Shape coexistence from the structure of the yrast band inPt174

Excited states in the very neutron-deficient nucleus ${}_{}{}^{174}{}_{}{}^{}\mathrm{Pt}$ have been identified up to spin 14. An irregular yrast sequence was observed beginning with a high $2^{+}$→$0^{+}$ energy. It can be interpreted as the result of a change from a weakly deformed ground-state band, to a well-deformed rotor, near spin 6.