Decay of Hf180m

Abstract

The energies and relative intensities of the gamma radiation and the relative intensities of the conversion electrons following the decay of 5.5-hr Hf180m have been measured using the curved-crystal gamma-ray spectrometer (recently calibrated for accurate intensity measurements), the ring-focused beta-ray spectrometer, and the semicircular spectrometer at the California Institute of Technology. The measured transition energies are: 57.54±0.01, 93.33±0.02, 215.25±0.13, 332.5±0.3, and 443.8±0.6 kev. The energy levels deduced from these values are not entirely consistent with the two-parameter rotational formula. Conversion coefficients derived from the measurements were absolutely normalized using a method involving information available from the decay scheme. All of the 57.54-kev transition conversion coefficients are anomalously high if compared with the theoretical E1 coefficients. No admixture of M2+E3 can account for the anomaly. The K conversion coefficients of the E2 transitions are all about 10% low with exception of the 93.33-kev transition. The L coefficients have a varying deviation, the maximum being 12%. The K conversion coefficient of the 501.3-kev transition has the value 0.037±0.012 which is consistent with the theoretical E3 value of 0.040.