A search for double-electron capture in 74Se using coincidence/anticoincidence gamma-ray spectrometry

TL;DR

This study used gamma-ray spectrometry methods to search for double-electron capture in 74Se, setting a new lower limit on its half-life, but found no evidence of the process.

Contribution

It evaluates and compares gamma-ray spectrometry techniques for detecting double-electron capture in 74Se, establishing the most stringent half-life limit to date.

Findings

No evidence of double-electron capture in 74Se was observed.

The half-life limit was set at >1.5x10^19 years.

Coincidence and anticoincidence methods were assessed for sensitivity.

Abstract

Evaluation of single, coincidence and anticoincidence gamma-ray spectrometry methods has been carried out with the aim to search for double-electron capture in 74Se. This process is unique, because there is probability for transition to the 2+ excited state in 74Ge (1204 keV), and de-excitation through two gamma-quanta cascade with energies of 595.9 keV and 608.4 keV. Long-term measurements with anticosmic shielded HPGe spectrometer and the coincidence HPGe-NaI(Tl) spectrometer did not show any evidence for the double-electron capture in 74Se. The best limit for the half-life of the double electron capture in 74Se (both for the neutrinoless and two neutrino processes) was estimated to be >1.5x10E19 years.