Electron energy-loss spectra (EELS) of SF6 have been recorded in the region of S 2p, S 2s, and F ls excitation, using both dipole and nondipole electron-scattering conditions. Impact energies between 700 and 3200 eV and scattering angles between Oº and 30º were used. Relative to dipole EELS or photoabsorption, there are large intensity redistributions in both the S 2p and S 2s s spectra under nondipole conditions. In contrast, the F ls spectrum is essentially the same in near-dipole and nondipole scattering regimes. A higher order electric multiple S 2p spectra feature is observed at 181 eV. It has an unusual multipeaked line shape whose components are more closely spaced than the typical 1.15-eV S 2p spin-orbit splitting. It is attributed to the overlap of several quadrupole-coupled states, which are likely associated with the [S 2p(tlu)-I,tlu] configuration. Ab initio self-consistent field calculations for various open-shell S 2p excited states are used to assist spectral assignments.
©1995 The American Physical Society