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.F.A. Vilela, P.R.P. Barreto, R. Gargano, F. Pirani, V. Aquilanti, J. Chem. Phys. 125 (2006) 133111, for Ne, Ar 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.