $^{22}$Mg$(α,p)$ reaction at type I x-ray burst energies. We measured spin-parities of four resonances above the $α$ threshold of $^{26}$Si that are found to strongly impact the $^{22}$Mg$(α,p)$ rate. The new rate advances a state-of-the-art model to remarkably reproduce light curves of the GS 1826$-$24 clocked burster with mean deviation $<9$ % and permits us to discover a strong correlation between the He abundance in the accreting envelope of photospheric radius expansion burster and the dominance of $^{22}$Mg$(α,p)$ branch.
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Submitted 20 October, 2021; v1 submitted 10 August, 2021;
originally announced August 2021.
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Probing the nature of the conjectured low-spin wobbling bands in atomic nuclei
Authors:
S. Guo,
X. H. Zhou,
C. M. Petrache,
E. A. Lawrie,
S. Mthembu,
Y. D. Fang,
H. Y. Wu,
H. L. Wang,
H. Y. Meng,
G. S. Li,
Y. H. Qiang,
J. G. Wang,
M. L. Liu,
Y. Zheng,
B. Ding,
W. Q. Zhang,
A. Rohilla,
K. R. Mukhi,
Y. Y. Yang,
H. J. Ong,
J. B. Ma,
S. W. Xu,
Z. Bai,
H. L. Fan,
J. F. Huang
, et al. (6 additional authors not shown)
Abstract:
Precession is a unique motion in which the orientation of the rotational axis of a rotating body is not fixed but moving, and it generally exists in the Universe from giant stars through tiny atomic nuclei. In principle, the precession of an atomic nuclide can be approximately described as wobbling motion, arising from the coupling of a rotation and a harmonic vibration. Recently, a number of wobb…
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Precession is a unique motion in which the orientation of the rotational axis of a rotating body is not fixed but moving, and it generally exists in the Universe from giant stars through tiny atomic nuclei. In principle, the precession of an atomic nuclide can be approximately described as wobbling motion, arising from the coupling of a rotation and a harmonic vibration. Recently, a number of wobbling bands were reported at low spin, which violate the wobbling approximation that can be valid only at high spin. Here we explore the nature of the reported low-spin wobbling bands. Via a new experiment, we demonstrate that one such band in $^{187}$Au is generated by dominant single-particle excitation rather than by the excitation of a wobbling phonon. We point out that the imperfect research paradigm used previously would lead to unreliable identification of low-spin wobbling bands. Consequently, new experimental approaches should be developed to distinguish among the different excitation mechanisms that can give rise to the observed low-spin bands in odd-even nuclei.
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Submitted 18 September, 2021; v1 submitted 29 November, 2020;
originally announced November 2020.
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Constraining the $^{12}$C+$^{12}$C astrophysical S-factors with the $^{12}$C+$^{13}$C measurements at very low energies
Authors:
N. T. Zhang,
X. Y. Wang,
H. Chen,
Z. J. Chen,
W. P. Lin,
W. Y. Xin,
S. W. Xu,
D. Tudor,
A. I. Chilug,
I. C. Stefanescu,
M. Straticiuc,
I. Burducea,
D. G. Ghita,
R. Margineanu,
C. Gomoiu,
A. Pantelica,
D. Chesneanu,
L. Trache,
X. D. Tang,
B. Bucher,
L. R. Gasques,
K. Hagino,
S. Kubono,
Y. J. Li,
C. J. Lin
, et al. (2 additional authors not shown)
Abstract:
We use an underground counting lab with an extremely low background to perform an activity measurement for the $^{12}$C+$^{13}$C system with energies down to $E\rm_{c.m.}$=2.323 MeV, at which the $^{12}$C($^{13}$C,$p$)$^{24}$Na cross section is found to be 0.22(7) nb. The $^{12}$C+$^{13}$C fusion cross section is derived with a statistical model calibrated using experimental data. Our new result o…
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We use an underground counting lab with an extremely low background to perform an activity measurement for the $^{12}$C+$^{13}$C system with energies down to $E\rm_{c.m.}$=2.323 MeV, at which the $^{12}$C($^{13}$C,$p$)$^{24}$Na cross section is found to be 0.22(7) nb. The $^{12}$C+$^{13}$C fusion cross section is derived with a statistical model calibrated using experimental data. Our new result of the $^{12}$C+$^{13}$C fusion cross section is the first decisive evidence in the carbon isotope systems which rules out the existence of the astrophysical S-factor maximum predicted by the phenomenological hindrance model, while confirming the rising trend of the S-factor towards lower energies predicted by other models, such as CC-M3Y+Rep, DC-TDHF, KNS, SPP and ESW. After normalizing the model predictions with our data, a more reliable upper limit is established for the $^{12}$C+$^{12}$C fusion cross sections at stellar energies.
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Submitted 16 September, 2019;
originally announced September 2019.
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A proposed direct measurement of cross section at Gamow window for key reaction $^{19}$F($p$,$α$)$^{16}$O in Asymptotic Giant Branch stars with a planned accelerator in CJPL
Authors:
J. J. He,
S. W. Xu,
S. B. Ma,
J. Hu,
L. Y. Zhang,
C. B. Fu,
N. T. Zhang,
G. Lian,
J. Su,
Y. J. Li,
S. Q. Yan,
Y. P. Shen,
S. Q. Hou,
B. L. Jia,
T. Zhang,
X. P. Zhang,
B. Guo,
S. Kubono,
W. P. Liu
Abstract:
In 2014, the National Natural Science Foundation of China (NSFC) approved the Jinping Underground Nuclear Astrophysics laboratory (JUNA) project, which aims at direct cross-section measurements of four key stellar nuclear reactions right down to the Gamow windows. In order to solve the observed fluorine overabundances in Asymptotic Giant Branch (AGB) stars, measuring the key $^{19}$F($p$,$α$)…
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In 2014, the National Natural Science Foundation of China (NSFC) approved the Jinping Underground Nuclear Astrophysics laboratory (JUNA) project, which aims at direct cross-section measurements of four key stellar nuclear reactions right down to the Gamow windows. In order to solve the observed fluorine overabundances in Asymptotic Giant Branch (AGB) stars, measuring the key $^{19}$F($p$,$α$)$^{16}$O reaction at effective burning energies (i.e., at Gamow window) is established as one of the scientific research sub-projects. The present paper describes this sub-project in details, including motivation, status, experimental setup, yield and background estimation, aboveground test, as well as other relevant reactions.
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Submitted 25 May, 2016;
originally announced May 2016.
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Examination of the role of the $^{14}$O($α$,$p$)$^{17}$F reaction rate in type I x-ray bursts
Authors:
J. Hu,
J. J. He,
A. Parikh,
S. W. Xu,
H. Yamaguchi,
D. Kahl,
P. Ma,
J. Su,
H. W. Wang,
T. Nakao,
Y. Wakabayashi,
T. Teranishi,
K. I. Hahn,
J. Y. Moon,
H. S. Jung,
T. Hashimoto,
A. A. Chen,
D. Irvine,
C. S. Lee,
S. Kubono
Abstract:
The $^{14}$O($α$,$p$)$^{17}$F reaction is one of the key reactions involved in the breakout from the hot-CNO cycle to the rp-process in type I x-ray bursts (XRBs). The resonant properties in the compound nucleus $^{18}$Ne have been investigated through resonant elastic scattering of $^{17}$F+$p$. The radioactive $^{17}$F beam was separated by the CNS Radioactive Ion Beam separator (CRIB) and bomba…
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The $^{14}$O($α$,$p$)$^{17}$F reaction is one of the key reactions involved in the breakout from the hot-CNO cycle to the rp-process in type I x-ray bursts (XRBs). The resonant properties in the compound nucleus $^{18}$Ne have been investigated through resonant elastic scattering of $^{17}$F+$p$. The radioactive $^{17}$F beam was separated by the CNS Radioactive Ion Beam separator (CRIB) and bombarded a thick H$_2$ gas target at 3.6 MeV/nucleon. The recoiling light particles were measured by three $Δ$E-E silicon telescopes at laboratory angles of $θ$$_{lab}$$\approx$3$^\circ$, 10$^\circ$ and 18$^\circ$, respectively. Five resonances at $E_{x}$=6.15, 6.28, 6.35, 6.85, and 7.05 MeV were observed in the excitation functions, and their spin-parities have been determined based on an $R$-matrix analysis. In particular, $J^π$=1$^-$ was firmly assigned to the 6.15-MeV state which dominates the thermonuclear $^{14}$O($α$,$p$)$^{17}$F rate below 2 GK. As well, a possible new excited state in $^{18}$Ne was observed at $E_{x}$=6.85$\pm$0.11 MeV with tentative $J$=0 assignment. This state could be the analog state of the 6.880 MeV (0$^{-}$) level in the mirror nucleus $^{18}$O, or a bandhead state (0$^+$) of the six-particle four-hole (6$p$-4$h$) band. A new thermonuclear $^{14}$O($α$,$p$)$^{17}$F rate has been determined, and the astrophysical impact of multiple recent rates has been examined using an XRB model. Contrary to previous expectations, we find only modest impact on predicted nuclear energy generation rates from using reaction rates differing by up to several orders of magnitude.
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Submitted 16 July, 2014;
originally announced July 2014.
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Investigation of thermonuclear $^{18}$Ne($α$,$p$)$^{21}$Na rate via resonant elastic scattering of $^{21}$Na+$p$
Authors:
L. Y. Zhang,
J. J. He,
A. Parikh,
S. W. Xu,
H. Yamaguchi,
D. Kahl,
S. Kubono,
P. Mohr,
J. Hu,
P. Ma,
S. Z. Chen,
Y. Wakabayashi,
H. W. Wang,
W. D. Tian,
R. F. Chen,
B. Guo,
T. Hashimoto,
Y. Togano,
S. Hayakawa,
T. Teranishi,
N. Iwasa,
T. Yamada,
T. Komatsubara,
Y. H. Zhang,
X. H. Zhou
Abstract:
The $^{18}$Ne($α$,$p$)$^{21}$Na reaction is thought to be one of the key breakout reactions from the hot CNO cycles to the rp-process in type I x-ray bursts. In this work, the resonant properties of the compound nucleus $^{22}$Mg have been investigated by measuring the resonant elastic scattering of $^{21}$Na+$p$. An 89 MeV $^{21}$Na radioactive beam delivered from the CNS Radioactive Ion Beam Sep…
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The $^{18}$Ne($α$,$p$)$^{21}$Na reaction is thought to be one of the key breakout reactions from the hot CNO cycles to the rp-process in type I x-ray bursts. In this work, the resonant properties of the compound nucleus $^{22}$Mg have been investigated by measuring the resonant elastic scattering of $^{21}$Na+$p$. An 89 MeV $^{21}$Na radioactive beam delivered from the CNS Radioactive Ion Beam Separator bombarded an 8.8 mg/cm$^2$ thick polyethylene (CH$_{2}$)$_{n}$ target. The $^{21}$Na beam intensity was about 2$\times$10$^{5}$ pps, with a purity of about 70% on target. The recoiled protons were measured at the center-of-mass scattering angles of $θ_{c.m.}$$\approx$175.2${^\circ}$, 152.2${^\circ}$, and 150.5${^\circ}$ by three sets of $ΔE$-$E$ telescopes, respectively. The excitation function was obtained with the thick-target method over energies $E_x$($^{22}$Mg)=5.5--9.2 MeV. In total, 23 states above the proton-threshold in $^{22}$Mg were observed, and their resonant parameters were determined via an $R$-matrix analysis of the excitation functions. We have made several new $J^π$ assignments and confirmed some tentative assignments made in previous work. The thermonuclear $^{18}$Ne($α$,$p$)$^{21}$Na rate has been recalculated based on our recommended spin-parity assignments. The astrophysical impact of our new rate has been investigated through one-zone postprocessing x-ray burst calculations. We find that the $^{18}$Ne($α$,$p$)$^{21}$Na rate significantly affects the peak nuclear energy generation rate, reaction fluxes, as well as the onset temperature of this breakout reaction in these astrophysical phenomena.
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Submitted 18 March, 2014;
originally announced March 2014.
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Properties of resonant states in 18Ne relevant to key 14O(alpha,p)17F breakout reaction in type I x-ray bursts
Authors:
J. Hu,
J. J. He,
A. Parikh,
S. W. Xu,
H. Yamaguchi,
D. Kahl,
P. Ma,
J. Su,
H. W. Wang,
T. Nakao,
Y. Wakabayashi,
T. Teranishi,
K. I. Hahn,
J. Y. Moon,
H. S. Sung,
T. Hashimoto,
A. A. Chen,
D. Irvine,
C. S. Lee,
S. Kubono
Abstract:
The $^{14}$O($α$,$p$)$^{17}$F reaction is one of the key reactions involved in the breakout from the hot-CNO cycle to the rp-process in type I x-ray bursts. The resonant properties in the compound nucleus $^{18}$Ne have been investigated through resonant elastic scattering of $^{17}$F+$p$. The radioactive $^{17}$F beam was separated by the CNS Radioactive Ion Beam separator (CRIB) and bombarded a…
▽ More
The $^{14}$O($α$,$p$)$^{17}$F reaction is one of the key reactions involved in the breakout from the hot-CNO cycle to the rp-process in type I x-ray bursts. The resonant properties in the compound nucleus $^{18}$Ne have been investigated through resonant elastic scattering of $^{17}$F+$p$. The radioactive $^{17}$F beam was separated by the CNS Radioactive Ion Beam separator (CRIB) and bombarded a thick H$_2$ gas target at 3.6 MeV/nucleon. The recoiling light particles were measured by using three $Δ$E-E silicon telescopes at laboratory angles of $θ$$_{lab}$$\approx$3$^\circ$, 10$^\circ$ and 18$^\circ$, respectively. Five resonances at $E_{x}$=6.15, 6.28, 6.35, 6.85, and 7.05 MeV were observed in the excitation functions. Based on an $R$-matrix analysis, $J^π$=1$^-$ was firmly assigned to the 6.15-MeV state. This state dominates the thermonuclear $^{14}$O($α$,$p$)$^{17}$F rate below 1 GK. We have also confirmed the existence and spin-parities of three states between 6.1 and 6.4 MeV. As well, a possible new excited state in $^{18}$Ne was observed at $E_{x}$=6.85$\pm$0.11 MeV and tentatively assigned as $J$=0. This state could be the analog state of the 6.880 MeV (0$^{-}$) level in the mirror nucleus $^{18}$O, or a bandhead state (0$^+$) of the six-particle four-hole (6$p$-4$h$) band. A new thermonuclear rate of the $^{14}$O($α$,$p$)$^{17}$F reaction has been determined, and its astrophysical impact has been examined within the framework of one-zone x-ray burst postprocessing calculations.
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Submitted 9 March, 2014;
originally announced March 2014.
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The performance of a double sided silicon strip detector as a transmission detector for heavy ions
Authors:
J L Han,
J B Ma,
X G Cao,
Q Wang,
J S Wang,
Y Y Yang,
P Ma,
M R Huang,
S L Jin,
X J Rong,
Z Bai,
F Fu,
Q Hu,
R F Chen,
S W Xu,
J B Chen,
L Jin,
Y Li,
M H Zhao,
H S Xu
Abstract:
The performance of a double sided silicon strip detector (DSSSD), used for position and energy detection of heavy ions, is reported. The analysis shows that the incomplete charge collection (ICC) and charge sharing (CS) effects of the DSSSD give rise to a loss of energy resolution, however the position information is recorded without ambiguity. Representations of ICC/CS events in the energy spectr…
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The performance of a double sided silicon strip detector (DSSSD), used for position and energy detection of heavy ions, is reported. The analysis shows that the incomplete charge collection (ICC) and charge sharing (CS) effects of the DSSSD give rise to a loss of energy resolution, however the position information is recorded without ambiguity. Representations of ICC/CS events in the energy spectra are shown and their origins are confirmed by correlation analysis of the spectra from both junction side and ohmic side of the DSSSD.
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Submitted 15 July, 2013;
originally announced July 2013.
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A confirmative spin-parity assignment for the key 6.15 MeV state in $^{18}$Ne of astrophysical importance
Authors:
J. Hu,
J. J. He,
S. W. Xu,
H. Yamaguchi,
K. David,
P. Ma,
J. Su,
H. W. Wang,
T. Nakao,
Y. Wakabayashi,
T. Teranishi,
J. Y. Moon,
H. S. Jung,
T. Hashimoto,
A. Chen,
D. Irvine,
S. Kubono
Abstract:
Proton resonant states in $^{18}$Ne have been investigated by the resonant elastic scattering of $^{17}$F+$p$. The $^{17}$F beam was separated by the CNS radioactive ion beam separator (CRIB), and bombarded a thick H$_2$ gas target at 3.6 MeV/nucleon. The recoiled light particles were measured by using three sets of $Δ$E-E Si telescope at scattering angles of $θ$$_{lab}$$\approx 3^\circ$, 10…
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Proton resonant states in $^{18}$Ne have been investigated by the resonant elastic scattering of $^{17}$F+$p$. The $^{17}$F beam was separated by the CNS radioactive ion beam separator (CRIB), and bombarded a thick H$_2$ gas target at 3.6 MeV/nucleon. The recoiled light particles were measured by using three sets of $Δ$E-E Si telescope at scattering angles of $θ$$_{lab}$$\approx 3^\circ$, 10$^\circ$ and 18$^\circ$, respectively. Four resonances, {\it i.e.}, at $E_{x}$=6.15, 6.30, 6.85, and 7.05 MeV, were observed clearly. By $R$-matrix analysis of the excitation functions, $J^π$=1$^-$ was firmly assigned to the 6.15 MeV state which is a key state in calculating the reaction rate of $^{14}$O($α$,$p$)$^{17}$F reaction. This reaction was thought to be one of the most probable key reactions for the breakout from the hot-CNO cycle to the $rp$-process in type I x-ray bursts In addition, a new excited state observed at $E_{x}$=6.85 MeV was tentatively assigned as 0$^{-}$, which could be the analog state of 6.880 MeV, 0$^{-}$ in mirror $^{18}$O.
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Submitted 16 June, 2013;
originally announced June 2013.
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The 18Ne(a,p)21Na breakout reaction in x-ray bursts: experimental determination of spin-parities for alpha resonances in 22Mg via resonant elastic scattering of 21Na+p
Authors:
J. J. He,
L. Y. Zhang,
A. Parikh,
S. W. Xu,
H. Yamaguchi,
D. Kahl,
S. Kubono,
J. Hu,
P. Ma,
S. Z. Chen,
Y. Wakabayashi,
B. H. Sun,
H. W. Wang,
W. D. Tian,
R. F. Chen,
B. Guo,
T. Hashimoto,
Y. Togano,
S. Hayakawa,
T. Teranishi,
N. Iwasa,
T. Yamada,
T. Komatsubara
Abstract:
The $^{18}$Ne($α$,$p$)$^{21}$Na reaction provides a pathway for breakout from the hot CNO cycles to the $rp$-process in type I x-ray bursts. To better determine this astrophysical reaction rate, the resonance parameters of the compound nucleus $^{22}$Mg have been investigated by measuring the resonant elastic scattering of $^{21}$Na+$p$. An 89 MeV $^{21}$Na radioactive ion beam was produced at the…
▽ More
The $^{18}$Ne($α$,$p$)$^{21}$Na reaction provides a pathway for breakout from the hot CNO cycles to the $rp$-process in type I x-ray bursts. To better determine this astrophysical reaction rate, the resonance parameters of the compound nucleus $^{22}$Mg have been investigated by measuring the resonant elastic scattering of $^{21}$Na+$p$. An 89 MeV $^{21}$Na radioactive ion beam was produced at the CNS Radioactive Ion Beam Separator and bombarded an 8.8 mg/cm$^2$ thick polyethylene target. The recoiled protons were measured at scattering angles of $θ_{c.m.}$$\approx 175 {^\circ}$ and 152${^\circ}$ by three $ΔE$-$E$ silicon telescopes. The excitation function was obtained with a thick-target method over energies $E_x$($^{22}$Mg)=5.5--9.2 MeV. The resonance parameters have been determined through an $R$-matrix analysis. For the first time, the $J^π$ values for ten states above the alpha threshold in $^{22}$Mg have been experimentally determined in a single consistent measurement. We have made three new $J^π$ assignments and confirmed seven of the ten tentative assignments in the previous work. The $^{18}$Ne($α$,$p$)$^{21}$Na reaction rate has been recalculated, and the astrophysical impact of our new rate has been investigated through one-zone postprocessing x-ray burst calculations. We find that the $^{18}$Ne($α$,$p$)$^{21}$Na rate significantly affects the peak nuclear energy generation rate and the onset temperature of this breakout reaction in these phenomena.
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Submitted 22 July, 2013; v1 submitted 17 January, 2013;
originally announced January 2013.
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Determination of astrophysical 12N(p,g)13O reaction rate from the 2H(12N, 13O)n reaction and its astrophysical implications
Authors:
B. Guo,
J. Su,
Zhihong Li,
Y. B. Wang,
S. Q. Yan,
Y. J. Li,
N. C. Shu,
Y. L. Han,
X. X. Bai,
Y. S. Chen,
W. P. Liu,
H. Yamaguchi,
D. N. Binh,
T. Hashimoto,
S. Hayakawa,
D. Kahl,
S. Kubono,
J. J. He,
J. Hu,
S. W. Xu,
N. Iwasa,
N. Kume,
Zhihuan Li
Abstract:
The evolution of massive stars with very low-metallicities depends critically on the amount of CNO nuclides which they produce. The $^{12}$N($p$,\,$γ$)$^{13}$O reaction is an important branching point in the rap-processes, which are believed to be alternative paths to the slow 3$α$ process for producing CNO seed nuclei and thus could change the fate of massive stars. In the present work, the angul…
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The evolution of massive stars with very low-metallicities depends critically on the amount of CNO nuclides which they produce. The $^{12}$N($p$,\,$γ$)$^{13}$O reaction is an important branching point in the rap-processes, which are believed to be alternative paths to the slow 3$α$ process for producing CNO seed nuclei and thus could change the fate of massive stars. In the present work, the angular distribution of the $^2$H($^{12}$N,\,$^{13}$O)$n$ proton transfer reaction at $E_{\mathrm{c.m.}}$ = 8.4 MeV has been measured for the first time. Based on the Johnson-Soper approach, the square of the asymptotic normalization coefficient (ANC) for the virtual decay of $^{13}$O$_\mathrm{g.s.}$ $\rightarrow$ $^{12}$N + $p$ was extracted to be 3.92 $\pm$ 1.47 fm$^{-1}$ from the measured angular distribution and utilized to compute the direct component in the $^{12}$N($p$,\,$γ$)$^{13}$O reaction. The direct astrophysical S-factor at zero energy was then found to be 0.39 $\pm$ 0.15 keV b. By considering the direct capture into the ground state of $^{13}$O, the resonant capture via the first excited state of $^{13}$O and their interference, we determined the total astrophysical S-factors and rates of the $^{12}$N($p$,\,$γ$)$^{13}$O reaction. The new rate is two orders of magnitude slower than that from the REACLIB compilation. Our reaction network calculations with the present rate imply that $^{12}$N($p,\,γ$)$^{13}$O will only compete successfully with the $β^+$ decay of $^{12}$N at higher ($\sim$two orders of magnitude) densities than initially predicted.
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Submitted 21 November, 2012;
originally announced November 2012.
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Reevaluation of the $^{14}$O($α$,p)$^{17}$F Resonant Reaction Rate
Authors:
J. J. He,
H. W. Wang,
J. Hu,
S. W. Xu
Abstract:
The reaction rates of the key stellar reaction of $^{14}$O($α$,p)$^{17}$F have been reevaluated. It is thought that the previous 1$^-$ assignment for the 6.15-MeV state is incorrect by a careful reanalysis of the previous experimental data [J. Gómez del Campo {\it et al.}, Phys. Rev. Lett. {\bf 86}, 43 (2001)]. Most probably, the 6.286-MeV state is the key 1$^-$ state and the 6.15-MeV state is a 2…
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The reaction rates of the key stellar reaction of $^{14}$O($α$,p)$^{17}$F have been reevaluated. It is thought that the previous 1$^-$ assignment for the 6.15-MeV state is incorrect by a careful reanalysis of the previous experimental data [J. Gómez del Campo {\it et al.}, Phys. Rev. Lett. {\bf 86}, 43 (2001)]. Most probably, the 6.286-MeV state is the key 1$^-$ state and the 6.15-MeV state is a 2$^-$ one, and hence the resonance at $E_x$=6.286 MeV ($J^π$=1$^-$) actually dominates the reaction rates in the temperature region of astrophysical interests. The newly calculated reaction rates for the $^{14}$O($α$,p)$^{17}$F reaction are quite different from the previous ones, for instance, it's only about 1/6 of the previous value around 0.4 GK, while it's about 2.4 times larger than the previous value around 2 GK. The astrophysical implications have been briefly discussed based on the present conclusions.
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Submitted 30 May, 2011;
originally announced May 2011.
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Investigation of excited states in $^{18}$Ne via resonant elastic scattering of $^{17}$F+p and its astrophysical implication in the stellar reaction of $^{14}$O($α$,$p$)$^{17}$F
Authors:
J. Hu,
J. J. He,
S. W. Xu,
Z. Q. Chen,
X. Y. Zhang,
J. S. Wang,
X. Q. Yu,
L. Li,
L. Y. Zhang,
Y. Y. Yang,
P. Ma,
X. H. Zhang,
Z. G. Hu,
Z. Y. Guo,
X. Xu,
X. H. Yuan,
W. Lu,
Y. H. Yu,
Y. D. Zang,
S. W. Tang,
R. P. Ye,
J. D. Chen,
S. L. Jin,
C. M. Du,
S. T. Wang
, et al. (13 additional authors not shown)
Abstract:
Properties of proton resonances in $^{18}$Ne have been investigated efficiently by utilizing a technique of proton resonant elastic scattering with a $^{17}$F radioactive ion (RI) beam and a thick proton target. A 4.22~MeV/nucleon $^{17}$F RI beam was produced via a projectile-fragmentation reaction, and subsequently separated by a Radioactive Ion Beam Line in Lanzhou ({\tt RIBLL}). Energy spectra…
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Properties of proton resonances in $^{18}$Ne have been investigated efficiently by utilizing a technique of proton resonant elastic scattering with a $^{17}$F radioactive ion (RI) beam and a thick proton target. A 4.22~MeV/nucleon $^{17}$F RI beam was produced via a projectile-fragmentation reaction, and subsequently separated by a Radioactive Ion Beam Line in Lanzhou ({\tt RIBLL}). Energy spectra of the recoiled protons were measured by two sets of $Δ$E-E silicon telescope at center-of-mass scattering angles of $θ_{c.m.}$$\approx$175${^\circ}$$\pm$5${^\circ}$, $θ_{c.m.}$$\approx$152${^\circ}$$\pm$8${^\circ}$, respectively. Several proton resonances in $^{18}$Ne were observed, and their resonant parameters have been determined by an $R$-matrix analysis of the differential cross sections in combination with the previous results. The resonant parameters are related to the reaction-rate calculation of the stellar $^{14}$O($α$,$p$)$^{17}$F reaction, which was thought to be the breakout reaction from the hot CNO cycles into the $rp$-process in x-ray bursters. Here, $J^π$=(3$^-$, 2$^-$) are tentatively assigned to the 6.15-MeV state which was thought the key 1$^-$ state previously. In addition, a doublet structure at 7.05 MeV are tentatively identified, and its contribution to the resonant reaction rate of $^{14}$O($α$,$p$)$^{17}$F could be enhanced by at least factors of about 4$\sim$6 in comparison with the previous estimation involving only a singlet. The present calculated resonant rates are much larger than those previous values, and it may imply that this breakout reaction could play a crucial role under x-ray bursters conditions.
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Submitted 7 September, 2010;
originally announced September 2010.
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Radioactive Ion Beam Physics and Nuclear Astrophysics in China
Authors:
Y. G. Ma,
X. Z. Cai,
W. Q. Shen,
W. L. Zhan,
Y. L. Ye,
W. P. Liu,
G. M. Jin,
X. H. Zhou,
S. W. Xu,
L. H. Zuo,
S. J. Zhu,
Z. H. Liu,
J. Meng
Abstract:
Based on the intermediate energy radioactive Ion Beam Line in Lanzhou (RIBLL) of Heavy Ion Research Facility in Lanzhou (HIRFL) and Low Energy Radioactive Ion Beam Line (GIRAFFE) of Beijing National Tandem Accelerator Lab (HI13), the radioactive ion beam physics and nuclear astrophysics will be researched in detail. The key scientific problems are: the nuclear structure and reaction for nuclear…
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Based on the intermediate energy radioactive Ion Beam Line in Lanzhou (RIBLL) of Heavy Ion Research Facility in Lanzhou (HIRFL) and Low Energy Radioactive Ion Beam Line (GIRAFFE) of Beijing National Tandem Accelerator Lab (HI13), the radioactive ion beam physics and nuclear astrophysics will be researched in detail. The key scientific problems are: the nuclear structure and reaction for nuclear far from $β$-stability line; the synthesize of new nuclides near drip lines and new super heavy nuclides; the properties of asymmetric nuclear matter with extra large isospin and some nuclear astro- reactions.
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Submitted 14 October, 2004;
originally announced October 2004.