ENERGY TRANSFER AND THERMALIZATION OF THE VIBRATIONAL ENERGY IN GASES AS A FUNCTION OF THE TEMPERATURE

Author Institution: Laboratorie de Spectroscopie Mol\'{e}culaire II, Universite de ParisWe have measured, using a laser-excited vibrational fluorescence method, between 300 K and 1000 K: The rate constants associated with the deactivation by collision of $CO_{2}$ and $N_{2}O$ excited on the $00^{0} 1$ vibrational level. The rate constants for nearly resonant vibrational energy exchange between $N_{2}O$ and $N_{2}$ or CO; the probabilities per collision of vibrational energy transfer were computed by a theory involving long-range intermolecular forces and compared to the experimental results

VIBRATIONAL RELAXATION IN THE BINARY GASEOUS MIXTURES HCℓ−CO2HC\ell-CO_{2} AND HCℓ−N2OHC\ell-N_{2}O

Author Institution: Laboratoire de Spectronomie Moleculaire, Universit\'e de Paris VI, 4, Place Jussieu - Tour 13Vibrational relaxation rates for gaseous mixtures $M-HC\ell$, with $M = CO_{2}$ or $N_{2}O$, in which vibrational energy transfer can occur from the $(00^{\circ} 1)$ level of M to the v = 1 level of $HC\ell$, has been measured as a function of the temperature using the laser-induced vibrational fluorescence technique. The relaxation processes which must be considered are: - the V-V transfer process: \begin{eqnarray*} &&M(00^{\circ }1)+ HC (v=0)\begin{array}{c}^{k}M-HC\ell\\ \rightleftharpoons\\ ^{k}HC\ell-M\end{array}M(00^{\circ}0)+ HC\ell(v=1)+ \Delta E=he\Delta\nu\\ &&with\ \Delta\nu=-537\, cm^{-1} for\ CO_{2}, -663\, cm ^{-1}\ for\ N_{2}O \end{eqnarray*} - the V-TR de-excitation processes: \begin{eqnarray*} M(00^{\circ}1)+ HC\ell(or M)\stackrel{k^{HC\ell}_{M}}{(o\vec{r}\; k_{M})}M(mn^{\ell}0)+HC\ell (or \; M)\\ HC\ell(v=1)+ M(or\; HC\ell)\stackrel{k^{M}_{HC\ell}}{(o\vec{r}\; k_{HC\ell})}HC\ell(v=0)+M(or \; HC\ell) \end{eqnarray*} For most of the systems in which near-resonant V-V transfers occur, the V-TR de-excitation rates are negligible compared to the V-V transfer rates. But this is not the case for the M-HC$\ell$ systems considered in this work. The de-excitation rates $k^{M}_{HC\ell}$ and $k^{HC\ell}_{M}$ are of the same order of magnitude as the V-V transfer rates $k_{HC\ell-M}$ and $k_{M-HC\ell}$ respectively. In order to determine separately all these rates, relaxation measurements have been performed by exciting either H to the $(00^{\circ} 1)$ level or $HC\ell$ to the v = 1 level, and measuring the relaxation rates versus the molar fraction of the gas excited by laser. The results are discussed and compared with the values of the rates calculated by using a Morse potential as the intermolecular potential, and according to a semi-classical method in which a vibration-rotation exchange is assumed