Exploring the possibility of bound-state double-β decay in bare atoms

Abstract

We investigate the possibility of bound-state double-β decay in bare atoms, in which one or two electrons remain in the bound atomic states rather than being emitted into the continuum. We calculate the phase space factors of both two-neutrino (2ν) and neutrinoless (0ν) double-β decay for possible candidates, and compare in detail the double-β decay rates in bare atoms with those in neutral atoms. In certain circumstances, it is found that the bound-state double-β decay could become a dominating channel in bare atoms and the decay rate could be increased significantly. Moreover, the phase space factors of 0ν double-β decay with two electrons remaining in the bound-states are analyzed by using the resonance enhancement theory. The occurrence of 0ν double-β decay in bare atoms is discussed and the possibility of such bound-state double-β decay can not be excluded.