Cross section for Ly-α emission by electron impact on methane

Utilizing Ly-α emission cross sections for H2 as secondary standards, absolute values of Ly-α emission cross sections for CH4 have been obtained for electron impact energies varying from the threshold to 100 eV. A crossed electron beam-molecular beam geometry was employed and the Ly-α radiation was detected at 900 and 450 with respect to the incident electron beam by a solar blind photomultiplier in tandem with an oxygen filter. The results are compared with previous measurements. Appreciable differences among the various experimental data are found. (orig.)