Vibrational Energy Transfer and De-excitation in the HF, DF, HF–CO2, and DF–CO2 Systems

Abstract

The laser excited fluorescence method has been employed to determine the key rate constants for energy transfer and deactivation processes in the HF, DF, $\mathrm{HF}–{\mathrm{CO}}_2$ , and $\mathrm{DF}–{\mathrm{CO}}_2$ chemical laser systems at a temperature of 350°K. The self‐deactivation rates for HF $\text{(v=1)}$ and $\mathrm{DF}\text{(v=1)}$ molecules by ground state molecules were found to be $k_{\mathrm{HF}–\mathrm{HF}}{\text{=5.25 ± 0.30 × 10}}^4\hspace{0.17em}{\sec }^{\text{−1}}\mathrm{·\; \hspace{0.17em}}{\mathrm{torr}}^{\text{−1}}$ and $k_{\mathrm{DF}–\mathrm{DF}}{\text{= 2.0 ±\hspace{0.17em}0.2 × 10}}^4\hspace{0.17em}{\sec }^{\text{−1}}\mathrm{·\; \hspace{0.17em}}{\mathrm{torr}}^{\text{−1}}$ , respectively. The measured rates of $\mathrm{V\; \to \; V}$ transfer from $\mathrm{HF}\text{(v=1)}$ and $\mathrm{DF}\text{(v=1)}$ to the CO₂(00⁰1) state were $k_{\mathrm{HF}–{\mathrm{CO}}_2}{\text{= 3.7 ± 0.3 × 10}}^4\hspace{0.17em}{\sec }^{\text{−1}}\mathrm{·\; \hspace{0.17em}}{\mathrm{torr}}^{\text{−1}}$ and $k_{\mathrm{DF}–{\mathrm{CO}}_2}{\text{= 17.5 ± 2.5 × 10}}^4\hspace{0.17em}{\sec }^{\text{−1}}\mathrm{·\; \hspace{0.17em}}{\mathrm{torr}}^{\text{−1}}$ . The respective deactivation rates of CO₂(00⁰1) by ground state HF and DF were determined to be $k_{{\mathrm{CO}}_2–\mathrm{HF}}{\text{= 3.6 ± 0.3 × 10}}^4\hspace{0.17em}{\sec }^{\text{−1}}\mathrm{·\; \hspace{0.17em}}{\mathrm{torr}}^{\text{−1}}$ and $k_{{\mathrm{CO}}_2–\mathrm{DF}}{\text{= 1.9 ± 0.4 × 10}}^4\hspace{0.17em}{\sec }^{\text{−1}}\mathrm{·\; \hspace{0.17em}}{\mathrm{torr}}^{\text{−1}}$ . The large rates for these processes can be attributed to energy transfer to rotation under the influence of a sizable attractive (hydrogen bonded) intermolecular potential well and enhanced repulsion at close range.