Decays ofTa176,Lu

Abstract

The locations of 48 energy levels ln Hf have been deduced from p-ray singles, conversion-electron, and y-p coincidence measurements on the Ec-P decay of Ta. Over 300 pray transitions have been observed in the~Ta decay spectrum, and about 140 of these have been definitely assigned to the 7 Hf level scheme on the basis of 75 y-y coincidence spectra. Spin and parity assignments are proposed for 27 levels besides the ground-state rotationalband members. Less extensive y-ray singles data from Lu and Lu decay have also been obtained; these are found to be consistent with the 7 Hf level structure proposed on the basis of Ta decay data. Two 0+ excitations in 8Hf identified at 1150 and 1293 keV are found to display quite different decay properties. Evidence for the existence of a series of low-spin four-quasiparticle states near 3 MeV is cited. The Hf level structure is compared with available theoretical calculations, and a preliminary interpretati. on of several unusual features of the level scheme is presented.Counting was usually begun within three hours after the end of irradiation. Relatively small quantities of '"Ta, '"Ta, and "8Ta contamination were noted in the y-ray spectra.

Evolution of E2 strength in the rare-earth isotopes Hf174,176,178,180

“…with the internal conversion coefficients taken from BrIccFO [40]. The decay of 176 Ta to 176 Hf via electron capture results in a complicated decay scheme with many transitions [41,42], in comparison to the decay of 178 Hf, as can be seen from Figure 3 1 state is lower than the adopted value given in [11] but in agreement with other measurements, e.g. [43].…”

“…The 2 − 1 and 3 − 1 states have been assigned as members of a K π = 2 − band by [41,42]. The expected E1 decay transitions from this band to the yrast band are first forbidden transitions (∆K = 2) according to the Alaga rules [55] and from conversionelectron data a large admixture of M 2 and E3 has been confirmed for the decay transitions of the 2 − 1 state [41]. The decay transitions of the 3 − 1 state were assigned to have E1 character.…”