The ( 3He, α) strength functions in rare-earth nuclei

Abstract

The 156Gd( 3He, α) 155Gd, 157Gd( 3He, α) 156Gd and 171Yb( 3He, α) 170Yb reactions have been studied over a wide region in excitation energy. The bombarding energy was 26 MeV, and the reaction products were analyzed by means of a particle telescope. Strength functions and angular distributions have been measured. All strength functions contain a strong low-energy peak which is shown to be the result of the Coriolis coupling. Additional αγ coincidence experiments were performed in order to study the population of the yrast levels as a function of excitation energy. These population patterns, as well as the α-particle angular distributions, are consistent with a dominating large- l transfer in the excitation region up to the neutron binding energy. Comparisons are made with calculated strength functions based on the particle-rotor model. Only a part of the total yield observed at high excitation energy can be accounted for by the model.