New High-Spin IsomerHf179m2and Intraband Branchings in the Ground-State Rotational Sequence of

Abstract

A new high-spin isomer ''2Hf has been produced by irradiation of isotopically enriched GYb with m particles. To investigate its decay, Ge(Li) p-ray spectra, Si(Li) conversionelectron spectra, and NaI(Tl)-Ge(Li) and Ge{Li)-Ge(Li) y~c oincidence spectra have been recorded. y rays with energies 122.7, 146.2, 169.8, 192.8, 217.0, 236.6, 257.5, 268.9, 316.0, 362.6, 409.8, and 453.7 keV have been attributed to the decay of the isomer. These decay with a half-life of (29+1) day. The coincidence measurements establish that the quanta with energies 122.7 through 236.6 keV are in cascade, while the y rays with energies 268.9 through 453.7 keV represent crossover transitions within a rotational band with levels up to I= g built on the n~Hf ground state. The rotational-model quantity ig&gz)2/QO2 has been derived from y intensity measurements of the cascade and crossover transitions. It is constant within the experimental error for all members of the band. The values for the gyromagnetic ratios g& = -0.202 + 0.027 and g&= 0.160 + 0.014 have been deduced.