ELECTRON-PHOTON ANGULAR-CORRELATION IN ATOMIC PHYSICS

A review is given on recent developments of electron-photon angular correlations resulting from electron impact of atoms and molecules. After a description of experimental methods the theory of measurement of electron-photon angular correlations is outlined in the following way. By applying measurements of electron-photon angular correlations a sub-ensemble of excited atoms is selected from the atomic target which can be characterized by special properties of the atomic state. These special target properties are the various orientation and alignment parameters and the multipole moments of the excited state. General considerations are concerned with the description by Stokes parameters of coincident photons, coherence effects in impact excitation, and the influence of fine and hyperfine interactions and quantum beats in angulat correlations. The formulation presented here is a general one which can also be applied, for example, to an analysis of light emitted by beam foil excited hydrogenic levels. The relationship between scattering amplitudes (including their phases) and target parameters (orientation and alighment und multipole moments) is worked out for singlet-singlet and non-singlet transitions. Comparison is made between numerical calculations and experimental data from electron-photon coincidence experiments. © 1979.