HIGH-K DECAYS AND LIFETIME MEASUREMENTS IN HF-172

The known level scheme of Hf-172 has been extended with three new coll ective rotational bands. Many new transitions have also been observed which link the known bands into the lower-spin states, thereby permitt ing unambiguous spin and parity assignments to be made for the first t ime. In particular seven low-intensity gamma-ray transitions have been established which link the K = 12 intrinsic state into a series of lo wer-K stales. The half-life of the K = 12 state has been determined to be less than 2 ns and reduced hindrance factors have been calculated for each of the new decay transitions. In apparent conflict with the K -selection rule, most of these new decays have small reduced hindrance factors. The reasons for this apparent breakdown in the K-selection r ule are discussed in terms of a mixing between states of both low- and high-g. In addition the mean lifetimes of the states in four of the c ollective rotational bands have been determined using the Doppler shif t attenuation method. The deformations extracted from these measuremen ts are in good agreement with predictions from theoretical Total Routh ian Surface calculations based on the proposed configuration assignmen ts. (C) 1998 Elsevier Science B.V.