Momentum-transfer dependence of S 2p excitations of sulfur hexafluoride by angle-resolved electron-energy-loss spectroscopy.

Abstract

Absolute generalized oscillator strengths (GOS's) of S 2p excitations of ${\mathrm{SF}}_{6}$ have been determined as a function of momentum transfer K, using angle-resolved electron-energy-loss spectroscopy at 2.5-keV impact energy. The GOS for the dipole-forbidden S 2p\ensuremath{\rightarrow}6${\mathit{t}}_{1\mathit{u}}$ transition was found to be significantly enhanced at large K, in contrast to the generally decreasing trend observed for the dipole-allowed discrete and shape-resonance states of the S 2p shell. A simple empirical analysis based upon the Lassettre series expansion showed that this state has a dominant quadrupole contribution.