Observation of new multipole electronic transitions in chlorofluoromethanes: Generalized oscillator strength measurements by angle-resolved electron energy loss spectroscopy

Non-dipole electronic transitions in 7-10 eV have been observed in a series of chlorofluoromethanes, CF4-nCln (n=1-3), using angle-resolved electron energy loss spectroscopy at 2.5 keV impact energy. The generalized oscillator strengths of these low-lying non-Rydberg transitions have been determined and found to have a shape characteristic of a quadrupole-allowed transition. Ab-initio single-excitation CI calculations show that some of these quadrupole states correspond to predissociation channels due to the breakage of the C-Cl bond. Some plausible spectral assignments and related processes of these non-dipole transitions will be discussed. Furthermore, the GOS measurement of Cl 2p and Cls transitions also gives evidence for the presence of non-dipole processes in the inner shells