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

The Ar-34(alpha, p)K-37 reaction is believed to be one of the last in a sequence of (alpha, p) and (p, gamma) reactions within the T-z = -1, sd-shell nuclei, known as the alpha p-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 alpha p-process, stellar rates are calculated using a statistical model, such as Hauser-Feshbach. Questions on the applicability of a Hauser-Feshbach model for the Ar-34(alpha, p)K-37 reaction arise due to level density considerations in the compound nucleus, Ca-38. We have performed high energy-resolution forward-angle Ca-40(p, t)Ca-38 measurements with the K = 600 spectrograph at iThemba LABS in order to identify levels above the alpha-threshold in Ca-38. States identified in this work were then used to determine the Ar-34(alpha, p)K-37 reaction rate based on a narrow-resonance formalism. Comparisons are made to two standard Hauser-Feshbach model predicted rates at XRB temperatures.