Valence electronic excitation of the SiF4 molecule: generalized oscillatorstrength for the 5t(2)-> 6a(1) transition and ab initio calculation

The electronic excitation of the silicon tetrafluoride (SiF4) molecule has been studied using the angle-resolved electron energy-loss technique, at 1. 0 keV incident electron energy, in the 0-50 eV energy range with an angular range of 1.5 degrees -20.0 degrees. The absolute generalized oscillator st rength (GOS) for the 5t(2) --> 6a(1) electronic transition, located at 13.0 eV, has been determined. A minimum has been observed in the GOS for this t ransition at K-2 = 1.4 au. We have also determined the absolute elastic and inelastic differential cross sections at I keV. In order to help in the in terpretation of the experimental results, ab initio calculations have been performed for the vertical valence transitions and ionization energies for the SiF4 molecule. Configuration-interaction calculations, including single and double excitations (CI-SD) and the symmetry-adapted-cluster expansion (SAC) were used. The CI-SD approach was also employed to obtain the optical oscillator strength for the 5t(2) --> 6a(1) transition.