Limits on Heavy Neutrino Mass from Neutrinoless ββ Decays of ⁷⁶Ge and ⁸²Se

With calculated nuclear shell-model wave functions, the nuclear matrix elements of the 0vββ decay mediated by heavy Majorana neutrino in ⁷⁶Ge and ⁸²Se are discussed. The results show that the lower limit of heavy neutrino mass is about α² x l0⁶ GeV with a mixing parameter α.