AN EXPERIMENTAL AND THEORETICAL-STUDY OF THE VALENCE SHELL PHOTOELECTRON-SPECTRUM OF SULFUR-HEXAFLUORIDE

The complete Valence shell photoelectron spectrum of sulphur hexafluor ide has been studied using HeII and synchrotron radiation. The high re solution HeII excited spectrum has allowed a detailed analysis to be m ade of the vibrational structure exhibited in the photoelectron bands associated with ionisation from the outer valence orbitals. New vibrat ional structure has been observed in the C (2)E(g) and the F(2)A(1g) p hotoelectron bands. The spectra recorded with synchrotron radiation de monstrate that shape resonance phenomena affect the photoionisation dy namics, and clear evidence is provided for both the t(2g) and the e(g) shape resonances. However, the results show that photoelectrons assoc iated with gerade symmetry orbitals also exhibit resonant behaviour, a nd this is discussed in terms of interchannel coupling and the possibi lity that the t(1u) shape resonance might occur above threshold for va lence shell ionisation. An essentially structureless photoelectron int ensity distribution is observed throughout the entire region for bindi ng energies greater than 25 eV, and this suggests a strong coupling to continuum states. A perturbative Green's function method has been emp loyed to evaluate the ionisation energies and pole strengths associate d with the six outermost molecular orbitals, and the results show an i mproved agreement with the experimental values.