One- and two-step processes in natural- and unnatural-parity 208Pb(p vector,t)206Pb reaction at Ep=22MeV

Reaction mechanism and nuclear-structure dependence of the natural- and unnatural-parity 208Pb(p,t)206Pb(2+,3+,4+,5- and 7-) reaction are studied by using a 22 MeV polarized proton beam. Angular distribution of the analyzing power for the second 3+(32+) transition has an opposite sign to that for the 3l+ one and the difference is explained in terms of the j-dependence in the sequential two-step (p,d)(d,t) process. The observed analyzing powers and cross sections for the two 3+ transitions are reproduced by the finite-range first- and second-order DWBA calculation. Two-step analysis is necessary to explain the variety of angular distributions of the analyzing powers for the natural-parity transitions. Microscopic analysis in terms of the one- and two-step (p,t) calculation is made for the transitions to the 2+1-5, 4+1-3, 5-1,2 and 71- states in 206Pb. The calculation reproduces the absolute values of the observed cross sections within a factor of 2. (orig.)