Principles and procedures for determining absolute differential electron-molecule (atom) scattering cross sections

Abstract

A set of procedures for measuring the absolute elastic and inelastic differential cross sections (DCS) for electronimpact on molecular (atomic) species is described. First the elastic DCS of a test gas is obtained using a relative flow technique which measures the elastic DCS of the test gas in terms of that of helium at each impact energy and angle. Then the inelastic DCS is obtained in terms of the elastic DCS at each impact energy and angle by means of an energy-loss spectrum, corrected for background scattering, containing both elastic and inelastic features. To relate the amplitudes of the inelastic features in the energy-loss spectrum to the amplitude of the elastic peak, it is necessary to know the energy response function of the detector. A procedure for measuring this energy response function is given. The problem of extracting inelastic DCS information from complicated molecular spectra with overlapping inelastic features is discussed.