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

Abstract

AbstractA 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$$_2$$ 2 (C$$_2$$ 2 O$$_4$$ 4 )$$_3$$ 3 powder sample was measured for 11.3 days with a total Yb exposure of 1.25 kg$$\times $$ × day. Half-life limits for $$\alpha $$ α -decay modes of $$^{168}\mathrm Yb$$ 168 Y b , $$^{170}\mathrm Yb$$ 170 Y b , $$^{171}\mathrm Yb$$ 171 Y b , $$^{172}\mathrm Yb$$ 172 Y b , $$^{173}\mathrm Yb$$ 173 Y b , $$^{174}\mathrm Yb$$ 174 Y b and $$^{176}\mathrm Yb$$ 176 Y b into the first excited states have been obtained between $$6\times 10^{14}$$ 6 × 10 14  years and $$2\times 10^{16}$$ 2 × 10 16  years. These are the first experimental constraints of these decay modes. Double electron capture of $$^{168}\mathrm Yb$$ 168 Y b and double beta decay of $$^{176}\mathrm Yb$$ 176 Y b into the first excited 2$$^+$$ + and 0$$^+$$ + states could be excluded with limits between $$1\times 10^{14}$$ 1 × 10 14  years to $$8\times 10^{16}$$ 8 × 10 16  years. This improves the experimental information on some of the decay modes compared to previous constraints.