Virtual Double Beta Decays of Nuclei

Abstract

A theory of nuclear $2{\beta }$decay that includes $2{{{\beta }}^{ - }}$, $2{{{\beta }}^{ + }}$, ${{{\beta }}^{ + }},EC$, and $EC,EC$decays is constructed using results obtained in developing the theory of the two-proton decay of nuclei. The existence of two types of these decays is established. The first type corresponds to $2{\beta }$ decays that proceed via two sequential real ${\beta }$ decays of a parent nucleus and the compound nucleus generating from the parent nucleus. The second type is associated with the virtual nature of $2{\beta }$decays, the widths of which are described by formulas similar to the ones obtained earlier in the second order of perturbation theory in the Hamiltonian of weak interaction. The possibility is demonstrated of successfully describing experimental characteristics of the $2{\beta }$decay for a wide range of nuclei.