Spin Assignments From The Ba-138(Li-7,He-6)La-139 And Ce-140(Li-7,He-6)Pr-141 Reactions At 52 Mev

Abstract Angular distributions have been measured for transitions to low-lying states in 139La and 141Pr populated by the 138Ba(7Li, 6He)139La and the 140Ce(7Li, 6He)141Pr reactions at E7Li = 52 MeV. Elastic scattering of '7Li at 52 MeV on 138Ba and 140Ce, and 6Li at 48 MeV on '139La and at 47 MeV on 141Pr were measured. Optical-model parameters extracted from fits to the scattering data were used in a finite-range DWBA analysis of the angular distributions for levels below 2.40 MeV excitation energy in 139La and 1.65 MeV in 141Pr. Final-state spins have been assigned to levels in139La at 1.56 MeV ( 5 2 + ), 1.85 MeV ( 3 2 + ) and 1.96 MeV ( 3 2 + ) , and to the level in 141 ( 1 2 + ). The reaction cross sections exhibit less structure than predicted by the DWBA calculations, but the extracted spectroscopic factors are generally in good agreement with light-ion results.