Nuclear γ-rays following muon capture

The identification of the nuclear γ-rays that occur when muon capture leads to excited nuclei made it possible to evaluate the distribution of excited nuclei formed after the capture process. Mono-isotopic elements were used as targets, and γ-ray spectra were recorded using Ge(Li) detectors. In most cases the observed γ-rays accounted for a high fraction of the capture process. It could be concluded that the probability of zero neutron emission after muon capture was less than 5 % contrary to the findings of Kaplan and the predictions of Singer. The chance of single neutron emission was highest, about 50 %, and it dropped with increasing neutron multiplicity. The probability of forming a particular excited state in an isotope was in general about proportional to the spin, and about inversely proportional to the energy of the state.