High spin states in 89Y

Abstract

States of 89Y, populated through the 87Rb(α, 2n) reaction in the energy range E α = 30 to 55 MeV. were studied using in-beam γ-ray spectroscopy techniques. Excitation functions, γ-ray angular distributions and γ-γ coincidences were measured. Nine hitherto unknown states above 3.3 MeV were found and their decay modes were determined. These levels are tentatively assigned spin values from I = 13 2 up to 23 2 . Their energies are found to be close to those obtained from coupling the 3 −, (5) −, (6) − and(7) − states of the 88Sr core with the single-particle 9 2 + isomeric state at 908.8 keV. The validity of a weak coupling description for these high spin states is further supported by the similarites with the known 87Sr data. The analogy with 87Sr seems however to breakdown regarding the I = 15 2 highest spin member of the {3 − ⊗ g 9 2 } multiplet. This state appears to lie significantly higher in 89Y. The data confirm the previous information existing on levels below 3.3 MeV, with the exception of a level found at 2894.3 keV and for which a tentative I = 13 2 + assignment is proposed.