Fluorescence emission from photo-fragments after resonant S 2p excitations in H2S

Abstract

Visible-UV fluorescence emission of gas-phase hydrogen sulfide, H₂S, has been studied at the S 2p edge with synchrotron radiation excitation. Dispersed fluorescence measurements in the wavelength range 300–900 nm were taken at several photon energies corresponding to the excitations of the S 2p electrons to the unoccupied molecular and Rydberg orbitals. The spectra reveal fluorescence from the H, S, S⁺, HS and HS⁺ photo-fragments. H is found to be the strongest emitter at Rydberg excitations, while the emission from S⁺ is dominant at the molecular resonances and above the S 2p ionization thresholds. The intensities of hydrogen Lyman-α (122 nm), Balmer-α (656 nm), Balmer-β (486 nm) transitions as well as the visible-UV total fluorescence yield (300–900 nm) and the total ion yield were measured by scanning the photon energy in small steps across the S 2p edge. The different Balmer lines show some sensitivity to the specific core excitations, which is, however, not so strong as that recently observed in the water molecule [E. Melero García, A. Kivimäki, L. G. M. Pettersson, J. Álvarez Ruiz, M. Coreno, M. de Simone, R. Richter and K. C. Prince, Phys. Rev. Lett., 2006, 96, 063003].