Double β decay of ⁵⁰Cr

Abstract

The intensity of positron annihilation radiation emitted by a sample of natural chromium trioxide, CrO3, containing 4.7 g of 50Cr, was measured for 30 days. The background was measured with samples of iron, copper, and no sample at all (air), during a similar period of time. From the net intensity of the 511-keV line in the HpGe coincidence spectrum the partial half-life for the positron-electron capture double beta decay of 50Cr, T1/2(β+ EC,2νv+0ν) = 1.3(12) × 1018 yr at the 95% CL was deduced. Alternatively, at 95% CL the effect may be considered absent, the resulting lower limit for this half-life of 1.3 × 1018 yr now representing an order of magnitude improvement over the existing result.