# Radioactive ion beam studies of α, p process waiting points in X-Ray Bursts

#### Abstract

The nucleosynthetic flow in type I X-ray Bursts (XRBs) is driven by the triple-α, rp and α,p processes. Several intermediate mass nuclei, 22Mg, 26Si, 30S, and 34Ar, have been identified as possible candidates for waiting points in XRBs. When such a nucleus is reached, the flow stalls due to a (p, γ)-(γ, p) equilibrium and must await β decay unless the (α, p) reaction is fast enough to break out of the waiting point first. A method to study these αp-process reactions has been developed whereby the time-inverse reaction is studied in inverse kinematics using radioactive ion beams produced by the in-flight method at the Argonne National Laboratory ATLAS facility. These time-inverse reactions have been used to study all four of the α, p process waiting points via the p(25Al,22Mg)α, p(33Cl,30S)α, and p(37K, 34Ar)α reactions. The data from these studies have been used to determine rates for 22Mg(α, p)25Al, 26Si(α, p)29P, 30S(α, p) 33Cl, and 34Ar(α, p)37K and have also been compared with theoretical calculations. The results and possible implications for nucleosynthesis in XRBs will be discussed. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.

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