Collisional deactivation of CF3I - a molecular dynamics simulation

The detailed mechanisms of re-vibrational energy transfer in collisions bet ween CF3I and argon or propane are investigated. Molecular dynamics simulat ions of collisions between a reactant CF3I molecule at energies from 50 to 200 kJ/mol with medium argon or propane at selected initial temperatures ar e interpreted in terms of ergodic collision limits. The intramolecular pote ntial used for CF3I is a Morse-stretch/harmonic-bend type function with par ameters fitted to equilibrium structure, normal mode frequencies and dissoc iation energies. Simple generic Buckingham type pair-potentials are used fo r intermolecular atom-atom interactions. Energy transfer is related to (i) geometry of collision, (ii) impact parameter, (iii) number of atom-atom enc ounters, (iv) average dynamical hardness of interaction at atom-atom collis ions, (v) number of minima in the center of mass separation and (vi) lifeti me of the collisional complex. The energy transfer in our molecular dynamic s calculations is compared with experimental results for the same colliders . The observed trends are interpreted in terms of detailed collisional mech anisms. Our results highlight the importance of rotational excitation and t he repulsive part of the intermolecular potential. (C) 1999 Elsevier Scienc e B.V. All rights reserved.