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We investigate the usefulness of density functional theory (DFT) for calculating excited state potential energy surfaces. In the DFT calculations, the generalized gradient approximation (GGA) is used. As a test case, the photodissociation of H2O through the first excited A 1B1 state was considered. Two‐dimensional potential energy surfaces were obtained for both the X 1A1 ground state and the first excited state. Wave packet calculations employing these surfaces were used to obtain both the absorption spectrum and partial photodissociation cross sections, which are resolved with respect to the final vibrational state of the OH fragment. Comparisons are made with a previously calculated high level ab initio potential energy surface, with dynamics calculations using that surface, and with experiment. The vertical excitation energy for the (X 1A1→A 1B1) transition calculated using DFT is in good agreement with the previous ab initio calculations. The absorption spectrum and the partial cross sections obt...

The H2+LiF(001) system was used to investigate the performance of the hybrid close‐coupling wave packet (CCWP) method and of a symmetry adapted, fully close‐coupled wave packet (SAWP) method for a molecule–surface problem characterized by fairly high corrugation. In the calculations, a realistic, φ‐dependent model potential was used. The calculations were performed for a collision energy of 0.2 eV, with H2 initially in its j=0 rotational state at normal incidence to the surface. Large increases in the computational efficiencies of both wave packet methods were achieved by taking advantage of the potential coupling matrices associated with both methods becoming sparser with increasing molecule–surface distance. For the present model problem and employing this increased sparseness at longer range, the SAWP method is faster than the CCWP method by a factor of 2. The potential usefulness of the SAWP method for dissociative chemisorption problems is discussed.

The close‐coupling wave packet (CCWP) method has been adapted for performing calculations on molecule‐surface scattering with arbitrary angles of incidence. The method used involves a slight modification of the fast Fourier transform (FFT) technique for evaluating the action of the translational kinetic energy operator on the wave function, employing the shifting theorem of Fourier analysis. We present and compare results of CCWP and close‐coupling (CC) calculations on the He+LiF and H2+LiF systems using simple model potentials. The results presented establish the validity of the proposed technique and may be useful as benchmarks.

Results of quantum calculations on rotationally and vibrationally inelastic scattering of rotationally excited 1Au(S1) trans‐glyoxal (in collisions with H2, at a collision energy of 80 meV) are reported. These results are used to assess the influence of sequential collisions on a recent experiment on glyoxal +H2. For ‖ΔK‖>3, the cross sections for rotationally inelastic scattering σ(00,K=k→00,K’=K+ΔK) depend exponentially on (ΔK)2 (and not on the energy difference between the initial and final states), which shows that the rotationally inelastic scattering is dominated by angular momentum transfer rather than by energy transfer. Taking into account sequential collisions leads to a substantial improvement in the agreement between the calculated and experimental values of the rotationally resolved cross sections for excitation of the lowest frequency ν7 torsional mode.

Results of quantum calculations on rotationally and vibrationally inelastic scattering of 1Au(S1) trans‐glyoxal by H2,He, and Ar(E=80 meV) are presented. For scattering of 00 glyoxal and 72 glyoxal by H2, a quantitative comparison with a recent crossed beam experiment is made. The calculated cross sections for rotationally inelastic scattering are in good agreement with the experimental values, and the trend that σ(72, k=0→72, k’) falls off faster with k’ than σ(00, k=0→00, k’) is reproduced. Our calculations do not reproduce the experimental finding that, for the initial 72 level, the cross sections for the Δv7=−1 and Δv7=+1 transitions are nearly identical. The calculations on 72 glyoxal + He and Ar show important differences with 72 glyoxal + H2 in the competition of rotational excitation with vibrational excitation. Model calculations also presented here yield some interesting trends in the k’ dependence of the cross sections σ(00, k=0→x1, k’) on the vibrational mode x excited.

Using the Monte Carlo classical trajectory (CT) method and the azimuthal close‐coupled, infinite‐order sudden (ACC‐IOS) method, we have calculated cross sections for rotational excitation of S1 trans‐glyoxal by H2 at E=80 meV. The cross sections σ(k=0, j→k’) calculated with the CT method are nearly independent of j. The classical values of σ(k=0, j=5→k’) are in good agreement with the quantum values of σ(k=0→k’) for 2≤k’≤12, although the quantum calculations show a slight preference for odd Δk transitions which is not found in the CT calculations. Both the CT results and the ACC‐IOS results are in good agreement with results obtained in a recent crossed beam experiment. Rotational excitation to high k’ (k’=11,12) occurs by collisions of H2 with one of the H atoms of glyoxal, and the initial value of the orbital angular momentum approximately equals the final value of k in such collisions. Since backward scattering is dominant in collisions leading to high k’, angular momentum constraints alone cannot expl...

Using the Monte Carlo classical trajectory method, we have calculated cross sections for complex formation and complex lifetimes for glyoxal–helium collisions at low relative translational energies (