Dracoulis, G. D.Bark, R. A.Stuchbery, A. E.Byrne, A. P.Baxter, A. M.Riess, F.2025-12-312025-12-310375-9474ORCID:/0000-0002-0198-9901/work/165470980https://hdl.handle.net/1885/733798061Excited states in the neutron-deficient nucleus 170Os were identified up to spin (24+) in the yrast band and to spin (23-) in the lowest negative-parity band. Deformation systematics implied by the 2+ state energies for the very light osmium isotopes are compared with theory. Band-crossing frequencies, alignments and alignment gains are compared with cranked shell-model calculations. Deformation changes are required to obtain detailed agreement. A three-band mixing approach is invoked to explain the low-spin yrast anomaly in 172Os and to reproduce the yrast band in 170Os. The excitation energy of the postulated "intruder" band in 170Os and 172Os is deduced.15enNUCLEAR REACTIONS198810.1016/0375-9474(88)90244-80000591592