Absolute Generalized-Oscillator-Strength Measurement of C 1 s Preionization-Edge Electronic Excitations of C₂F₆

Absolute generalized oscillator strengths (GOSs) for the C 1 s preionization-edge transitions at 295.4 eV and 297.7 eV in perfluoroethane have been determined as functions of energy loss and momentum transfer (K) at impact energy of 2.5 keV for the first time. The corresponding GOS profiles have been found to have the characteristic dipole-dominated shapes with a strong maximum at K = 0. The spectral features can be interpreted in terms of transitions terminating at the σ^* (C-F) molecular orbital.