On the Origin of 21/2 Yrast Trap in Mo

Isomerism of the high-spin yrast 21/2 states of the N =51 isotones Zr, Mo and Ru has been investigated using the shell model calculations. It is found that the low-j πp1/2 is responsible for the only yrast trap in Mo. In addition, the relatively smaller 10+1 -12 + 1 level spacing in Mo has been found by investigating the systematics of the 10+1 -12 + 1 level structures in the N =52 isotones Zr, Mo and Ru. This result provides a supplementary argument to the origin of the 21/2 yrast trap in Mo from the viewpoint of the similarity between the configurations of 10+1 -12 + 1 states in Mo and those of 17/2+1 -21/2 + 1 states in Mo.