SYMMETRY SELECTION-RULES FOR VIBRATIONAL-EXCITATION BY RESONANT ELECTRON-IMPACT AND A UNIFIED TREATMENT OF VIBRONIC COUPLING BETWEEN RESONANCES AND TO THE CONTINUUM - A COMPLETE SYMMETRY ANALYSIS OF VIBRATIONAL-EXCITATION IN BENZENE

A symmetry analysis of the contributions to the transition operator from vibronic coupling provides symmetry selection rules for vibrational excitation by resonant electron impact in polyatomic molecules. In the context of electron scattering vibronic coupling operates in two modes. These are named internal and external vibronic coupling. Internal vibronic coupling operates within and among the quasibound states giving rise to the resonances. External vibronic coupling operates between the quasibound states and the continuum. We discuss the differences, particularly with respect to the angular distribution of electron scattering. A complete symmetry analysis of vibrational excitation is given using benzene as an example.