Study of the cadmium isotopes (I): Beta and gamma ray spectroscopy of Ag 110m

Abstract

Using a beta-ray spectrometer and scintillation spectrometers, beta-rays and gamma-rays following the decay of Ag 110m (250 d) were studied. The maximum energies of the four beta-rays were determined to be 0.53, 1.4, 2.18 and 2.87 MeV from the beta-ray spectrum. A beta-ray which has a maximum energy of about 0.084 MeV was observed, but the maximum energy could not be determined accurately because of the counter window absorption and the existence of the isomeric transition. From the internal conversion electron spectrum, fifteen gamma-rays were detected and the transition energies were measured to be 0.115, 0.4462, 0.6189, 0.6577, 0.676, 0.688, 0.7072, 0.7451, 0.7643, 0.8153, 0.8846, 0.9368, 1.382, 1.474 and 1.504 MeV. The 0.676 MeV and the 0.688 MeV gamma-rays were found. These new gamma-rays save the discrepancies among the gamma-ray intensities. Multipolarities of the gamma-rays were assigned, comparing the measured K/(L+M) ratios and the K-shell internal conversion coefficients with the theoretical values. Considering Ritz's law (the energy rule), Kirchhoff's law (the intensity rule), the cascade relation (the coincidence and the summing peak methods) and selection rule (the beta-ray forbiddenness and gamma-ray multipolarity), a decay scheme was proposed. The spins and parities of levels, relative intensities of gamma-rays and log ft of beta-rays were discussed from the viewpoint of nuclear structure. The spins of the levels of the second excited group were 2+ and 4+ and the energy ratios of these levels and the first excited level were about 2.3. These facts support the vibrational model. The higher excited states of Cd 110 and the energy and the multipolarity of the isomeric transition of Ag 110m are also discussed.