High-spin states and shape change in 81Sr

High-spin states have been studied in 81Sr using the 56Fe(28Si, 2pnγ)81Sr reaction at laboratory energies of 103.5 and 108 MeV. γ-γ coincidence and γ-ray angular distribution measurements were performed. New states were found at 5353 [(29/2)+], 5999 [(31/2)+], 6750 [(33/2)+], 2448 [(17/2)-], 2906 [((19/2)-)], 3495 [((21/2)-)], and 3980 [((23/2)-)]. A shape change was seen in the yrast band at the (29/2)+ state. Below this level, the band exhibits strong signature splitting and predominant E2 decays. Above it lies a band with almost no signature splitting and predominant M1 decays. The yrare negative parity band shows almost no signature splitting and continues smoothly up to spin (23/2)-. The moments of inertia of the positive and negative parity bands are almost the same and increase with spin in a roughly parallel fashion