Unexpected properties of the $^{33}$S($\alpha$,p)$^{36}$Cl reaction cross section at low energies

Abstract

New experimental data for the $^{33}$S($\alpha$,p)$^{36}$Cl reaction show a very unusual energy dependence. Contrary to common findings for many other $\alpha$-induced reactions, statistical model calculations underestimate the measured cross sections at very low energies. The relatively huge cross sections at these low energies require a significant amount of single-particle strength in the measured energy range which exceeds by far 100% as soon as the additional strength from the competing $^{33}$S($\alpha$,n)$^{36}$Ar reaction is taken into account. In addition, the new data deviate from a general trend for the energy dependence of $\alpha$-induced reaction cross sections.