Emergence of principal axis rotation in 110Ag

The negative-parity yrast band of 110Ag has been extended significantly and the lifetimes of the high spin levels of this band have been measured. The experimentally observed level scheme and measured electromagnetic transition rates have been compared with the theoretical predictions of a model with two quasiparticles coupled to a triaxially deformed core. This calculation successfully reproduces the energy spectra and electromagnetic transition rates beyond Iπ=12-ℏ. These observations indicate that the principal axis of rotation is responsible for the generation of high angular momentum states along the yrast cascade in 110Ag. In all the other lighter isotopes, these states are generated through titled axis rotation. Thus, 110Ag is the first nucleus where the boundary between tilted and principal axis rotation could be established.