Structure of the proton emitter 117La studied by proton and γ-ray spectroscopy

Proton radioactivity from 117La was re-investigated with much improved statistics and precision. Only the ground-state proton decay (Ep=813(3) keV, T1/2=20.1(25) ms) was observed, no evidence for a previously reported isomeric proton decay was found. Prompt γ rays in 117La were identified using the Recoil-Decay Tagging method. Overall the data indicate that the proton-emitting state is associated with a Kπ=3/2+ configuration, in agreement with all the published proton-decay calculations and predictions for the ground-state configuration of 117La calculated in the framework of either adiabatic or non-adiabatic particle models. However, this is not in agreement with the most recent state-of-the-art quasi-particle non-adiabatic model calculations which predict a Kπ=7/2− configuration.