Excited states of Ca39 and their significance in nova nucleosynthesis

K. Setoodehnia, C. Marshall, J. H. Kelley, J. Liang, F. Portillo Chaves, and R. Longland
Phys. Rev. C 98, 055804 – Published 26 November 2018

Abstract

Background: 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 K38(p,γ)Ca39 reaction rate over the nova temperature regime (0.10.4 GK), and thus the nuclear structure of Ca39 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 K38+p system, and to improve the uncertainties in energies of the known astrophysically significant proton resonances in Ca39.

Methods: The level structure of Ca39 was investigated via high-resolution charged-particle spectroscopy with an Enge split-pole spectrograph using the Ca40(He3,α)Ca39 reaction. Differential cross sections were measured over six 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 K38(p,γ)Ca39 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: The present K38(p,γ)Ca39 upper limit thermonuclear reaction rate at 0.1–0.4 GK is higher than that determined by Christian et al. [Phys. Rev. C 97, 025802 (2018)] by at most a factor of 1.4 at 0.1 GK.

  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Received 15 June 2018
  • Revised 16 October 2018

DOI:https://doi.org/10.1103/PhysRevC.98.055804

©2018 American Physical Society

Physics Subject Headings (PhySH)

Nuclear Physics

Authors & Affiliations

K. Setoodehnia1,2,*, C. Marshall1,2, J. H. Kelley1,2, J. Liang3, F. Portillo Chaves1,2, and R. Longland1,2

  • 1Department of Physics, North Carolina State University, Raleigh, North Carolina 27695, USA
  • 2Triangle Universities Nuclear Laboratory, Duke University, Durham, North Carolina 27710, USA
  • 3Department of Physics & Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada

  • *ksetood@ncsu.edu

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand
Issue

Vol. 98, Iss. 5 — November 2018

Reuse & Permissions
Access Options
CHORUS

Article Available via CHORUS

Download Accepted Manuscript
Author publication services for translation and copyediting assistance advertisement

Authorization Required


×
×

Images

×

Sign up to receive regular email alerts from Physical Review C

Log In

Cancel
×

Search


Article Lookup

Paste a citation or DOI

Enter a citation
×