Interchange of Translational, Rotational and Vibrational Energy in Molecular Collisions

The change in internal energy of molecules upon collisions has been analysed. Formulae, (26) to (27-C), for the effective cross section of inelastic collisions have been obtained as functions of known properties of the molecules, subject to certain conditions. These conditions are: the atoms which come into contact during collision must belong to the first row of the periodic table; the vibrational quantum numbers which suffer a change must be small.Vibrational quantum numbers have a marked reluctance to change during collisions at room temperature. The probability that a N₂ molecule in its first excited vibrational state transfer its energy to He in a head on collision is 0.0⁷6. The probability that another N₂ molecule absorb this energy is 0.0⁴4. A lack of resonance of 0.01 volt can decrease the effective cross section by a factor of 0.02.Rotational quantum numbers change readily except in unusual cases.