Effect of π g9/2 and vg9/2 alignments in the shape of 75Br from lifetime measurement

Lifetimes of 18 high spin states of Br-75 were measured by Doppler shift attenuation method. The high spin states in the nucleus were populated by the reaction V-51(Si-28, 2p2n) at 115 MeV beam energy. The transition quadrupole moments, deduced from the lifetimes, were measured beyond the g(9/2) neutron and proton band crossings in the positive and the negative parity bands. The results were discussed in the cranking model with Woods-Saxon potential and Strutinsky shell correction. Change in triaxiality gamma due to neutron and proton alignments has been proposed to explain the observed change in transitional quadrupole moments Q(1). The experimental results and the cranking calculations suggest that the alignment of a pair of neutrons in the 99/2 orbital tends to drive the shape of the nucleus towards negative value of gamma while the proton pair alignment in the 99/2 orbital tends to drive it towards positive gamma. (C) 2009 Elsevier B.V. All rights reserved.