Indirect study of the stellar ³⁴ Ar(α,p) ³⁷K reaction rate through ⁴⁰Ca(p,t) ³⁸Ca reaction measurements

Long, A. M. ; Adachi, T. ; Beard, M. ; Berg, G. P. A. ; Buthelezi, Z. ; Carter, J. ; Couder, M. ; deBoer, R. J. ; Fearick, R. W. ; Fortsch, S. V. ; Gorres, J. ; Mira, J. P. ; Murray, S. H. T. ; Neveling, R. ; Papka, P. ; Smit, F. D. ; Sideras-Haddad, E. ; Swartz, J. A. ; Talwar, R. ; Usman, I. T. ; Wiescher, M. ; Van Zyl, J. J. ; Volya, A. (2017)

CITATION: Long, A. M., et al. 2017. Indirect study of the stellar ³⁴ Ar(α,p) ³⁷K reaction rate through ⁴⁰Ca(p,t) ³⁸Ca reaction measurements. Physical Review C, 95(5):1-9, doi:10.1103/PhysRevC.95.055803.

The original publication is available at https://journals.aps.org/prc

Article

The ³⁴Ar(α,p)³⁷K reaction is believed to be one of the last in a sequence of (α,p) and (p,γ) reactions within the Tz=−1, sd-shell nuclei, known as the αp-process. This process is expected to influence the shape and rise times of luminosity curves coming from type I x-ray bursts (XRBs). With very little experimental information known on many of the reactions within the αp-process, stellar rates are calculated using a statistical model, such as Hauser-Feshbach. Questions on the applicability of a Hauser-Feshbach model for the ³⁴Ar(α,p) ³⁷K reaction arise due to level density considerations in the compound nucleus, 38Ca. We have performed high energy-resolution forward-angle ⁴⁰Ca(p,t)³⁸Ca measurements with the K=600 spectrograph at iThemba LABS in order to identify levels above the α-threshold in ³⁸Ca. States identified in this work were then used to determine the ³⁴Ar(α,p)³⁷K reaction rate based on a narrow-resonance formalism. Comparisons are made to two standard Hauser-Feshbach model predicted rates at XRB temperatures.

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