High-spin states in the semimagic nucleusY89and neutron-core excitations in theN=50isotones

Abstract

The semimagic nucleus $^{89}\mathrm{Y}$ has been investigated using the $^{82}\mathrm{Se}(^{11}\mathrm{B},4n)$ reaction at beam energies of 48 and 52 MeV. More than 24 new transitions have been identified, leading to a considerable extension of the level structures of $^{89}\mathrm{Y}$. The experimental results are compared with the large-basis shell model calculations. They show that cross-shell neutron excitations play a pivotal role in high-spin level structures of $^{89}\mathrm{Y}$. The systematic features of neutron-core excitations in the $N=50$ isotones are also discussed.