Nuclear-structure studies of Sr88 and Y89 by inelastic electron scattering

The nuclei Sr88 and Y89 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 Sr88 at 1.84 MeV (2+), 2.74 MeV (3-), 4.0, 6.5, and 7.8 MeV; and in Y89 at 1.50 MeV (32-), 1.73 MeV (52-), 2.21 MeV (52+), 2.52 MeV (72+), 2.86 MeV ((52, 72+), 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 Y89 cannot be described by a weak coupling of the 2p12 proton to core-excited states of Sr88. The sum of the B(E2)'s of the low-lying quadrupole states in Y89 is found to be about 30% of the B(E2) of the 1.84-MeV state of Sr88, and three strong octupole states are excited in Y89, 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.