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The stereodynamics of the Ar + NO (J = 0) rotational inelastic excitation has been investigated at 66 meV by means of quasiclassical trajectories on a recent ab initio potential energy surface. A marked correlation between the preferred sense of rotation of NO and the scattering plane is obtained for the highest rotational levels accessible, which are excited in strong repulsive collisions. This result is in qualitative agreement with recent quantum mechanical calculations and experimental measurements. For the lower rotational levels, where the interactions are not so repulsive, the preferred sense of rotation is found to oscillate with scattering angle, but the intensity of the oscillations is small and their angular range is not entirely coincident with those from quantum mechanics and experiment. Classical dynamics, even including attractive interactions, cannot account properly for the mentioned oscillatory behaviour. Secondary encounters between the outgoing Ar atom and NO molecule, giving rise to 'chattering', are found to be relatively frequent, leading to a decrease in the final rotational energy of NO with respect to that attained in the first encounter. Chattering trajectories are defined and their mechanism is characterized. © Royal Society of Chemistry ; Funded by the Ministry of Science and Technology of Spain under grants BQU2002-04627-C02 and REN 2000-1557 and by the European Union through the RTN Reaction Dynamics(HPRN-CT-1999-0007). The research was performed within the Unidad Asociada ''Química Física Molecular'' between the Universidad Complutense and the CSIC. ; Peer Reviewed

8 págs.; 5 figs.; 1 tab. ; Open Access funded by Creative Commons Atribution Licence 4.0 ; In the last decade, the development of theoretical methods has allowed chemists to reproduce and explain almost all of the experimental data associated with elementary atom plus diatom collisions. However, there are still a few examples where theory cannot account yet for experimental results. This is the case for the preferential population of one of the Λ-doublet states produced by chemical reactions. In particular, recent measurements of the OD( Π) product of the O(P)+D reaction have shown a clear preference for the Π (A′) Λ-doublet states, in apparent contradiction with ab initio calculations, which predict a larger reactivity on the A″ potential energy surface. Here we present a method to calculate the Λ-doublet ratio when concurrent potential energy surfaces participate in the reaction. It accounts for the experimental Λ-doublet populations via explicit consideration of the stereodynamics of the process. Furthermore, our results demonstrate that the propensity of the π (A′) state is a consequence of the different mechanisms of the reaction on the two concurrent potential energy surfaces. ; We acknowledge funding by the Spanish Ministry of Economy and Competitiveness (grants CTQ2012-37404-C02, CTQ2015-65033-P and Consolider Ingenio 2010 CSD2009-00038). M.B. gratefully acknowledges the support of the U.K. EPSRC (via Programme Grant EP/L005913/1). P.G.J. acknowledges the Spanish Ministry of Economy and Competitiveness for the Juan de la Cierva fellowship (IJCI-2014-20615). A.Z. acknowledges the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement number 610256 (NANOCOSMOS). ; Peer Reviewed

9 p.: gráf. ; Integral cross sections and thermal rate constants have been calculated for the N 2D +H2 reaction and its isotopic variants N 2D +D2 and the two-channel N 2D +HD by means of quasiclassical trajectory and statistical quantum-mechanical model methods on the latest ab initio potential-energy surface T.-S. Ho et al., J. Chem. Phys. 119, 3063 2003 . The effect of rotational excitation of the diatom on the dynamics of these reactions has been investigated and interesting discrepancies between the classical and statistical model calculations have been found. Whereas a net effect of reagent rotation on reactivity is always observed in the classical calculations, only a very slight effect is observed in the case of the asymmetric N 2D +HD reaction for the statistical quantum-mechanical method. The thermal rate constants calculated on this Potential-Energy Surface using quasiclassical trajectory and statistical model methods are in good agreement with the experimental determinations, although the latter are somewhat larger. A reevaluation of the collinear barrier of the potential surface used in the present study seems timely. Further theoretical and experimental studies are needed for a full understanding of the dynamics of the title reaction. © 2005 American Institute of Physics. ; Financial support through the Ramón y Cajal program from the Spanish Ministry of Education and Science. This work has been funded by the Ministry of Education and Science of Spain under Grant Nos. BQU2002-04627-C02-02, FTN2003-08228-CO3-03, and FIS2004-02461 and CAM 07N/0058/2002 and by the European Union through the RTN Reaction Dynamics HPRN-CT-1999-0007 and Project No. MERGCT-2004-513600. The research was performed within the Unidad Asociada "Química Física Molecular" between the Universidad Complutense and the CSIC. ; Peer reviewed

The rotationally inelastic scattering of NO by Ar was studied on a potential energy surface at the collision energy of a high resolution experiment. The study entailed the calculationm of the state-resolved integral and differential cross sections for all the excited levels of NO in the lowest spin-orbit manifold. The quasiclassical approach was shown to satisfactorily reproduce few observations seen in both the experimental and quantum mechanical state-resolved differential cross-sections. © 2003 American Institute of Physics ; Funded by the Ministry of Science and Technology of Spain under Grants No. BQU2002-04627-C02 and No. REN 2000-1557, by the European Union through the RTN Reaction Dynamics ~HPRN-CT-1999-0007!, and by the U.S. National Science Foundation ~Grant No. CHE-9971810! The research was performed within the Unidad Asociada ''Química Física Molecular'' between the Universidad Complutense and the CSIC. ; Peer Reviewed