1,721,007 research outputs found
Polar molecules engaged in pendular states captured by molecular-beam scattering experiments
No full textWe demonstrate that when two polar molecules as those of water, ammonia, and hydrogen sulfide encounter each other at a distance much larger than their dimensions they engage a synchronous motion that promotes the transformation of free rotations into coupled pendular states. This discovery has been prompted by high-resolution molecular beam scattering experiments presented here, addressed to the measure of the total integral cross section changes as a consequence of molecular rotation couplings. The experimental observations and the theoretical treatment developed to shed light on the details of the phenomenon suggest that the interplay among free rotations and pendular states depends on the relative velocity, on the rotational levels, and on the dipole moments of the interacting molecules. The features of this intriguing phenomenon may be crucial for the interpretation and the control of basic chemical and biological processes
Intermolecular potential energy surfaces for the interaction between H2X (X = O, S) and metastable Ne*(3P2,0) atom
No full textPotential energy surfaces for the interaction of a Ne*(3P2,0) atom with H2O and H2S molecules are obtained on the basis of a semi empirical method that has been previously used for some specific orientations in Ne*(3P2,0)–H2O system. The method is now suitable for all orientations and also for Ne*(3P2,0)–H2S system. Interesting features emerge by comparing the two systems and appear related to different characteristics of the two molecular partners. The potential energy surface for Ne*(3P2,0)–H2S has been also successfully tested for reproducing recent experimental Penning ionization electron spectroscopy data, sensible to some specific orientations of the two colliding partners
The role of charge transfer in the stability and reactivity of chemical systems from experimental findings
No full textPhenomena are described within a unifying picture, by isolating charge/electron transfer as an interaction component triggering chemical reactivity.</p
Metastable hydrogen atom scattering by crossed beams: total integral cross sections for H*(2s)-Ar, Kr, Xe, O2, Cl2, and CCl4 at thermal energies
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Penning Ionization Electron Spectroscopy of Hydrogen Sulfide by Metastable Helium and Neon Atoms
No full textThe dynamics of the Penning ionization of hydrogen sulfide
molecules by collision with helium and metastable neon atoms, occurring in the thermal energy range, has been studied by analyzing the energy spectra of the emitted electrons obtained in our laboratory in a crossed beam experiment. These spectra are compared with the photoelectron spectra measured by using He(I) and
Ne(I) photons under the same experimental conditions. In this way we obtained the negative energy shifts for the formation of H2S+ ions in thefirst three accessible electronic states by He*(23,1S1,0) and Ne*(3P2,0) Penning ionization collisions: the 2b1 (X2B1) fundamental one, thefirst 5a1 (A2A1), and the second 2b2 (B2B2) excited states, respectively. The recorded energy shifts indicate that in the case of He* and Ne*−H2S the autoionization dynamics depends on the features of the collision complex and is mainly driven by an effective global attraction that comes from a balance among several non covalent intermolecular interaction components. This suggests that the Penning ionization should take place, in a specific range of intermolecular distances, as we have already observed in the case of Penning ionization of water molecules [Brunetti, B. G.;
Candori, P.; Falcinelli, S.; Pirani, F.; Vecchiocattivi, F. J. Chem. Phys. 2013, 139, 164305-1−164305-8]
A molecular beam scattering investigation of methanol–noble gas complexes: Characterization of the isotropic potential and insights into the nature of the interaction
No full textIntegral cross section experiments involving rotationally hot CH3OH projectiles and noble gas (Ng = Ne,
Ar, Kr and Xe) targets are reported for the first time. Measured data have been exploited to characterize
the phenomenological radial interaction in the CH3OH–Ng weakly bound complexes. Potential energy
surfaces for all the systems have been formulated on the basis of a pairwise additive multicenter model.
The comparison of model predictions with the most relevant experimental findings suggests that in
CH3OH–Ng complexes, at variance with the behavior of the analogous complexes involving water or
ammonia, the interaction is mainly due to van der Waals and induction components
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