Nuclear-Structure Studies ofSr88andY89by Inelastic Electron Scattering

Abstract

The nuclei ${\mathrm{Sr}}^{88}$ and ${\mathrm{Y}}^{89}$ have been studied by observing the inelastic scattering of 65- and 70-MeV electrons through angles 70°-150°, with an over-all energy resolution of 200 keV. Strongly excited states were found in ${\mathrm{Sr}}^{88}$ at 1.84 MeV ($2^{+}$), 2.74 MeV ($3^{-}$), 4.0, 6.5, and 7.8 MeV; and in ${\mathrm{Y}}^{89}$ at 1.50 MeV (${\frac{3}{2}}^{-}$), 1.73 MeV (${\frac{5}{2}}^{-}$), 2.21 MeV (${\frac{5}{2}}^{+}$), 2.52 MeV (${\frac{7}{2}}^{+}$), 2.86 MeV (($\frac{5}{2}, {\frac{7}{2}}^{+}$), 3.1, 3.72, 4.0, and 4.16 MeV. The data were analyzed by a distorted-wave calculation to determine multipolarities and reduced nuclear radiative transition probabilities. The results show that the excited states in ${\mathrm{Y}}^{89}$ cannot be described by a weak coupling of the $2p_{\frac{1}{2}}$ proton to core-excited states of ${\mathrm{Sr}}^{88}$. The sum of the $B\left(E2\mathrm{}\right)\text{'}\mathrm{s}$ of the low-lying quadrupole states in ${\mathrm{Y}}^{89}$ is found to be about 30% of the $B\left(E2\mathrm{}\right)\mathrm{}$ of the 1.84-MeV state of ${\mathrm{Sr}}^{88}$, and three strong octupole states are excited in ${\mathrm{Y}}^{89}$, where only two are expected from the weak-coupling model. No detailed information on the single-particle structure of the levels could be obtained at these momentum transfers.