The decay of 72Hf 173

Abstract

The energy levels of 71Lu 173 have been studied from the electron-capture decay of 24.0-hour Hf 173, by means of high-resolution permanent-field electron spectrographs with and without “pre-acceleration”, a double-focusing spectrometer, scintillation spectrometers, and gamma-gamma coincidence techniques. Properties of the levels are discussed in terms of the unified model of Bohr and Mottelson and the single-particle model of Nilsson appropriate for spheroidally-deformed nuclei. The following intrinsic states are identified in Lu 173: 7 2 + [404], ground; 1 2 − [541], 128.2 keV; 5 2 + [402], 356.8 keV; and 1 2 + [411], 425.0 keV . The ground state of Hf 173 has the configuration 1 2 −[521] . The 1 2 −[541] orbital of Lu 173 is interesting in that it originates from the h 9 2 proton state beyond the 82-proton shell and also in the fact of its high decoupling parameter ( a = 4.2) which causes the I = 5 2 rotational state to be found below the I = 1 2 fundamental state. M1 and E2 relative transition probabilities within the 1 2 −[541] band are discussed, and the theoretical parameter b M1, upon which the M1 transition probability in a K = 1 2 band depends, is estimated both from the experimental results and from the Nilsson wave-functions. Log ft values of the Hf 173 decay are also discussed.