An experimental and theoretical study of the valence shell photoelectron spectrum of sulphur hexafluoride Original Research Article

The complete valence shell photoelectron spectrum of sulphur hexafluoride has been studied using HeII and synchrotron radiation. The high resolution HeII excited spectrum has allowed a detailed analysis to be made of the vibrational structure exhibited in the photoelectron bands associated with ionisation from the outer valence orbitals. New vibrational structure has been observed in the C 2Eg and the F2A1g photoelectron bands. The spectra recorded with synchrotron radiation demonstrate that shape resonance phenomena affect the photoionisation dynamics, and clear evidence is provided for both the t2g and the eg shape resonances. However, the results show that photoelectrons associated with gerade symmetry orbitals also exhibit resonant behaviour, and this is discussed in terms of interchannel coupling and the possibility that the t1u shape resonance might occur above threshold for valence shell ionisation. An essentially structureless photoelectron intensity distribution is observed throughout the entire region for binding energies greater than 25 eV, and this suggests a strong coupling to continuum states. A perturbative Greenʹs function method has been employed to evaluate the ionisation energies and pole strengths associated with the six outermost molecular orbitals, and the results show an improved agreement with the experimental values.