Double electron capture searches in $^{74}$Se

TL;DR

This study searches for double electron capture in selenium-74 using a low-background detector, setting new lower limits on half-lives and questioning recent published results.

Contribution

It provides new experimental half-life limits for double electron capture in $^{74}$Se and critically assesses the validity of recent related findings.

Findings

Lower half-life limit of 0.70×10^19 years for $^{74}$Se double electron capture

Questioning the validity of some recent published limits

Use of ultralow background Ge-detector in Felsenkeller laboratory

Abstract

A search for various double electron capture modes of $^{74}$Se has been performed using an ultralow background Ge-detector in the Felsenkeller laboratory, Germany. Especially for the potentially resonant transition into the 1204.2 keV excited state of $^{74}$Ge a lower half-life limit of $0.70\cdot 10^{19}$ yr (90% credibility) has been obtained. Serious concerns are raised about the validity of obtained $^{74}$Se limits in some recent publications.