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All-channel time-dependent quantum mechanical reaction probabilities are reported for the collinear He + H + 2 (ν = 0, 1, 2) → HeH + + H reaction at a total energy of 1.2 eV on previously reported diatomics-in-molecule (DIM) and spline fitted ab initio (SAI) surfaces. These results are in agreement with the previous quasiclassical trajectory results in that there is vibrational enhancement of the reaction probability on the SAI surface but not on the DIM surface. This agreement lends support to our previously drawn conclusion that small differences in the potential-energy surface can lead to substantially different dynamic results.

An ab initio computation of the energy transfer dynamics in the (CO2,H2) and (CO2,D2) systems has been carried out. The intermolecular potential energy hypersurface has been obtained from the results of ab initio SCF computations using extended Gaussian basis sets. The potential energy has been computed for 1053 different geometries. Previously formulated cubic spline fitting procedures are employed to effect surface interpolation and to extract surface gradients. At small CO2–H2 center‐of‐mass separations, the potential energy is repulsive and nearly exponential in form. At larger separations, small attractive wells are found. At a given separation, the most stable conformation is a planar, parallel structure of C2v symmetry. Vibrational deexcitation probabilities, energy transfer mechanisms, and isotope ratios for the relaxation of the first excited state of the doubly degenerate bending mode of CO2 have been computed as a function of temperature by quasiclassical trajectories. In the temperature range ...

The reaction probabilities for He+H+2(v=0,1,2,3) →HeH++H have been computed as a function of total energy using quasiclassical trajectory procedures. The potential‐energy surface was obtained by employing 2D cubic spline interpolation of previously reported ab initio SCF results. The calculated reaction probabilities are found to be significantly increased whenever the total energy is selectively partitioned into H+2 vibration. These results are in accord with previously reported experimental findings but are in contrast to previous quantum mechanical calculations on a DIM analytic fit to the ab initio surface points. It is shown that this discrepancy is a result of small differences between the splinefitted and DIM surfaces and not to either the collinear nature of the computations or the differences between quantum and quasiclassical procedures.

Results of quasiclassical trajectory studies of CO2 (Ji=0, 16, 30)–H2 (Ji=0, 2) collisions at Etot=0.1, 0.2 eV are reported in terms of state‐to‐state integral inelastic cross sections, first moments of energy transferred in excitation and de‐excitation processes and C values which characterize the variation of the rotational suprisal with energy gap between initial and final states. The magnitude of the first moments are shown to increase with increasing translational energy Ti and with the initial rotational state JiCO2. The value of C decreases with increasing Ti. It is found to be strongly dependent upon JiCO2 but depends only weakly upon JiH2. Comparison of our results with those of Preston and Pack for the CO2–He and CO2–Ar systems reveals that although the qualitative dependence of σ−, σ+, σ, 〈ΔE−〉 and 〈ΔE+〉 upon Ti and JiCO2 is the same in all three systems, there are quantitative differences which reflect the atomic (molecular) size of He, H2, and Ar. Furthermore, the suprisal parameter is distin...

Results of a three-dimensional quasiclassical trajectory investigation of the orientation dependence of the reaction cross section and the product energy distribution are reported for the title reaction on an ab initio potential-energy surface. The reaction is preferred at the F end rather than at the H end of the molecule. Also, the attack by the Li atom at the F end of the molecule leads to a large product rotational excitation while a broadside attack favors a higher vibrational excitation. This is attributed to the collissions occuring at larger impact parameters for the former than for the latter.