Inelastic Proton Scattering on Holmium-165 and Gadolinium-156

Abstract

Elastic and inelastic scattering of 17.5-MeV protons by the low-lying rotational levels of holmium-165 and gadolinium-156 has been studied using a telescopic array of solid-state detectors with a resolution of about 60 keV. Angular distributions were obtained for the ground state ($\frac{7}{2^{-}}$), first excited state ($\frac{9}{2^{-}}$), and second excited state ($\frac{11}{2^{-}}$) of holmium-165, and the ground state ($0^{+}$), first excited state ($2^{+}$), and second excited state ($4^{+}$) of gadolinium-156. The cross section for the first excited state of ${\mathrm{Ho}}^{165}$ is an order of magnitude below that of the ground state. The ratio of the first excited state of ${\mathrm{Ho}}^{165}$ to that of the second does not agree with the prediction given by first-order direct reaction theory. There is some evidence that the third excited state of ${\mathrm{Gd}}^{156}$ ($6^{+}$) is weakly excited by 17.5-MeV protons.