Polarisation of radiation from H2excited by electron impact Lyman and Werner emissions and Lyman-α

The polarisation of selected Lyman and Werner bands and also of Lyman- alpha radiation are measured as a function of impact electron energy in the range from threshold to 300 eV. Polarisations in excess of 0.2 are obtained in certain instances. The results for Lyman- alpha confirm and extend those of Ott et al. (1970). Extrapolations of the results to the thresholds are compared with estimates based on angular-momentum conservation and symmetry arguments. For the Werner emission a further comparison is made with a 'pseudo'-threshold polarisation measurement using the scattered-electron-delayed-photon coincidence technique. The apparent excitation functions for the two molecular emissions are derived from the measurements of polarisation. In both cases good agreement is obtained with the semi-empirical data of Gerhart (1975). Comparison is made with the results of other workers wherever possible.