Classical collision complexes in the D+H2(v=0, j=0)→HD(v′, j′)+H reaction

Detailed quasiclassical trajectory calculations of the D+H2(v=0, j=0)→HD(v′=0, j′)+H have been carried out in the range of collision energy from 0.35 to 1.25 eV. The calculated v′j′ state resolved differential cross sections and opacity functions show analogous structures to the ones obtained by accurate quantum mechanical results, that is, a peak along a line in the E−θ (or E−J) plane, that was attributed to broad resonances. Analysis of present results in terms of the duration of the collision indicates that those trajectories pertaining to these peaks proceed through the formation of short lived collision complexes with lifetimes of 15–35 fs. © American Institute of PhysicsPartly financed by the CICYT of Spain under Grant No. PB890041.Peer Reviewe

Stereodynamical Control of a Quantum Scattering Resonance in Cold Molecular Collisions

Cold collisions of light molecules are often dominated by a single partial wave resonance. For the rotational quenching of HD (v=1, j=2) by collisions with ground state para-H2, the process is dominated by a single L=2 partial wave resonance centered around 0.1 K. Here, we show that this resonance can be switched on or off simply by appropriate alignment of the HD rotational angular momentum relative to the initial velocity vector, thereby enabling complete control of the collision outcome

Non-adiabatic quantum dynamics of the electronic quenching OH(A(2)sigma(+)) + Kr

We present the dynamics of the electronic quenching OH(A2S+) + Kr(1S)-OH(X2P) + Kr(1S), withOH(A2S+) in the ground ro-vibrational state. This study relies on a new non-adiabatic quantum theorythat uses three diabatic electronic statesS+,P0, andP00, coupled by one conical-intersection and nineRenner-Teller matrix elements, all of which are explicitly considered in the equation of the motion. Thetime-dependent mechanism and initial-state-resolved quenching probabilities, integral cross sections,thermal rate constants, and thermally-averaged cross sections are calculatedviathe real wavepacketmethod. The results point out a competition among three non-adiabatic pathways:S+2P0,S+2P00,andP02P00. In particular, the conical-intersection effectsS+-P0are more important than theRenner-Teller couplingsS+-P0,S+-P00, andP0-P00. Therefore,P0is the preferred product channel.The quenching occursviaan indirect insertion mechanism, opening many collision complexes, and theprobabilities thus present many oscillations. Some resonances are still observable in the cross sections,which are in good agreement with previous experimental and quasi-classical findings. We also discussthe validity of more approximate quantum methods

The D+H2(v=1,j)→HD(v′,j′)+H reaction. A detailed quasiclassical trajectory study

Thorough quasiclassical trajectory (QCT) calculations have been carried out for the D+H2(v =1,j) exchange reaction. These calculations include integral and differential cross sections, rate constants, reaction probabilities as a function of total energy, opacity functions, and distributions of internal states of the HD product in the range of collision energies from the reaction threshold to 1.5 eV and initial j values from 0 to 12. An overall good agreement with some discrepancies is found between the present QCT results and those from experiments and accurate quantum-mechanical calculations. © 1994 American Institute of Physics.German-Spanish scientific exchange program >Acciones Integradas HispanoAlemanas,> under Project No. HA-063. Financial support by the DGICYT under Project No. PB92-0219-C03.Peer Reviewe

Influence of the reactants rotational excitation on the H + D2(v = 0, j) reactivity

10 págs.; 10 figs.; 1 tab.; Special Issue: Dynamics of Molecular Collisions XXV: Fifty Years of Chemical Reaction DynamicsWe have analyzed the influence of the rotational excitation on the H + D(v = 0, j) reaction through quantum mechanical (QM) and quasiclassical trajectories (QCT) calculations at a wide range of total energies. The agreement between both types of calculations is excellent. We have found that the rotational excitation largely increases the reactivity at large values of the total energy. Such an increase cannot be attributed to a stereodynamical effect but to the existence of recrossing trajectories that become reactive as the target molecule gets rotationally excited. At low total energies, however, recrossing is not significant and the reactivity evolution is dominated by changes in the collision energy; the reactivity decreases with the collision energy as it shrinks the acceptance cone. When state-to-state results are considered, rotational excitation leads to cold products rovibrational distributions, so that most of the energy is released as recoil energy.The authors acknowledge funding by the Spanish Ministry of Science and Innovation (grant Consolider Ingenio 2010 CSD2009-00038). J.A., F.J.A. and P.G.J. acknowledge also funding by the Spanish Ministry of Economy and Competitiveness (grant CTQ2012-37404-C02), and V.J.H. acknowledges additional funding by the Spanish Ministry of Science and Innovation (FIS2013-48087-C2-1P) and by the European Research Council (ERC-2013-Syg-610256).Peer Reviewe

Attractive and repulsive interactions in the inelastic scattering of NO by Ar: A comparison between classical trajectory and close-coupling quantum mechanical results

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 PhysicsFunded 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 Reviewe

Cumulative reaction probabilities and transition state properties: A study of the H++H2 and H++D2 proton exchange reactions

10 pages, 6 figures.Cumulative reaction probabilities (CRPs) have been calculated by accurate (converged, close coupling) quantum mechanical (QM), quasiclassical trajectory (QCT), and statistical QCT (SQCT) methods for the H++H2 and H++D2 reactions at collision energies up to 1.2 eV and total angular momentum J=0–4. A marked resonance structure is found in the QM CRP, most especially for the H system and J=0. When the CRPs are resolved in their ortho and para contributions, a clear steplike structure is found associated with the opening of internal states of reactants and products. The comparison of the QCT results with those of the other methods evinces the occurrence of two transition states, one at the entrance and one at the exit. At low J values, except for the quantal resonance structure and the lack of quantization in the product channel, the agreement between QM and QCT is very good. The SQCT model, that reflects the steplike structure associated with the opening of initial and final states accurately, clearly tends to overestimate the value of the CRP as the collision energy increases. This effect seems more marked for the H++D2 isotopic variant. For sufficiently high J values, the growth of the centrifugal barrier leads to an increase in the threshold of the CRP. At these high J values the discrepancy between SQCT and QCT becomes larger and is magnified with growing collision energy. The total CRPs calculated with the QCT and SQCT methods allowed the determination of the rate constant for the H++D2 reaction. It was found that the rate, in agreement with experiment, decreases with temperature as expected for an endothermic reaction. In the range of temperatures between 200 and 500 K the differences between SQCT and QCT rate results are relatively minor. Although exact QM calculations are formidable for an exact determination of the k(T), it can be reliably expected that their value will lie between those given by the dynamical and statistical trajectory methods.This work has been funded by the MICIN (Spain) under Project Nos. CTQ2008-02578, CTQ2005-09185, FIS2007- 62006 ENE2006-14577-C04-Co3/FTN, and FIS2007-61686. P.G.J. also acknowledge support from the fellowship Grant No. Grant AP2006-03740.Peer reviewe