New Nuclear Structure and Decay Results in the 76Ge–76As System

Abstract

The process of neutrinoless double beta decay (0νββ) plays a key role in modern neutrino physics. Experiments on 76Ge 0νββ-decay using germanium semiconductors are at the forefront in this field. Due to the extremely low count rates expected for this rare decay, any kind of background event in the detector, especially at energies close to Qββ=2039.006 keV must be avoided. Therefore, a careful investigation on the neutron-induced background was carried out. In this scope experiments investigating the inelastic neutron excitation of the lower lying and the 69th excited level of 76Ge have been performed. The existence of a 2040.7 keV gamma-ray, that occurs by the de-excitation of the 69th excited level, was confirmed. Interfering background from 68Ge was studied via cross-section measurements of the natGe(n,jn)68Ge reaction using quasi-monoenergetic neutrons and accelerator mass specrometry for 68Ge detection. In order to explore the matrix element for the transition between the 76Ge-76As ground states, the electron–capture of 76As has been measured for the first time.