Velocity selection and mass spectrometric detection of an H2S molecular beam and a collisional study of its interactions with rare gases

Total integral cross section experiments, for collisions of rotationally hot H2S projectile molecules by He and Xe targets, have been performed in the thermal energy range by using a molecular beam apparatus, which operates under high resolution conditions and exploits a quadrupole mass spectrometer as a detector. Information on the radial dependence of the intermolecular interaction, averaged over all relative orientations of colliding partners, is obtained. This study completes the investigation of H2S-rare gas family [see D. Cappelletti, A.FA. Vilela, P.R.P. Barreto, R. Gargano, F. Pirani, V. Aquilanti, J. Chem. Phys. 125 (2006) 133111, for Ne, At and Kr] and permits us to discover similarities and differences with the analogous H2O-Rg series of systems. In particular, the analysis of the scattering data suggests that while the complexes of H2S-rare gases from He to Kr are essentially bound by nearly isotropic noncovalent interactions of van der Waals type, the H2S-Xe system exhibits a weak, but measurable, additional component which emerges at intermediate intermolecular distance (in proximity of the potential well), and provides a bond stabilization. This observation is of possible interest for the investigation of the phenomenology of the hydrogen bond formation. (C) 2008 Elsevier B.V. All rights reserved.