Abstract:

States of 89Y, populated through the 87Rb(α, 2n) reaction in the energy range Eα = 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- ⊗ g9 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. © 1978.