Search for rare alpha and double beta decays of Yb isotopes to excited levels of daughter nuclei

Abstract

A search for alpha and double beta decays of ytterbium isotopes was performed with an ultra low-background high purity germanium detector at Gran Sasso Underground Laboratory (Italy). A 194.7 g Yb_2(C_2O_4)_3 powder sample was measured for 11.3 days with a total Yb exposure of 1.25 kgtimes day. Half-life limits for alpha -decay modes of ^{168}mathrm Yb, ^{170}mathrm Yb, ^{171}mathrm Yb, ^{172}mathrm Yb, ^{173}mathrm Yb, ^{174}mathrm Yb and ^{176}mathrm Yb into the first excited states have been obtained between 6times 10^{14} years and 2times 10^{16} years. These are the first experimental constraints of these decay modes. Double electron capture of ^{168}mathrm Yb and double beta decay of ^{176}mathrm Yb into the first excited 2^+ and 0^+ states could be excluded with limits between 1times 10^{14} years to 8times 10^{16} years. This improves the experimental information on some of the decay modes compared to previous constraints.