Decay scheme of 50V

TL;DR

This study measured the half-life of electron capture in $^{50}$V to be approximately 2.77×10^{17} years and set a lower limit of 8.9×10^{18} years for its beta decay, using ultra low-background detection underground.

Contribution

First precise measurement of $^{50}$V's electron-capture half-life and establishment of a new lower bound for its beta decay half-life using underground gamma spectroscopy.

Findings

Electron-capture half-life: (2.77^{+0.20}_{-0.19})×10^{17} years

Beta decay half-life lower bound: ≥8.9×10^{18} years

No beta decay detected within experimental sensitivity

Abstract

Investigation of the $^{50}$V electron-capture to the $2^+$ 1553.8 keV level of $^{50}$Ti and search for $\beta^-$ decay of $^{50}$V to the $2^+$ 783.3 keV level of $^{50}$Cr (both those decays are fourfold forbidden with $\Delta J^{\Delta \pi}=4^+$) have been performed using a vanadium sample of natural isotopic abundance with mass of 955 g. The measurements were conducted with the help of an ultra low-background HPGe-detector system located 225 m underground in the laboratory HADES (Belgium). The measured value of the half-life of $^{50}$V for electron capture was $T^{\mathrm{EC}}_{1/2}=(2.77^{+0.20}_{-0.19})\times 10^{17}$ yr. The $\beta^-$-decay branch was not detected and the corresponding lower bound of the half-life was $T^{\beta}_{1/2}\geq 8.9\times 10^{18}$ yr at the 90\% confidence level.