Polarisation of the 63P1-61S0line of Hg

The polarisation of the 6 3 P 1 -6 1 S 0 line of Hg after excitation of the 6 3 P 1 state by electrons scattered in the forward direction is evaluated as a function of electron energy using cross sections based on the Born-Ochkur approximation. Good accordance is obtained with the recent experimental data of Hanne et al. In particular, the theory yields the value 7.1 eV for the incident electron energy where the polarisation vanishes, which is close to the value predicted by the experimental study. Moreover this energy should be independent of the isotope of Hg.