Structure of the proton emitter (117)La studied by proton and gamma-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 gamma rays in 117La were identified using the Recoil-Decay Tagging method. Overall the data indicate that the proton-emitting state is associated with a K(pi) = 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(pi) = 7/2(-) configuration. (C) 2011 Elsevier B.V. All rights reserved.