The effect of the intermolecular potential formulation on the state‐selected energy exchange rate coefficients in N₂–N₂ collisions

Abstract

The rate coefficients for N2-N2 collision-induced vibrational energy exchange (important for the enhancement of several modern innovative technologies) have been computed over a wide range of temperature. Potential energy surfaces based on different formulations of the intramolecular and intermolecular components of the interaction have been used to compute quasiclassically and semiclassically some vibrational to vibrational energy transfer rate coefficients. Related outcomes have been rationalized in terms of state-to-state probabilities and cross sections for quasi-resonant transitions and deexcitations from the first excited vibrational level (for which experimental information are available). On this ground, it has been possible to spot critical differences on the vibrational energy exchange mechanisms supported by the different surfaces (mainly by their intermolecular components) in the low collision energy regime, though still effective for temperatures as high as 10,000 K. It was found, in particular, that the most recently proposed intermolecular potential becomes the most effective in promoting vibrational energy exchange near threshold temperatures and has a behavior opposite to the previously proposed one when varying the coupling of vibration with the other degrees of freedom.

Efficiency of Collisional O2 + N2 Vibrational Energy Exchange

“…The Figure clearly shows that the GB1 V-V transfer is systematically larger than the MF ones (though it lowers as T decreases as already found for N 2 + N 2 in Ref. 10) As to item (b) a rst point to make is that the v a = 19 process, O 2 (v a = 19) as found also for the larger v transitions already considered, the SC RC for the O 2 (v a = 0)…”

Atomic and molecular data for spacecraft re-entry plasmas

“…Even if in principle the intermolecular potentials can be characterized in detail by molecular beam scattering experiments [182] and spectroscopic studies of van der Waals complexes [183], the inference from the measured data is a difficult inversion problem. An accurate PES can be obtained by an efficient GEMS procedure that adopts a parametric model potential and then varies tentatively the value of the parameters so as to obtain from the integration of the dynamical equations the best possible agreement with experimental results to reproduce the glory oscillations and the second virial coefficient for diatom-diatom systems [55]. Moreover, since vibrations and rotations distort the molecular geometry, affecting both polarizabilities and charge distributions, the intermolecular forces, related to such properties, are strongly dependent on the quantum states of the interacting monomers and so are the outcomes of collision events.…”

Energy transfer dynamics and kinetics of elementary processes (promoted) by gas‐phase CO2‐N2 collisions: Selectivity control by the anisotropy of the interaction

“…[64]) to represent its V intra term, while for N 2 a Morse potential has been adopted (similarly to what has been done in Refs. [7,65]). In the trajectories, the initial vibrational states of the molecules are explicitly selected, while the initial rotational states and the relative velocity of the colliding partners are assigned by sampling the related Boltzmann distributions.…”

“…Since it is clearly inconceivable to set up collision experiments covering the entire range of conditions and of molecular quantum states met in the variety of the applications, for rate coefficients and related quantities the only viable approach is their calculation by means of molecular collisions simulations. [6] To this end a point that has been since long understood is that energy transfer is very sensitive to the strength and shape of the intermolecular potentials, [7,8] and the accuracy of transition probabilities, cross sections and rate coefficients is therefore highly dependent on the detailed knowledge of such interactions. In principle, intermolecular potentials can be characterized by both molecular beam scattering experiments (see, e.g., [8] ) and spectroscopic studies of van der Waals complexes.…”