Energy inversion of thef7/2 andh9/2 neutrons in yrast states of154Yb

The N=84 nucleus154Yb was investigated through the106Cd(54Fe,α2p) reaction. We found the 16+ yrast level in this nucleus to be formed by the (πh11/22νf7/2h9/2) configuration, in contrast to the lower-Z isotones where (πh11/22νf7/22)16+ is the yrast state. Manybody shell model calculations with empirical two-body interactions support our conclusion.