DOUBLE CORE EXCITATION AT THE SULFUR K EDGE IN H2S, SO2 AND SF6

We report an experimental and theoretical study of the double-core exc itation processes in some sulfur-containing molecules in the gas phase . Absolute X-ray absorption cross-section of H2S, SO2 and SF6 have bee n measured in the 2400-2800 eV region. Several narrow features are obs erved some 200 eV above the edge and assigned to 1s2p double core exci ted states. The spectra depend upon atomic effects but also on the bon ding partner of the sulfur atom. The detailed assignment of resonances of H2S is made using calculations performed on the Z+2 core equivalen t species ArH2 and can be understood by analogy with the excited state s of the ArH+H system. Interpretation of the SO2 and SF6 spectra are m ade by combining atomic and molecular effects.