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 su lfide, and D,S, deuterium sulfide, at the sulfur L(2,3) ionization thr esholds has been measured using synchrotron radiation with high-energy ; resolution from the SX700/II soft-x-ray monochromator at the Berline r 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 abov e the L, threshold energy, broad valence-shell absorption features 5-8 eV below the L, edge, and many narrower Rydberg:excitations 0-5 eV be low the L, edge, Comparison of the H,S and D,S spectra allows the iden tification,of transitions which include vibrational excitation, due to the isotopic dependence of vibrational energies; For the (2p)(-1) cor e-excited Rydberg states, a least-squares analysis was employed, which deconvoluted the core-level and excited-orbital splittings. Results s how that the twofold degeneracy of the sulfur 2p(3/2) core level is re moved by the molecular field, with a resulting splitting of 115 meV fo r the higher-energy-core-excited Rydberg states. The energies of the h igher Rydberg states were well described by the Rydberg formula with t he quantum defects delta(p) = 1.63 and delta(d) = 0.32. Fine structure was resolved in the transitions to the dissociative (2p)(-1) core-exc ited valence-shell states. The regular spacing and isotopic dependence of this structure clearly identifies it as a vibrational progression.