Rate constants for the electronic quenching reaction N( 2 D) + N 2 → N( 4 S) + N 2 are calculated for temperatures over the range of 240 ≤ T/K ≤ 1000 using an accurate set of three global electronic potential energy surfaces for the N 3 system ( 4 A″, 2 A′, and 2 A″). The nuclear motion is treated by running quasiclassical trajectories, incorporating spin-forbidden transitions with the trajectory surface hopping method. The exclusively theoretical results are compared with available experimental data for the reaction and contribute to clarify the discrepancies among them. The rate constants at higher temperatures achieved in the atmosphere, for which no experiments have been performed, are presented for the first time. The impact of the results in atmospheric modeling is analyzed, predicting at what altitudes this reaction will play an important role.

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We report a new global double many-body expansion potential energy surface for the ground state of the CNO(A') manifold, calculated by the explicit correlation multireference configuration interaction method. The functional form was accurately fitted to 3701 ab initio points with a root mean squared deviation of 0.99 kcal mol. All stationary points reported in previous forms are systematically described and improved, in addition to three new ones and a characterization of an isomerization transition state between the CNO and NCO minima. The novel proposed form gives a realistic description of both short-range and long-range interactions and hence is commended for dynamics studies.

Energetics and possible stable structures of CO2–Arn (n = 1–21) clusters are investigated by performing molecular-dynamics simulations. The pairwise-additive approximation is tested to construct the potential energy function for describing the non-rigid particle interactions in the system. A potential model by Pariseau et al. (Journal of Chemical Physics, Vol. 42, p. 2335, 1965) is used for the internal motion of the CO2 molecule and the Billing form potential (Chemical Physics, Vol. 185, p. 199, 1994) is used for all other pair interactions. The stable configurations are determined for the ground state of CO2–Arn clusters, and the growing pattern process of the clusters is determined via rearrangement collisions. Ar atoms tend to surround the CO2 molecule, and the clusters prefer to form three-dimensional compact structures. Obtained structures and energetics are in quantitative agreement with previous results (Journal of Chemical Physics, Vol. 109, p. 1343, 1998) that have used split-repulsion and ab initio potentials in which the molecule was treated as rigid.Key words: argon, CO2, cluster, potential energy function, molecular dynamics.

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