High-spin structure of the spherical nucleus 90Y -: art. no. 044327

High-spin states in Y-90 were populated in the Se-82(B-11,3n) reaction at a beam energy of 37 MeV. gamma rays were detected with the spectrometer GASP. The level scheme of Y-90 was extended up to J(pi)=(18(+)) at 9.6 MeV. Mean lifetimes of four levels were determined using the Doppler-shift-attenuation method. The structure of Y-90 was interpreted in terms of the shell model. The calculations were performed in the model space pi(0f(5/2),1p(3/2),1p(1/2),0g(9/2)) nu(1p(1/2),0g(9/2),1d(5/2)) and in an extended space including the nu(0g(7/2)) orbital also. The calculations in the extended model space reveal a correspondence between states in Y-90 and Y-89. Moreover, a combination of the predicted states with J(pi)greater than or equal to14((+)) can be found that reproduces the large experimental B(M1) values of up to about 1 Weisskopf unit.