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The explicit consideration of the vector correlations is an essential step when it comes to determining the mechanism of chemical reactions. Usual vector correlations involve initial and final relative velocity vectors and rotational angular momenta. However, the correlation between the orbital, l, and rotational, j, angular momenta has seldom received any attention. In this article, we present a semiclassical methodology capable of describing the l-j correlation that may serve as a connection between the quantum and quasiclassical treatments. Using the scattering matrix in the orbital angular momentum representation, the l-j correlation is expressed as a probability density function of the angle formed by both vectors. This technique is exemplified through the H + D2 reaction and its accuracy is appraised by comparing with results derived from calculations based on quasiclassical trajectories. [ABSTRACT FROM AUTHOR]

We have characterized the stereodynamics of the H + LiH (v = 0, j = 0-1) reactive collisions leading to H2 formation through the quantum mechanical analysis of the k-j and k'-j' vector correlations that describe the polarization of the reactants and products, respectively. Our results, which cover the collision energy interval between 10-4 and 1 eV, are unexpectedly complex given the apparent simplicity and featureless nature of the potential energy surface for the LiH2 system and point toward the existence of a dynamical barrier connected to the centrifugal barrier. Both reactants and products, in particular the second ones, display strong directional preferences in the cold region that indicate a bias for collinear approaching and departing geometries and are independent of the final state of the products. As more energy is available for the reaction, the polarization of reactants and products becomes weaker and strongly dependent on the final state. While stereodynamical control is feasible and significant in the cold region, its extent becomes negligible for other energetic regimes. [ABSTRACT FROM AUTHOR]

Time-independent quantum mechanicalcalculations have been performedin order to characterize the dynamics and stereodynamics of Cl + HDreactive collisions. Calculations have been carried out at two differenttotal energy values and for various initial states using the adiabaticpotential energy surface by Bian and Werner [J. Chem. Phys.2000, 112, 220]. Special attentionhas been paid to the reaction with HD(v= 1) forwhich integral and differential cross-sections have been calculatedand the effect of vibrational vs translational energy on the reactivityhas been examined. In addition, the reactant polarization parametersand polarization-dependent differential cross-sections have been determined.From these results, the spatial preferences of the reaction and theextent of the control of the cross sections achievable through a suitablepreparation of the reactants have been also studied. The directionalrequirements are tighter for the HCl channel than for the DCl one.Formation of the products takes place preferentially when the rotationalangular momentum of the HD molecule is perpendicular to the reactantsapproach direction. Cross-sections and polarization moments computedfrom the scattering calculations have been compared with experimentalresults by Kandel et al. [J. Chem. Phys.2000, 112, 670] for the reaction with HD(v= 1) produced by stimulated Raman pumping. The agreement so obtainedis good, and it improves the accordance found in previous calculationswith other methodologies and potential energy surfaces. [ABSTRACT FROM AUTHOR]

The dynamics and kinetics of the LiH + H reaction have been studied by using an accurate quantum reactive time-dependent wave packet method on the ab initio ground electronic state potential energy surfaces (PES) developed earlier. Reaction probabilities for the two possible reaction channels, the LiH + H→ H2 + Li depletion process and the LiH + H→H + LiH hydrogen exchange reaction, have been calculated from 1 meV up to 1.0 eV collision energies for total angular momenta J from 0 to 80. State-to-state and total integral cross sections for the LiH-depletion and H-exchange channels of the reaction have been calculated over this collision energy range. It is found that the LiH-depletion channel is dominant in the whole range of collision energies for both PESs. Accurate total rate coefficients have been calculated on both surfaces from 100 K to 2000 K and are significantly larger than previous empirical estimates and previous J-shifting results. In addition, the present accurate calculations present noticeable differences with previous calculations using the centrifugal sudden approximation. [ABSTRACT FROM AUTHOR]