Stereodynamical Effects by Anisotropic Intermolecular Forces

Abstract

Electric and magnetic field gradients, arising from sufficiently strong anisotropic intermolecular forces, tend to induce molecular polarization which can often modify substantially the results of molecular collisions, especially at low rotational temperatures and low collision energies. The knowledge of these phenomena, today still not fully understood, is of general relevance for the control of the stereo-dynamics of elementary chemical-physical processes, involving neutral and ionic species under a variety of conditions. This paper reports on results obtained by combining information from scattering, spectroscopic and reactivity experiments, within a collaboration between the research groups in Perugia and Trento. We addressed particular attention to the reactions of small atomic ions with polar neutrals for their relevance in several environments, including interstellar medium, planetary atmospheres, and laboratory plasmas. In the case of ion-molecule reactions, alignment/orientation is a general phenomenon due to the electric field generated by the charged particle. Such phenomenon originates critical stereo-dynamic effects that can either suppress (when the orientation drives the collision complex into non-reactive or less reactive configurations), or enhance the reactivity (when orientation confines reagents in the most appropriate configuration for reaction). The associated rate coefficients show the propensity to follow an Arrhenius and a non-Arrhenius behavior, respectively.

Old School Techniques with Modern Capabilities: Kinetics Determination of Dynamical Information Such as Barriers, Multiple Entrance Channel Complexes, Product States, Spin Crossings, and Size Effects in Metallic Ion–Molecule Reactions

“…Quantitative understanding of the stereodynamics in reactions such as these is a daunting computational task requiring detailed calculations of the long and intermediate range potentials. 147 Statistical modeling and temperature- dependent kinetics prove to be a tractable tool in elucidating the essential parameters along the potential surface while highlighting systems of particular interest for more detailed theoretical treatment. Metal Cluster Anion Oxidation.…”

“…The increased rotation of ClF with increasing temperature could diminish this effect, allowing increased formation of the reactive F side complex resulting in the increased efficiency observed. Quantitative understanding of the stereodynamics in reactions such as these is a daunting computational task requiring detailed calculations of the long and intermediate range potentials . Statistical modeling and temperature-dependent kinetics prove to be a tractable tool in elucidating the essential parameters along the potential surface while highlighting systems of particular interest for more detailed theoretical treatment.…”

Catalytic Oxidation of CO by N2O Enabled by Al2O2/3+: Temperature Dependent Kinetics and Statistical Modeling

“…Quantified understanding of stereodynamics such as this in ion–molecule reactions is still in development . Commonly, examples of asymmetric entrance channel formation, or “orienting”, in ion–molecule reactions involve neutral reactants with large (>1D) dipole moments .…”

The role of precursor states in the stereo-dynamics of elementary processes

“…Within a collaboration between Perugia and Trento groups, it has been also demonstrated, by exploiting simultaneously spectroscopic and scattering probes, that benzene in seeded beams shows the molecular propensity to fly like frisbees. 35,36…”