Deactivation of Vibrationally Excited Carbon Dioxide (ν3) by Collisions with Carbon Dioxide or with Nitrogen

The rate constants associated with the deactivation of vibrationally excited ${\mathrm{CO}}_2{\mathrm{*(\nu }}_3)$ by collision with either CO₂ or N₂ have been experimentally determined from 300°–1000°K by a laser fluorescence method. The reactions investigated were $${\mathrm{CO}}_2{\mathrm{*(\nu }}_3\mathrm{)+}{\mathrm{N}}_2\leftrightarrows {\displaystyle {lim}_{k_{\text{−5}}}^{k_5}}{\mathrm{CO}}_2+{\mathrm{N}}_2\mathrm{*,}$$ $${\mathrm{CO}}_2{\mathrm{*(\nu }}_3\mathrm{)+}{\mathrm{N}}_2\to {\displaystyle {lim}^{k_5}}{\mathrm{CO}}_2{\mathrm{*(\nu }}_1{\mathrm{,\; \nu }}_2\mathrm{)+}{\mathrm{N}}_2,$$ $${\mathrm{CO}}_2{\mathrm{(\nu }}_3\mathrm{)+}{\mathrm{CO}}_2\to {\displaystyle {lim}^{k_1}}{\mathrm{CO}}_2{\mathrm{*(\nu }}_1{\mathrm{,\; \nu }}_2\mathrm{)+}{\mathrm{CO}}_2,$$ $${\mathrm{N}}_2\mathrm{*+}{\mathrm{CO}}_2\to {\displaystyle {lim}^{k_7}}{\mathrm{CO}}_2{\mathrm{*(\nu }}_1{\mathrm{,\; \nu }}_2\mathrm{)+}{\mathrm{N}}_2,$$ where the asterisk denotes a vibrationally excited molecule, and the quantities in parentheses represent the specific excited modes of CO₂. The rate constant $k_5$ varies with temperature $T$ (°K) as ${\text{8.60\hspace{0.17em}×\hspace{0.17em}10}}^7{\mathrm{\hspace{0.17em}/\hspace{0.17em}T}}^{\text{3/2}}{\mathrm{torr}}^{\text{−1}}·{\sec }^{\text{−1}}$ . From 400°–1000°K the rate constant $k_1$ (per torr⁻¹ ·second⁻¹) varies with temperature as $${\log }_{10}{k}_1{\mathrm{\hspace{0.17em}=\hspace{0.17em}A\hspace{0.17em}-\hspace{0.17em}BT}}^{\text{−1\hspace{0.17em}/\hspace{0.17em}3}}$$ with $\text{A\hspace{0.17em}=\hspace{0.17em}6.79}$ and $\text{B\hspace{0.17em}=\hspace{0.17em}30.8}$ . From 300°–400°K the measured values of $k_1$ are greater than those corresponding to the above relation. The rate constant $k_6$ increases from a value of 110 torr⁻¹·sec⁻¹ at room temperature to a value of 2700 torr⁻¹·sec⁻¹ at 1000°K, but the variation of $k_6$ with temperature cannot be simply expressed. The rate constant $k_7$ was found to be negligibly small compared to the other rate constants.