LOW-LYING LEVELS OF 208PB WITH G9/2, I11/2, OR J15/2 NEUTRON-PARTICLE CONFIGURATIONS

The low-lying states of Pb208 which have a neutron configuration (g92, j-1) are studied in proton scattering at the resonance energy for the g92(g.s.) single-neutron isobaric-analog resonance (IAR) in Bi209. The onresonance proton angular distributions are taken from 15°to 170°for states between 3.0- and 4.5-MeV excitation in Pb208, and are found to be nearly symmetric about 90°except for the lowest 5- (3.192-MeV) state. Total proton inelastic scattering cross sections and proton partial widths are obtained from the angular distributions. The states in the energy ranges 3.0-3.8, 3.8-4.15, and 4.15-4.8 MeV in Pb208 are found to have the dominant neutron-neutron-hole configurations of (g92, p12-1), (g92, f52-1), and (g92, p32-1), respectively. Some tentative spin assignments based on the partial widths, excitation energy, and angular distributions of the states are given. Two previously unreported states at 3.940 and 4.376 MeV in Pb208 are observed in the high-resolution (p, p) spectrograph data, and the levels previously reported at 4.032 and 4.252 MeV are observed to be doublets with 12- and 6-keV energy separations, respectively. The cross sections were also measured for the (p, p) reaction at the g92 resonance at 20°, 40°. 60°, and 90°for 24 states between 4.6- and 6.00-MeV excitation. In addition to the g92 resonance, the i112 (0.79-MeV) IAR and j152(1.42-MeV)IAR are studied, and the observed states are compared with those observed in the Pb207(d,p) reaction. Partial widths for all the states between 2.0- and 4.5-MeV excitation containing g92 neutron strength are calculated using the theoretical shell-model wave functions of Kuo and Brown and of Pinkston and True, and are compared with the experimentally observed widths. © 1969 The American Physical Society.