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

Proton radioactivity from 117 La was re-investigated with much improved statistics and precision. Only the ground-state proton decay ( E p = 813 ( 3 ) keV , T 1 / 2 = 20.1 ( 25 ) ms ) was observed, no evidence for a previously reported isomeric proton decay was found. Prompt γ rays in 117 La were identified using the Recoil–Decay Tagging method. Overall the data indicate that the proton-emitting state is associated with a K π = 3 / 2 + configuration, in agreement with all the published proton-decay calculations and predictions for the ground-state configuration of 117 La 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 K π = 7 / 2 − configuration.