Temperature Dependence of Intramolecular Vibration→Vibration Energy Transfer in CO2

Abstract

Intramolecular vibration‐to‐vibration energy transfer cross sections have been measured for gaseous CO₂ with one quantum of asymmetric stretching energy. Data were obtained using the laser‐excited vibrational fluorescence method. Results are given over the temperature range 298–800°K for the collision partners n‐H₂, ³He, ⁴He, Ne, Ar, Kr, and Xe, and for p‐H₂, HD, and D₂ at 298°K. All cross sections increase with temperature; those for the rare gases depend only weakly on reduced mass. The cross sections for hydrogen are much larger than those for helium, and increase sharply as the reduced mass decreases. The simple form of transition probability as a function of velocity and intermolecular potential used in most theories of vibration–translation energy transfer does not adequately account for these results. Since equal cross sections are observed for n‐H₂ and p‐H₂, it is unlikely that energy is transferred into rotation of H₂.