K EDGE ABSORPTION-SPECTRA OF SULFUR IN VAPOR, 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 c ontaining S-2 molecules yields a K spectrum which is similar to that o f the O-2 molecule. This observation suggests a (3) Sigma(g)(-) ground state of S-2, which is in agreement with that obtained from optical s pectra. Different line splittings in the spectra of these molecules ar e discussed in the light of the p orbital and s-p orbital energy diffe rences of some second- and third-period elements. While the condensed phase spectrum of O-2 remains unchanged, the observed K spectrum of co ndensed S-2 differs considerably from its vapour phase. This abrupt ch ange in the bonding between the S atoms in the condensed phase is typi cal behaviour of sulphur and indicates the formation of two directiona l covalent bonds and creation of 3s(2) and 3p(2) lone pairs. This beha viour is, in fact, a clear distinction between the chemistries of sulp hur and that of its homologue oxygen. The cyclic and chain forms of su lphur show some similarity in sigma line structure and a marked diffe rence in their near-edge structure due to a different number of S atom s surrounding a central atom in these allotropic forms.