Interaction between vibrationally excited diatomic and triatomic molecules

A theoretical analysis is made of the vibrational interaction of diatomic molecules with combination levels of triatomic molecules. Allowance is made for the V-V and V-T processes, and for the intramolecular exchange. Simple expressions are obtained for the relationship between the vibrational temperature of the ν 3 mode of a triatomic molecule and the vibrational temperature of a diatomic molecule under quasiequilibrium conditions. It is shown that in some cases the ν 3 mode may be heated by the energy stored in the diatomic molecule vibrations. Estimates of this effect are obtained for the HF-CO 2 , DF-CO 2 , D 2 -CO 2 , and CO-CS 2 systems. Experimental measurements are reported of the gain in a supersonic D 2 -CO 2 stream for the 00 0 1–10 0 0 transition. The experimental values of the gain show that the ν 3 mode of CO 2 is heated in the D 2 -CO 2 system by the energy stored in the vibrations of D 2 .