HIGH-ENERGY GAMOW-TELLER STRENGTH IN DOUBLE BETA-DECAY

The contribution of high-lying intermediate states to the two-neutrino double beta decay is investigated in several approximations. Even tho ugh there is an appreciable beta- strength at high energy connecting t he initial and intermediate nuclei, and a similar beta+ strength conne cting the intermediate and final nuclei, we conclude that the contribu tion of high-lying states to the betabeta decay is strongly suppressed due to the random nature of the corresponding beta- and beta+ amplitu des. At the same time, our approach suggests that in general the conve rgence of the double beta decay matrix elements as a function of the e xcitation energy in the intermediate nucleus is relatively fast. Thus, one expects that only one or few low-lying states are responsible for the bulk of the decay, in agreement with the available data.