Investigations of Properties of 89Y Levels with Reactor Fast Neutrons

By employing a beam of reactor fast neutrons, the spectrum of gamma rays up to an energy of 4.6MeV and their angular distributions with respect to the neutron-beamaxis aremeasured in the reaction 89 Y( n , n 'γ). The multipolarities and multipole-mixture parameters for 34 gamma transitions and the spin–parities J π of states excited in this reaction are determined. The lifetimes of the lowest 32 levels of 89Y were measured by the Doppler shift attenuation method, and the reduced probabilities for the respective gamma transitions were calculated. Levels of the K π = +5/2 + and K π = −7/2 + bands associated with, respectively, prolate and oblate deformation shapes are found in 89 Y at low excitation energies.