Abstract :
Experimental and theoretical study of the β− decay of 100Nb to the two-quasiparticle states in 100Mo suggests the opening of the Z=40 subshell gap in the proton pf-0g9/2 shell for isobars near 100Mo. Assuming the opening of the Z=40 subshell gap both for 100Mo and 100Ru enables the study of the effects of this subshell gap upon the two-neutrino and neutrinoless double-beta-decay rates of 100Mo to the ground state and excited states in 100Ru. It is found that the influence of the opening of the Z=40 gap has very minor effects on the beta-decay and double-beta-decay feeding of the 0+ and 2+ states of 100Ru.
