Double β decay of [Formula Presented]

Abstract

The intensity of positron annihilation radiation emitted by a sample of natural chromium trioxide, [Formula Presented] containing 4.7 g of [Formula Presented] 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 [Formula Presented] 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 [Formula Presented] now representing an order of magnitude improvement over the existing result. © 2003 The American Physical Society.