K edge absorption spectra of sulphur in vapour, molecular and polymerized solid phases

X-ray K absorption spectra of sulphur have been studied in its vapour, molecular and polymerized solid phases. The vapour phase of sulphur containing molecules yields a K spectrum which is similar to that of the molecule. This observation suggests a ground state of , which is in agreement with that obtained from optical spectra. Different line splittings in the spectra of these molecules are discussed in the light of the p orbital and s - p orbital energy differences of some second- and third-period elements. While the condensed phase spectrum of remains unchanged, the observed K spectrum of condensed differs considerably from its vapour phase. This abrupt change in the bonding between the S atoms in the condensed phase is typical behaviour of sulphur and indicates the formation of two directional covalent bonds and creation of and lone pairs. This behaviour is, in fact, a clear distinction between the chemistries of sulphur and that of its homologue oxygen. The cyclic and chain forms of sulphur show some similarity in line structure and a marked difference in their near-edge structure due to a different number of S atoms surrounding a central atom in these allotropic forms.