High-spin states and lifetime measurements in [formula omitted]Hf

Abstract

This paper describes the results of two complementary experiments which studied the properties of the well-deformed nucleus 171 Hf. The first experiment, with a thin self-supporting target, extended the rotational bands built upon the [633]7 /2, [512]5 /2 and [521]1 /2 configurations up to spins of 73 /2–85 /2ℏ. The configurations of these bands and observed band crossings are discussed within the framework of the cranked-shell model. The second experiment employed a backed target in order to measure the lifetimes, by the Doppler Shift Attenuation method, and thereby establish deformations for some of the states in the collective rotational bands. The extracted deformations are found to be consistent with those predicted from theoretical Total Routhian Surface calculations. These deformations provide strong evidence that the high-spin states in 171 Hf, and perhaps more importantly, in the region where the high- K ( K π=19/2 + and K π=23/2 − ) isomeric states decay, retain their well-deformed axial symmetry.