First search for double ${\hat{I}}^2$ decay of dysprosium

Abstract

A search for double ${\hat{I}}^2$ decay of dysprosium was realized for the first time with the help of an ultra low-background HP Ge ${\hat{I}}^3$ detector. After 2512 h of data taking with a 322 g sample of dysprosium oxide limits on double beta processes in ${}^{156}$Dy and ${}^{158}$Dy have been established on the level of $T_{1/2}\ge 10^{14}-10^{16}$ yr. Possible resonant double electron captures in ${}^{156}$Dy and ${}^{158}$Dy were restricted on a similar level. As a by-product of the experiment we have measured the radioactive contamination of the Dy${}_2$O${}_3$ sample and set limits on the $\hat{I}\pm$ decay of dysprosium isotopes to the excited levels of daughter nuclei as $T_{1/2}\ge 10^{15}-10^{17}$ yr.

16 pages, 7 figures, 5 tables, submitted for publication