Investigation of quantum effects on vibrational excitation of CF3Br scattering from graphite

Mixed Quantum−Classical Scattering Dynamics of CF3Br

“…The almost total lack of effects due to a quantum treatment of the vibrations is in agreement with our previous 2D results …”

“…The agreement between classical and quantum mechanical energy transfer (Figures and and Table ) for frequencies in a range from 303 cm -1 to 1085 cm -1 strongly supports the use of classical mechanics for the 3D reduced dimensionality model. Furthermore, as implied by Figure and Table this is likely to carry over to the full 9D treatment which is in fair agreement with experimental results. , Out of the nine vibrations the three with frequencies below 353 cm -1 account for 74% of the excitation (evenly distributed with ca. 28 meV per vibration).…”

“…The translational energy was 2.0 eV (corresponding to 1615 m/s) and the initial velocity vector was along the surface normal. The initial orientations are the same as in ref (ϑ is the angle between the C−Br vector and the surface normal):…”

“…The present reduced dimensionality calculations are carried out in terms of the distance between Br and the center of mass of CF 3 ( z 1 ), the distance between C and the plane of the F atoms ( z 2 ), and the distance from the Br− C axis to the F atoms ( y ), see Figure . As in our previous work with the umbrella model, C 3 v symmetry is preserved, but now also the C−F distance is allowed to change.

1 Definition of the coordinates used in the reduced dimensionality calculations.

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“…The observed sensitivity of the vibrational excitation to the methods of initialization and analysis, on the other hand, indicate that quantum effects still may play a role. In a recent paper we studied the system using a reduced dimensionality treatment including the C−Br stretch and the CF 3 umbrella motion . Within this 2D approximation we could afford to carry out wave packet calculations to be compared with the corresponding classical treatment.…”