Abstract
The light polarisation for the optical transitions 82S1/2-62P1/2,3/2 and 62P3/2-62S1/2 in caesium after impact excitation by polarised electrons has been measured from the thresholds to 10 eV (82S1/2 excitation) and 80 eV (62P3/2 excitation). From the data the relative contribution of exchange can be determined. This relative contribution does not differ significantly for the electron impact excitation of the 62P3/2 state, which is an optically allowed transition, and the 82S1/2 state, which is an optically forbidden transition. In the range of overlap, the authors' data show fair agreement with experimental and theoretical data from other authors.