The mechanism for photofragmentation of H2S revealed by multiphoton ionization photoelectron spectroscopy

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Abstract
Multiphoton ionization photoelectron measurements for H2S were carried out at several laser wavelengths in the 422–475 nm region, in order to obtain a direct evidence for the mechanism of ionic fragmentation which takes place by resonantly enhanced multiphoton ionization (REMPI). An ion current spectrum of multiphoton ioniztion was also measured for H2S in this wavelength region, indicating that the ionization takes place via three‐photon resonant Rydberg states. From photoelectron spectra obtained here, it has been found that the main peaks are attributed to the H2S+ ion in the ground state with v = 0. Other photoelectron bands due to v = 1 have also been observed together with some satellite bands. It should be mentioned that no photoelectron bands above 1.3 eV have been found. These experimental evidences directly support the parent ion fragmentation mechanism that the formation of HS+ and S+ ions mainly results from the ground state H2S+ ion with v = 0 and v = 1, respectively, by additional photon absorption. This conclusion differs from that recently suggested by Carney and Baer from their mass‐resolved REMPI experiments.