Delayed backbending in the pi h(9/2) band of Ir-187

Abstract

High-spin states of Ir-187 have been populated in the Yb-176(N-15,4n) reaction and measured with the YRAST Ball spectrometer. The pih(9/2) rotational band has been extended beyond the first alignment crossing, which was found at rotational frequency (h) over bar omega(c) approximate to0.39 MeV . Two different scenarios for describing this crossing are considered: the alignment of an h(9/2) proton or i(13/2) neutron pair and it is concluded that a proton band crossing is more likely. A systematic study of the rotational alignment crossings in the pih(9/2) bands in the N=104,106,108 isotopes of Ta-73,Re-75,Ir-77, and Au-79 is presented.