First observation of the electron capture of $^{76}$As

TL;DR

This paper reports the first observation of electron capture in $^{76}$As, providing precise measurements of its branching ratio, which is crucial for nuclear decay data and neutrinoless double-beta decay research.

Contribution

The study presents the first experimental detection and quantification of the electron capture process in $^{76}$As, with detailed branching ratio measurements.

Findings

Electron capture in $^{76}$As observed for the first time.

Branching ratio for EC/$eta^{+}$-channel measured as approximately 0.027.

Limits set on decay into excited and ground states of $^{76}$Ge.

Abstract

For a variety of radionuclides which decay via $\beta^{-}$ and a weak $\beta^{+}$-channel the electron-capture (EC) is not observed yet. As the interest of exact decay characteristica increased again, not least with the need of reliable data for experiments on investigation of the neutrinoless double-beta-decay, an experiment for the investigation of the $^{76}$As-EC was performed. The first time observation of the EC of $^{76}$As by this experiment resulted in a total branching-ratio for the EC / $\beta^{+}$-channel of $p_\mathrm{EC} = 0.0269 \pm \left(0.0080(\mathrm{stat.}) \pm 0.0029(\mathrm{sys.}) \right)$ and $p_\mathrm{EC} = 0.0263 \pm \left(0.0077(\mathrm{stat.}) \pm 0.0047(\mathrm{sys.}) \right)$ according to two different methods. For the branching of this decay-channel into the first excited- and the ground state of \gess a limit was obtained.