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Title: Gamma-Ray Spectroscopy of Astrophysically Important States in {sup 39}Ca

Abstract

Background: Nova explosions synthesize elements up to A similar or equal to 40, and discrepancies exist between calculated and observed abundances of Ar and Ca created in the explosion. The K-38(p, gamma) Ca-39 reaction rate has been shown to be influential on these isotopic abundances at the endpoint of nova nucleosynthesis. The energies of the three most important resonances, corresponding to J(pi) = 5/2(+) excited states in the Ca-39 nucleus above the proton separation threshold, are uncertain and one has been measured with conflicting values [E-r = 679(2) versus E-r = 701(2) keV] in previous experiments. Purpose: Reducing the uncertainties on the resonance energies would allow for a better understanding of the reaction rate. To improve these uncertainties, we searched for gamma rays from the depopulation of the corresponding excited states in Ca-39. Methods: We report a new measurement of these resonance energies via the observation of previously unobserved gamma-ray transitions. These transitions were observed by studying the Ca-40(He-3, alpha gamma) Ca-39 reaction with Gammasphere ORRUBA Dual Detectors for Experimental Structure Studies (GODDESS). The updated resonance energies were then used to calculate the K-38(p, gamma)Ca-39 reaction rate and assess its uncertainties. Results: In total, 23 new transitions were found, includingmore » three gamma -ray transitions corresponding to the three J(pi)= 5/2(+) states of astrophysical interest at energies of 6156.2(16), 6268.8(22), and 6470.8(19) keV. These correspond to resonance energies in the K-38(p, gamma)Ca-39 reaction of 386(2), 498(2), and 701(2) keV. Conclusions: Updated K-38(p, gamma) Ca-39 reaction rate calculations show a reduced upper limit at nova temperatures. However, the lower-than-previously-measured energy of the 498-keV resonance and uncertainty in its resonance strength increases the upper limit of the rate close to previous estimates at 0.4 GK.« less

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science - Office of Nuclear Physics; National Science Foundation (NSF); USDOE National Nuclear Security Administration (NNSA); National Research Foundation of Korea (NRF)
OSTI Identifier:
1599769
DOE Contract Number:  
AC02-06CH11357
Resource Type:
Journal Article
Journal Name:
Physical Review. C, Nuclear Physics
Additional Journal Information:
Journal Volume: 101; Journal Issue: 1
Country of Publication:
United States
Language:
English

Citation Formats

Hall, M. R., Bardayan, D. W., Baugher, T., Lepailleur, A., Pain, S. D., Ratkiewicz, A., Ahn, S., Allen, J. M., Anderson, J. T., Ayangeakaa, A. D., Carpenter, M. P., Jiang, C. L., Seweryniak, D., and Zhu, S. Gamma-Ray Spectroscopy of Astrophysically Important States in {sup 39}Ca. United States: N. p., 2020. Web. doi:10.1103/PhysRevC.101.015804.
Hall, M. R., Bardayan, D. W., Baugher, T., Lepailleur, A., Pain, S. D., Ratkiewicz, A., Ahn, S., Allen, J. M., Anderson, J. T., Ayangeakaa, A. D., Carpenter, M. P., Jiang, C. L., Seweryniak, D., & Zhu, S. Gamma-Ray Spectroscopy of Astrophysically Important States in {sup 39}Ca. United States. doi:10.1103/PhysRevC.101.015804.
Hall, M. R., Bardayan, D. W., Baugher, T., Lepailleur, A., Pain, S. D., Ratkiewicz, A., Ahn, S., Allen, J. M., Anderson, J. T., Ayangeakaa, A. D., Carpenter, M. P., Jiang, C. L., Seweryniak, D., and Zhu, S. Wed . "Gamma-Ray Spectroscopy of Astrophysically Important States in {sup 39}Ca". United States. doi:10.1103/PhysRevC.101.015804.
@article{osti_1599769,
title = {Gamma-Ray Spectroscopy of Astrophysically Important States in {sup 39}Ca},
author = {Hall, M. R. and Bardayan, D. W. and Baugher, T. and Lepailleur, A. and Pain, S. D. and Ratkiewicz, A. and Ahn, S. and Allen, J. M. and Anderson, J. T. and Ayangeakaa, A. D. and Carpenter, M. P. and Jiang, C. L. and Seweryniak, D. and Zhu, S.},
abstractNote = {Background: Nova explosions synthesize elements up to A similar or equal to 40, and discrepancies exist between calculated and observed abundances of Ar and Ca created in the explosion. The K-38(p, gamma) Ca-39 reaction rate has been shown to be influential on these isotopic abundances at the endpoint of nova nucleosynthesis. The energies of the three most important resonances, corresponding to J(pi) = 5/2(+) excited states in the Ca-39 nucleus above the proton separation threshold, are uncertain and one has been measured with conflicting values [E-r = 679(2) versus E-r = 701(2) keV] in previous experiments. Purpose: Reducing the uncertainties on the resonance energies would allow for a better understanding of the reaction rate. To improve these uncertainties, we searched for gamma rays from the depopulation of the corresponding excited states in Ca-39. Methods: We report a new measurement of these resonance energies via the observation of previously unobserved gamma-ray transitions. These transitions were observed by studying the Ca-40(He-3, alpha gamma) Ca-39 reaction with Gammasphere ORRUBA Dual Detectors for Experimental Structure Studies (GODDESS). The updated resonance energies were then used to calculate the K-38(p, gamma)Ca-39 reaction rate and assess its uncertainties. Results: In total, 23 new transitions were found, including three gamma -ray transitions corresponding to the three J(pi)= 5/2(+) states of astrophysical interest at energies of 6156.2(16), 6268.8(22), and 6470.8(19) keV. These correspond to resonance energies in the K-38(p, gamma)Ca-39 reaction of 386(2), 498(2), and 701(2) keV. Conclusions: Updated K-38(p, gamma) Ca-39 reaction rate calculations show a reduced upper limit at nova temperatures. However, the lower-than-previously-measured energy of the 498-keV resonance and uncertainty in its resonance strength increases the upper limit of the rate close to previous estimates at 0.4 GK.},
doi = {10.1103/PhysRevC.101.015804},
journal = {Physical Review. C, Nuclear Physics},
number = 1,
volume = 101,
place = {United States},
year = {2020},
month = {1}
}

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