HIGH-RESOLUTION PHOTOABSORPTION NEAR THE SULFUR L(2,3) THRESHOLDS - H2S AND D2S

The x-ray-absorption near-edge stricture of gas-phase H2S, hydrogen sulfide, and D,S, deuterium sulfide, at the sulfur L(2,3) ionization thresholds has been measured using synchrotron radiation with high-energy; resolution from the SX700/II soft-x-ray monochromator at the Berliner Elektronenspeicherring-Gessellschaft fur Synchrotronstrahlung m.b.H. Previously unobserved fine structure is resolved. The spectra of both molecules are characterized by multielectron excitations 8-14 ev above the L, threshold energy, broad valence-shell absorption features 5-8 eV below the L, edge, and many narrower Rydberg:excitations 0-5 eV below the L, edge, Comparison of the H,S and D,S spectra allows the identification,of transitions which include vibrational excitation, due to the isotopic dependence of vibrational energies; For the (2p)(-1) core-excited Rydberg states, a least-squares analysis was employed, which deconvoluted the core-level and excited-orbital splittings. Results show that the twofold degeneracy of the sulfur 2p(3/2) core level is removed by the molecular field, with a resulting splitting of 115 meV for the higher-energy-core-excited Rydberg states. The energies of the higher Rydberg states were well described by the Rydberg formula with the quantum defects delta(p) = 1.63 and delta(d) = 0.32. Fine structure was resolved in the transitions to the dissociative (2p)(-1) core-excited valence-shell states. The regular spacing and isotopic dependence of this structure clearly identifies it as a vibrational progression.