Searching for the β+EC and EC/EC Decays of 74Se

Double beta decay (β+EC, EC/EC) of 74Se was investigated at the Modane underground laboratory (LSM, France; 4800 m of water equivalent) using the OBELIX ultralow-background HPGe detector with a sensitive volume of 600 cm3 and a sample of natural selenium with a mass of 1.6 kg containing ~0.89% (~14.24 g) of 74Se. The new experimental limits for β+EC and EC/EC decays of 74Se to ground 0+ and excited $$2_{1}^{ + },$$ 596 keV, and $$2_{2}^{ + },$$ 1204 keV states of 74Ge, were obtained from experimental data accumulated over 135 days.