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Title: Excited states of Ca 39 and their significance in nova nucleosynthesis

Abstract

Background: We report that discrepancies exist between the observed abundances of argon and calcium in oxygen-neon nova ejecta and those predicted by nova models. An improved characterization of the 38K(p,γ) 39Ca reaction rate over the nova temperature regime (~ 0.1-0.4 GK), and thus the nuclear structure of 39Ca above the proton threshold (5770.92(63) keV), is necessary to resolve these contradictions. Purpose: The present study was performed to search for low-spin proton resonances in the 38K + p system, and to improve the uncertainties in energies of the known astrophysically significant proton resonances in 39Ca. Methods: The level structure of 39Ca was investigated via high-resolution charged-particle spectroscopy with an Enge split-pole spectrograph using the 40Ca( 3He, α) 39Ca reaction. Differential cross sections were measured over 6 laboratory angles at 21 MeV. Distorted-wave Born approximation calculations were performed to constrain the spin-parity assignments of observed levels with special attention to those significant in determination of the 38K(p,γ) 39Ca reaction rate over the nova temperature regime. Results: The resonance energies corresponding to two out of three astrophysically important states at 6154(5) and 6472.2(24) keV are measured with better precision than previous charged-particle spectroscopy measurements. A tentatively new state is discovered at 5908(3) keV.more » The spin-parity assignments of a few of the astrophysically important resonances are determined. Conclusions: Lastly, the present 38K(p,γ) 39Ca upper limit thermonuclear reaction rate at 0.1-0.4 GK is higher than that determined in [Physical Review C 97 (2018) 025802] by at most a factor of 1.4 at 0.1 GK.« less

Authors:
 [1];  [1];  [1];  [2];  [1];  [1]
  1. North Carolina State Univ., Raleigh, NC (United States). Department of Physics; Duke Univ., Durham, NC (United States). Triangle Universities Nuclear Laboratory
  2. McMaster Univ., Hamilton, ON (Canada). Department of Physics & Astronomy
Publication Date:
Research Org.:
North Carolina State Univ., Raleigh, NC (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
OSTI Identifier:
1483394
Grant/Contract Number:  
SC0017799; FG02-97ER41041
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review C
Additional Journal Information:
Journal Volume: 98; Journal Issue: 5; Journal ID: ISSN 2469-9985
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 79 ASTRONOMY AND ASTROPHYSICS

Citation Formats

Setoodehnia, K., Marshall, C., Kelley, J. H., Liang, J., Portillo Chaves, F., and Longland, R.. Excited states of Ca39 and their significance in nova nucleosynthesis. United States: N. p., 2018. Web. doi:10.1103/PhysRevC.98.055804.
Setoodehnia, K., Marshall, C., Kelley, J. H., Liang, J., Portillo Chaves, F., & Longland, R.. Excited states of Ca39 and their significance in nova nucleosynthesis. United States. doi:10.1103/PhysRevC.98.055804.
Setoodehnia, K., Marshall, C., Kelley, J. H., Liang, J., Portillo Chaves, F., and Longland, R.. Mon . "Excited states of Ca39 and their significance in nova nucleosynthesis". United States. doi:10.1103/PhysRevC.98.055804.
@article{osti_1483394,
title = {Excited states of Ca39 and their significance in nova nucleosynthesis},
author = {Setoodehnia, K. and Marshall, C. and Kelley, J. H. and Liang, J. and Portillo Chaves, F. and Longland, R.},
abstractNote = {Background: We report that discrepancies exist between the observed abundances of argon and calcium in oxygen-neon nova ejecta and those predicted by nova models. An improved characterization of the 38K(p,γ) 39Ca reaction rate over the nova temperature regime (~ 0.1-0.4 GK), and thus the nuclear structure of 39Ca above the proton threshold (5770.92(63) keV), is necessary to resolve these contradictions. Purpose: The present study was performed to search for low-spin proton resonances in the 38K + p system, and to improve the uncertainties in energies of the known astrophysically significant proton resonances in 39Ca. Methods: The level structure of 39Ca was investigated via high-resolution charged-particle spectroscopy with an Enge split-pole spectrograph using the 40Ca(3He, α) 39Ca reaction. Differential cross sections were measured over 6 laboratory angles at 21 MeV. Distorted-wave Born approximation calculations were performed to constrain the spin-parity assignments of observed levels with special attention to those significant in determination of the 38K(p,γ) 39Ca reaction rate over the nova temperature regime. Results: The resonance energies corresponding to two out of three astrophysically important states at 6154(5) and 6472.2(24) keV are measured with better precision than previous charged-particle spectroscopy measurements. A tentatively new state is discovered at 5908(3) keV. The spin-parity assignments of a few of the astrophysically important resonances are determined. Conclusions: Lastly, the present 38K(p,γ) 39Ca upper limit thermonuclear reaction rate at 0.1-0.4 GK is higher than that determined in [Physical Review C 97 (2018) 025802] by at most a factor of 1.4 at 0.1 GK.},
doi = {10.1103/PhysRevC.98.055804},
journal = {Physical Review C},
number = 5,
volume = 98,
place = {United States},
year = {Mon Nov 26 00:00:00 EST 2018},
month = {Mon Nov 26 00:00:00 EST 2018}
}

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