Electronic properties of the SF5Cl molecule: a comparison with SF6. I. Photoabsorption spectra near the sulphur K and chlorine K edges

Abstract The X-ray photoabsroption spectrum of the gas phase SF 3 Cl molecule has been recorded with synchroton radiation in the 2450–3100 eV region, i.e. near the sulphur and chlorine K edges. Results are analysed on the basis of a detailed comparison with the sulphur K spectrum of SF 6 and multi reference configuration interaction calculations on the core equivalent molecule of SF 6 and SF 5 Cl. We interpret the resonances located below the SK ionization onset, in terms of one electron (core→ valence of Rydberg) transitions and we show the effects of the breaking of symmetry from SF 6 to SF 5 Cl. We clarify the role played by the d orbitals i.e. we reject the concept of spd hybridization and we show that d orbitals had a true Rydberg character. We also predict using the same calculations that bound doubly excited states exist below the sulphur K edge of SF 5 Cl very close in energy to the main resonances. In the continuum, which includes near edge resonances and EXAFS oscillations, we observed a striking resemblance between the two molecules. The chlorine atom is shown to have a weak effect on the multiple scattering resonance because they are dominated by the fluorine cage effect. The presence of autoionizing doubly excited states with an abnormal intensity is discussed.

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