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

Abstract

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 $$_2$$ 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.