Direct Measurement of Low-Energy Resonances in $^{31}$P(p,$\alpha$)$^{28}$Si and $^{35}$Cl(p,$\alpha$)$^{32}$S

Reaction cycles in explosive hydrogen burning in novae and X-ray bursts influence both the energy generation and the processing of material to higher masses. The $^{31}$P(p,$\alpha$)$^{28}$Si and $^{35}$Cl(p,$\alpha$)$^{32}$S reactions are thought to lead to the formation of reaction cycles in the Si-Ar region, but the strength of these cycles depends on the (p,$\gamma$)/(p,$\alpha$) reaction rate ratio. Previous attempts to measure the strength of low-energy resonances in $^{32}$S and $^{36}$Ar have relied on indirect methods or resulted only in setting upper limits for a number of the resonances of interest. We have measured the strength of low-energy resonances in $^{32}$S and $^{36}$Ar at Oak Ridge National Laboratory by using stable $^{31}$P and $^{35}$Cl beams and a differentially pumped windowless hydrogen gas target to detect p-$\alpha$ coincidences in arrays of silicon strip detectors. Details of the experimental configuration and results will be presented. $^{*}$This work is supported in part by the U.S. DOE and NSF.