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

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 Yb₂(C₂O₄)₃ powder sample was measured for 11.3 days with a total Yb exposure of 1.25 kg× day. Half-life limits for α-decay modes of ¹⁶⁸Y b, ¹⁷⁰Y b, ¹⁷¹Y b, ¹⁷²Y b, ¹⁷³Y b, ¹⁷⁴Y b and ¹⁷⁶Y b into the first excited states have been obtained between 6 × 10 ¹⁴ years and 2 × 10 ¹⁶ years. These are the first experimental constraints of these decay modes. Double electron capture of ¹⁶⁸Y b and double beta decay of ¹⁷⁶Y b into the first excited 2⁺ and 0⁺ states could be excluded with limits between 1 × 10 ¹⁴ years to 8 × 10 ¹⁶ years. This improves the experimental information on some of the decay modes compared to previous constraints.