High-resolution studies of the electronic spectra of H2S and D2S

Abstract

The complementary techniques of high-resolution vacuum ultraviolet absorption spectroscopy and resonance-enhanced multiphoton ionisation spectroscopy have been employed in a reinvestigation of the vertical electronic spectra of the molecules H2S and D2S. In accord with previous, lower-resolution, absorption studies of H2S the major part of the spectra of both isotopic species may be understood in terms of Rydberg series that arise from promotion of an electron from the highest occupied 2bl molecular orbital. The electronic symmetries of states involved in six Rydberg series have been established unambiguously through observation of the (partially resolved) rotational structure that accompanies their excitations. A number of additional resonances observed only in the multiphoton ionisation spectra are tentatively attributed to excitations involving Rydberg orbitals comprised predominantly o f f and/or g functions. Several of the absorption features (most notably those involving excited sites of B, symmetry) exhibit anomalous intensity distributions between the various rotational branches. L-uncoupling and/or rovibronic level dependent predissociation are suggested as contributory causes.

Vertical Excitation Energies and Ionization Potentials of H2S. A Size-Consistent Self-Consistent Singles and Doubles Configuration Interaction (SC)2-MR-SDCI Calculation

“…Different experimental VEE values have been reported for the 1 B 1 (5s) state, such as that of 8.13 eV by Ashfold et al 8,10 and that of 8.84 eV by Masuko et al 4 The present work predicts a VEE of 8.7 eV for this state, and the wave function reflects an important mixing between 3d and 5s Rydberg excitations. The comparison with the results by D&L 7 is excellent, as they locate the 1 B 1 (3d z 2 ), 1 B 1 (5s), and 1 B 1 (3d x 2 -y 2 ) states at VEE's of 8.48, 8.80, and 8.98 eV, respectively.…”

“…While Ashfold et al 10 and Mayhew et al 8 report values of 9.27 and 9.77 eV, respectively, the ones measured by Masuko et al 4 were 9.66 for 1 B 1 (6s) and 9.94 eV for 1 B 1 (7s). The present (SC) 2 theoretical values are 9.55 eV for the 1 B 1 (6s) state and 9.81 eV for the 1 B 1 (7s) state, in better agreement with those of ref 4 than the ones of ref 10, but still slightly too low in magnitude.…”

“…The VEE's of the four 1 B 1 , 1 B 2 , and 1 A 1 4d states are located experimentally between 9.44 and 9.60 eV. The three series C, D, and E occur at excitations of 9.44, 9.54, and 9.60 eV, 8 respectively. The (SC) 2 -MR-SDCI values for these states fall within a narrow range of 0.1 eV, which is of the same order as that of the experimental values.…”

“…The f Rydberg states have not been studied before, despite being located within the same energy ranges as those of many s, p, and d states. Some data concerning their location can be found in the work of Mayhew et al 8 (even though the 3+1 MPI spectra measured by these authors are inconclusive on this aspect) and in the work by Ashfold et al 10 A problem that concerns the present calculations is the large number of existing states. For example, states belonging to the B 1 symmetry surpass the number of 20 states in only the 6-10 eV energy range.…”

Two-photon resonance enhanced multiphoton ionization photoelectron spectroscopy of the SH (SD) radical below and above the lowest ionization threshold

“…Attempts to detect REMPI transitions for the SH radical in this region were not successful. 51 We can consequently conclude that the observed Rydberg state is built upon the excited a 1 ⌬ ͑v ϩ ϭ0͒ ionic state. The dependence of the two-photon excitation spectra on the polarization of the excitation light would seem to indicate that the sparse rotational structure in Figs.…”