Investigation of double beta decay of 100Mo to excited states of 100Ru

Double beta decay of 100Mo to the excited states of daughter nuclei has been studied using a 600 cm3 low-background HPGe detector and an external source consisting of 2588 g of 97.5% enriched metallic 100Mo, which was formerly inside the NEMO-3 detector and used for the NEMO-3 measurements of 100Mo. The half-life for the two-neutrino double beta decay of 100Mo to the excited 01+ state in 100Ru is measured to be T1/2=[7.5±0.6(stat)±0.6(syst)]⋅1020 yrT1/2=[7.5±0.6(stat)±0.6(syst)]⋅1020 yr. For other (0ν+2ν)(0ν+2ν) transitions to the 21+, 22+, 02+, 23+ and 03+ levels in 100Ru, limits are obtained at the level of ∼(0.25–1.1)⋅1022 yr∼(0.25–1.1)⋅1022 yr.