VELOCITY ANALYSIS OF ELECTRONS SCATTERED BY MOLECULES IN THE PROCESS OF EXCITATION

Author Institution: Optics Division, U S. Naval Research Laboratory“When a beam of electrons strikes a gas sample, a certain portion of the electrons is scattered after having suffered an energy loss in the process of raising the gas molecules to higher energy levels. It is possible to separate the electrons undergoing various quantum losses by means of an electron, velocity analyzer and thereby study their individual scattering patterns. Several kinds of information are available from experiments of this sort. It is a simple matter to measure the energy losses involved in exciting molecules to their various quantum states. The total cross-section and the symmetry of a particular excited state associated with a given energy change can be determined. It is also theoretically possible and perhaps within experimental capabilities to obtain information concerning the electron distributions of atoms and molecules in their states of excitation. Experimental results have been obtained for a few molecules. One generally unexpected feature has been the appearance of maxima and minima in the patterns. It was believed that scattering involving energy changes would be incoherent and monotonically decreasing in intensity with increase in scattering angle. A general theory concerning this coherent, inelastic scattering has been developed.