Investigating the gamma-ray strength function in 74Ge using the ratio method

Abstract

An increasing number of measurements reveal the presence of a low-energy enhancement in the gamma-ray strength function (GSF). The GSF, which is the ability of nuclei to absorb or emit γ rays, provides insight into the statistical properties of atomic nuclei. For this project the GSF was studied for 74Ge which was populated in the reaction 74Ge(p,p’)74Ge* at a beam energy of 18 MeV. The data were collected with the STARS-LIBERACE array at Lawrence Berkeley National Laboratory. Silicon detector telescopes were used for particle identification and γ rays in coincidence were detected with 5 clover-type high-purity germanium detectors. Through the analysis particle-γ-γ coincidence events were constructed. These events, together with well-known energy levels, were used to identify primary γ rays from the quasicontinuum. Primary γ rays from a broad excitation energy region, which decay to six 2+ states could be identified. These states and the associated primary γ rays are used to measure the GSF for 74Ge with the Ratio Method [1], which entails taking ratios of efficiency-corrected primary γ-ray intensities from the quasicontinuum. Results from the analysis of the data and focus on the existence of the low-energy enhancement in 74Ge will be discussed.