Measurements of ordinary muon capture rates on 100Mo and natural Mo for astro-antineutrinos and double-& beta; decays

Ordinary muon capture (OMC) rates are valuable for studying the neutrino nuclear responses of astrophysical antineutrinos and double-& beta; decays (DBDs). Currently, there is interest in experimental studies of the OMC rates and their mass number (A) dependence for 100Mo and natural Mo. To obtain these rates, a negative muon beam from the MuSIC facility at the Research Center for Nuclear Physics (RCNP), Osaka University was utilized. The half-lives of trapped muons were measured by using a muon stopping signal from a scintillation counter and the time distribution of the OMC nuclear gamma rays and the muon-decay electrons by Ge detectors. The present measurements yielded OMC rates for enriched and natural molybdenum of ?(100Mo) = (7.07 & PLUSMN; 0.32) x 106 s-1 and ?(natMo) = (9.66 & PLUSMN; 0.44) x 106 s-1, respectively. The observed OMC rate for 100Mo is approximately 27% smaller than that for natural Mo due to the blocking effect of the excess neutrons on the proton-to-neutron transformation in OMC. The present experimental observation is consistent with the Goulard-Primakoff (GP) and Primakoff (P) empirical equations. The impacts of the present results on the astro-antineutrinos and double-& beta; decays are discussed.