Angular distributions were measured for elastic and inelastic alpha-particle scattering by isotopically enriched targets of 116 Sn, 118 Sn, 120 Sn, and 122 Sn using the 40-MeV alpha beam of the NASA 60-inch cyclotron. Two states of energies close to 1.2 and 2.4 MeV were the only strong excitations observed. The inelastically scattered groups of alpha particles were analyzed using a distorted-wave Born approximation (DWBA) and the nuclear vibrational model. The results of these calculations are in good agreement with the known spins and parities: 2 + for the first excited state and 3~ for the second. DWBA calculations were also carried out for the 2 + excitations using eigenfunctions of the pairing plus Q-Q potentials. The calculated cross sections show a tendency to decrease with increasing neutron number. The experimental trend is qualitatively similar but much less regular. The absolute cross sections calculated using only cloud configurations are short of experimental values by about a factor of 4 when the Gammel-Thaler 40-MeV proton-alpha interaction is used. The relation of this discrepancy to the contribution from extracloud configurations is discussed.
a particles of 42-MeV energy were elastically and inelastically scattered from isotopically enriched targets of 113 In, 115 In, 107 Ag, 109 Ag, 121 Sb, and 123 Sb. Angular distributions were measured for a number of states in each isotope for angles between 30° and 80°. The results are compared with the predictions of the simple excitedcore model with respect to the strengths and energies of the excitations. In all six isotopes, states were found which accounted for all of the one-quadrupole-phonon vibrational strength observed in the neighboring even-even nuclei. In 113 In, 115 In, and 121 Sb, multiplets of states were seen which contained all of the strength of the octupole vibrational states of the even neighbors. In 107 Ag and 109 Ag, only half of the expected octupole strength was observed. In both silver isotopes, a number of states were seen which have approximately the proper strengths and excitation energies to arise from the coupling of the odd proton to a two-phonon vibrational state of the core.
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