States built on the 9/2(+) isomers in Y-91,Y-93

Publication Type
Journal Article
Year of Publication
Fotiades, N.
Cizewski, J. A.
Krucken, R.
Clark, R. M.
Fallon, P.
Lee, I. Y.
Macchiavelli, A. O.
Younes, W.
Name of Publication
European Physical Journal A
Date Published
Short Title
States built on the 9/2(+) isomers in Y-91,Y-93
Accession Number
ISBN Number

The isotopes Y-91,Y-93 are located close to Zr-90, a nucleus that has a neutron shell closure (N = 50) and a proton subshell closure (Z = 40), and close to the stability line. However, relatively little is known about excitations above their 9/2(+) isomers. In the present work the isotopes Y-91,Y-93 have been studied in the fission of compound systems formed in two heavy-ion-induced reactions using the Gammasphere array for gamma-ray spectroscopy. States with excitation energies up to 6.9 and 7.1MeV above the previously known 9/2(+) isomers of Y-91,Y-93 were established, respectively. The coupling of a proton-hole occupying the g(9/2) orbital to the yrast states in the core nuclei of Sr-90 and Zr-92 can account for the first excited states of Y-91. A comparison with the first excited states in the neighboring N = 52, 54 isotopes is also considered. The experimental results are compared to predictions from previously reported shell-model calculations. The present results enhance previous knowledge on Y-91,Y-93 from fusion-evaporation reactions and multinucleon transfer reactions, and highlight the roles of these complementary reactions in probing moderate spin excitations in this mass region.