Vibrational relasatioo of CO2 by Hz0 has been studied theoretiully. Earlier theoretical works are critically analyzed.
A new mechanism of V-R-T interaction is put forxvard and a functional equation for the probability factor is obtained. Collisions of CO2 with H-J 0 adsorbed on a solid surface are also considered.
Experimental
and theoretical research into the vibrational relaxation of CO2 upon collisions with atoms and molecules and with solid surfaces has been carried out with in&easing vigour for several decades. Special attention is being paid to this process because of the development of the CO, gas laser technique. Vibrational-translational (V-T) energy transfer in CO~(U& Hz0 collisions CO,(OlO) f Ii,0 = CO,(OOO) + H,O + 667 cm-' (1) being of great importance for the deactivation of low 'ker ievels has been considered in a number of studies [l-19].
Fundamental theoretical and experimental problems are as follows: (I) to obtain the vibrational relaxation time 7, (2) to determine the mechanism of vibrational energy transfer and to calculate the probabilities of various elementary processes and to explain isotopic effects (increasing r when replacing DzO for H20), (3) to derive the relaxation equations for vibrational energies ei and temperatures.Ti of different vibrational modes q-. r"r COa, the notion of a vibrational temperature (that is, the supposition of the Boltzmann distribution) may be used as mentioned in ref.
[%O] only if one assmcs that T1 = T2. WI =: Z& (wi is the frequency of the mode ui)-This is due to the fact that in the harmonic approximation, 'the kergies of the states described by harmonic w&functions 1020) and ! 100) and al?0 fO30? zd ! 110) are almost coincident, thus providing for corisiderable anharmonicirj, or a full mixing of these-states (therms reso&nce)*. Anharmo-* Therefork, roughly speaking, a comparable contribution to V-T relaxation in the combined mode 1112 is made both by processes (nm0) * (nm-IO) and (nm0) + (n-lm+lO).