The strength of the analog and Gamow-Teller giant resonances and   hindrance of the 2\nu\beta\beta -decay rate
  An approach for describing the hindrance of the nuclear 2\nu\beta\beta-decay amplitude is proposed. The approach is based on a new formula obtained by a model-independent transformation of the initial expression for the amplitude. This formula takes explicitly into account the hindrance of the decay-amplitude due to the presence of the collective Gamow-Teller state. Calculations are performed within the simplest version of the approach. Calculated and experimental 2\nu\beta\beta halve-lives are compared for a wide range of nuclei. 
O.A.Rumyantsev, M.H.Urin