MIXED G-STATES IN HELIUM OBSERVED BY ELECTRON IMPACT EXCITATION OF THE TRIPLET-3D AND TRIPLET-4D LEVELS

Excitation of the 3('3)D and 4('3)D levels of helium by electron impact has been studied by time resolved spectroscopy to determine the relative intensities of cascade components. Absolute cross sections of the cascade components have been determined by normalizing to the measured absolute cross sections of Showalter and Kay (1975). The measured 4('3)F, 5('3)F, 6('3)F, and 5('3)G cascade components were then compared to the mixed F and G state models of van den Eynde et al (1972), Parish and Mires (1971), and the unmixed F state model. A new experimental value for the mixing coefficient (omega)(,n) has been determined. The cross section for the excitation of the mixed G states was found to be much larger than has previously been suggested.