Emergence of triaxiality in 74Se from electric monopole transition strengths

Abstract

The structure of 74Se at low energy was investigated via spectroscopy of internal conversion electrons at the INFN Legnaro National Laboratories (LNL). A set of internal K-conversion coefficients and monopole transition strengths was measured. A large & rho;2(E0; 2+2-+ 2+1 ) & BULL; 103 = 210(130) value was deduced. This result, in addition to a low upper limit for the 0+3-+ 0+2 electron transition, casts in doubt a simple interpretation of the 74Se low-lying structure, in particular the recently proposed spherical, vibrational character. New microscopic beyond-mean-field calculations generally agree with the experimental results and are capable of producing a large & rho;2(E0; 2+2-+ 2+1 ) value, even if still a factor & AP;7 smaller than the experiment. Triaxiality and a complex shape-coexistence and mixing scenario seem responsible for this unexpected experimental result.& COPY; 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons .org /licenses /by /4 .0/). Funded by SCOAP3.