Search forβ+EC and ECEC processes inSn112

Abstract

Limits on ${\ensuremath{\beta}}^{+}$EC (here EC denotes electron capture) and ECEC processes in $^{112}\mathrm{Sn}$ have been obtained using a $380 {\mathrm{cm}}^{3}$ HPGe detector and an external source consisting of 53.355 g enriched tin (94.32% of $^{112}\mathrm{Sn}$). A limit with 90% C.L. on the $^{112}\mathrm{Sn}$ half-life of $4.7\ifmmode\times\else\texttimes\fi{}{10}^{20}$ y for the ECEC($0\ensuremath{\nu}$) transition to the ${0}_{3}^{+}$ excited state in $^{112}\mathrm{Cd}$ (1871.0 keV) has been established. This transition is discussed in the context of a possible enhancement of the decay rate by several orders of magnitude given that the ECEC$(0\ensuremath{\nu})$ process is nearly degenerate with an excited state in the daughter nuclide. Prospects for investigating such a process in future experiments are discussed. The limits on other ${\ensuremath{\beta}}^{+}$EC and ECEC processes in $^{112}\mathrm{Sn}$ were obtained on the level of $(0.6\text{\ensuremath{-}}8.7)\ifmmode\times\else\texttimes\fi{}{10}^{20}$ y at the 90% C.L.