ABSTRACT
The simplest collision process of atom and molecule is when no exchange of atoms and no electronic states of either atom or molecule are involved. The only energy exchange in such collisions is through the rotations and vibrations of molecules, which very often happen simultaneously. Therefore, strictly speaking, vibrations and rotations cannot be considered independently. In collisions of atoms and molecules there are essentially two ways in which the vibrational energy of the molecule can be changed: the kinematic mode and the dynamic mode. The first mode relies on the fact that when the atom hits the molecule the energy exchange occurs because of the direct impact of this atom with one of the atoms of the molecule. The dynamic mode is entirely due to the form of interaction between atom and molecule, prior to the short repulsive region.
