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

Universal behavior in complex-mediated reactions: Dynamics of S(1D)+ o-D2 --> D + SD at low collision energies

Reactive and elastic cross-sections, and rate coefficients, have been calculated for the S(1D)+ D2 (v=0, j=0) reaction using a modified hyperspherical quantum reactive scattering method. The considered collision energy ranges from the ultracold regime, where only one partial wave is open, up to the Langevin regime, where many of them contribute. This work presents the extension of the quantum calculations, which were compared with the experimental results in a previous work, down to energies in the cold and ultracold domains. Results are analyzed and compared with the universal case of the quantum defect theory by Jachymski et al. [Phys. Rev. Lett. 110, 213202 (2013)]. State-to-state integral and differential cross sections are also shown covering the ranges of low-thermal, cold and ultracold collision energy regimes. It is found that at E/k_B T < 1 K there are substantial departures from the expected statistical behavior, and that dynamical features become increasingly important with decreasing collision energy, leading to vibrational excitation.Comment: Submitted to Journal of Chemical Physic

Quasiclassical trajectory study of the dynamics of the H+N₂O reaction on a new potential energy surface

A new ab initiopotential energy surface (PES) for the H+N₂O→OH+N₂reaction has been constructed using the GROW package of Collins and co-workers. The ab initio calculations have been done using the Becke three-parameter nonlocal exchange functional with the nonlocal correlation of Lee, Yang, and Parr density functional theory. A detailed quasiclassical trajectory study of integral and differential cross sections, product rovibrational populations, and internal energy distributions on the new PES is presented. The theoretical integral cross sections as a function of collision energy are in qualitative agreement with the experimental measurements. A good correspondence is found between the calculated OH(v′=0,1) rovibrational populations and the recent measurements of Brouard and co-workers at 1.48 eV collision energy. In particular, the calculated kinetic energy release distributions for state resolved OH(v′,N′) products predict a substantial fraction of total energy going into rotational excitation of the N₂ co-product, in good agreement with the experimental findings.The Spanish part of this work has been financed by DGES of Spain (Project No. PB98-0762-C02-01) and by the European Commission within the RT Network Reaction Dynamics (Contract No. HPRN-CT-1999-00007)

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

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