Excitation of thallium and lead atoms by electrons in the relativistic distorted-wave approximation

Relativistic distorted-wave calculations are reported for the differential cross section and a complete set of S, T and U parameters for electron impa ct excitation of thallium from its ground state 6p P-2(1/2) to the fine-str ucture state 6p P-2(3/2) as well as the 7s S-2(1/2) state, and of lead for the fine-structure transitions Po-3 --> P-3(1), P-3(2) and D-1(2). Our resu lts for the asymmetry parameter S-A are compared with the only available ex perimental measurements from the Munster group and the agreement is very sa tisfactory.