The 206Pb( t, p) 208Pb and 210Pb( p, t) 208Pb reactions at 20 MeV

Abstract

The 206Pb( t, p) 208Pb and 210Pb( p, t) 208Pb reactions have been studied at 20 MeV up to an excitation of 6.75 MeV in the ( p, t) reaction and up to 8.5 MeV in the ( t, p) reaction. Angular distributions of 10°-80° are observed in both reactions. The spin and parity of about thirty states have been tentatively identified from their angular distribution patterns and by comparison of the cross sections measured in the ( p, t), ( t, p), ( p, p′), and ( d, p) reactions. Pairing-vibrational states (0 +) and 2 +) are identified and the presence of a proton pairing vibrational state (0 +) at 5.24 MeV is suggested by the data. Two-neutron transfer DWBA cross sections were calculated for about 50 states using one-particle, one-hole wavefunctions calculated by Kuo. These wavefunctions were characterized by having appreciable parentage in the valence neutron particle (hole) configurations of 210Pb( 206Pb). Tentative identification with observed states allows a quantitative comparison. The strongly populated pairing-vibrational states are compared with DWBA calculations using the valence neutron wavefunctions of True and Ford, and Redlich for 206 Pb and 210Pb. Discrepancies are discussed in terms of mixing with the analogs of higher lying 2 + states in 210Pb and in terms of the two-particle, two-hole wavefunctions.