Neutron pair correlations in A=100 nuclei involved in neutrinoless double-β decay

The pairing properties of the neutrinoless double-β decay (0ν2β) candidate 100Mo have been studied, along with its daughter 100Ru, to provide input for nuclear matrix element calculations relevant to the decay. The (p,t) two-neutron transfer reaction was measured on nuclei of 102 ,100Ru and 100 ,98Mo. The experiment was designed to have particular sensitivity to 0 + states up to excitation energies of ∼3 MeV with high energy resolution. Measurements were made at two angles and L=0 transitions identified by the ratio of yields between the two angles. For the reactions leading to and from 100Ru, greater than 95% of the L=0 (p,t) strength was in the ground state, but in 100Mo about 20% was in excited 0 + states. The measured (p,t) data, together with existing (t,p) data, suggest that 100Mo is a shape-transitional nucleus while 100Ru is closer to the spherical side of that transition. Theoretical calculations of the 0ν2β nuclear matrix element may be complicated by this difference in shape. © 2012 American Physical Society.