Vibrational effects on electronic transitions in molecules studied by (e,2e) electron momentum spectroscopy and EELS

摘要

Coupling between electronic and nuclear motions in molecules is of great importance for many physical and chemical processes. For instance, the appearance of dipole-forbidden lines in optical spectra has generally been attributed to the distortion of electronic wave functions caused by molecular vibration. Electron momentum spectroscopy (EMS) provides a powerful means for investigating vibrational effects on electronic wave functions [1] because of its unique ability to look at individual molecular orbitals in momentum space. Furthermore, we have recently shown that electron energy loss spectroscopy (EELS) is a useful method to assess vibrational effects on electronic excitation processes [2, 3]. In this contribution, we report our recent EMS and EELS studies of vibrational effects on electronic transitions in molecules.