A MOLECULAR-DYNAMICS INVESTIGATION OF ENERGY-TRANSFER EFFICIENCY IN COLLISIONS OF DIATOMIC-MOLECULES

Diatomic collisional energy transfer has been studied with the aim of aiding the development of accurate representation of the activation-deactivation mechanism in gas phase reaction rate theory. We seek to determine the dependence of the energy transfer efficiency on the parameters describing the colliding molecules, i.e. mass, vibrational frequency, intermolecular potential and initial energy or temperature. While weak van der Waals type interactions give rise to very poor energy transfer efficiency scaling up the interactions to the strength of weak chemical bonds increases the energy transfer efficiency dramatically up to nearly statistical limit values. The dependence on mass and vibrational frequency is found to be weaker. The interaction strength is resolved into two factors, hardness of encounter and attractive strength. Varying these factors independently by a modification of the intermolecular atomic pair potential, both are found to contribute strongly to the observed energy transfer efficiency. Two temperatures, 160 and 1500 K, are considered and the sensitivity to the intermolecular potential is found to be distinctly greater at the lower temperature. The average energy transferred per collision [DELTAE] is obtained as a function of the internal energy of the target molecule at normal and high interaction strength.