Two–neutrino double beta decay of Ge within deformed QRPA: A new suppression mechanism

The effect of deformation on the two-neutrino double decay (2νββ-decay) for ground state transition 76Ge → 76Se is studied in the framework of the deformed QRPA with separable Gamow-Teller residual interaction. A new suppression mechanism of the 2νββ-decay matrix element based on the difference in deformations of the initial and final nuclei is included. An advantage of this suppression mechanism in comparison with that associated with ground state correlations is that it allows a simultaneous description of the single β and the 2νββ-decay. By performing a detail calculation of the 2νββ-decay of 76Ge, it is found that the states of intermediate nucleus lying in the region of the Gamow-Teller resonance contribute significantly to the matrix element of this process. PACS numbers:23.40.BW,23.40.HC