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Shell-model studies of the astrophysical rp -process reactions S 34 (p,γ) Cl 35 and Cl 34g,m (p,γ) Ar 35

Richter, W. A.; Brown, B. A.; Longland, R.; Wrede, C.; Denissenkov, P.; Fry, C.; Herwig, F.; Kurtulgil, D.; Pignatari, M.; Reifarth, R.


W. A. Richter

B. A. Brown

R. Longland

C. Wrede

P. Denissenkov

C. Fry

F. Herwig

D. Kurtulgil

M. Pignatari

R. Reifarth


© 2020 American Physical Society. Background: Dust grains condensed in the outflows of presolar classical novae should have been present in the protosolar nebula. Candidates for such presolar nova grains have been found in primitive meteorites and can in principle be identified by their isotopic ratios, but the ratios predicted by state-of-the-art one-dimensional hydrodynamic models are uncertain due to nuclear-physics uncertainties. Purpose: To theoretically calculate the thermonuclear rates and uncertainties of the S34(p,γ)Cl35 and Cl34g,m(p,γ)Ar35 reactions and investigate their impacts on the predicted S34/S32 isotopic ratio for presolar nova grains. Method: A shell-model approach in a (0+1) ħω model space was used to calculate the properties of resonances in the S34(p,γ)Cl35 and Cl34g,m(p,γ)Ar35 reactions and their thermonuclear rates. Uncertainties were estimated using a Monte Carlo method. The implications of these rates and their uncertainties on sulfur isotopic nova yields were investigated using a postprocessing nucleosynthesis code. The rates for transitions from the ground state of Cl34 as well as from the isomeric first excited state of Cl34 were explicitly calculated. Results: At energies in the resonance region near the proton-emission threshold, many negative-parity states appear. Energies, spectroscopic factors, and proton-decay widths are reported. The resulting thermonuclear rates are compared with previous determinations. Conclusions: The shell-model calculations alone are sufficient to constrain the variation of the S34/S32 ratios to within about 30%. Uncertainties associated with other reactions must also be considered, but in general we find that the S34/S32 ratios are not a robust diagnostic to clearly identify presolar grains made from nova ejecta.


Richter, W. A., Brown, B. A., Longland, R., Wrede, C., Denissenkov, P., Fry, C., …Reifarth, R. (2020). Shell-model studies of the astrophysical rp -process reactions S 34 (p,γ) Cl 35 and Cl 34g,m (p,γ) Ar 35. Physical Review C, 102(2), Article 025801.

Journal Article Type Article
Acceptance Date May 28, 2020
Online Publication Date Aug 4, 2020
Publication Date 2020-08
Deposit Date Aug 17, 2020
Publicly Available Date Aug 17, 2020
Journal Physical Review C
Print ISSN 2469-9985
Electronic ISSN 2469-9993
Publisher American Physical Society
Peer Reviewed Peer Reviewed
Volume 102
Issue 2
Article Number 025801
Keywords Nuclear reactions; Nucleosynthesis in explosive environments; Shell model; Spectroscopic factors & electromagnetic moments
Public URL
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