Vibrational Relaxation of Hydrogen

The rates of vibrational relaxation of D₂ and HD have been studied by laser‐induced vibrational fluorescence technique. The relaxation times of D₂/HCl, HD/HCl, D₂/H₂/HCl, and D₂/HD/HCl mixtures at 296°K show cross sections of $\mathrm{V}\mathrm{\to \; T}$ , R energy transfer as $$\begin{array}{c}{\sigma }_{{\mathrm{D}}_2–{\mathrm{D}}_2}{\text{=1.4 ± 0.1 × 10}}^{\text{−22}}\hspace{0.17em}{\mathrm{cm}}^2,\\ {\sigma }_{{\mathrm{D}}_2–{\mathrm{H}}_2}{\text{=1.4 ± 0.1 × 10}}^{\text{−21}}\hspace{0.17em}{\mathrm{cm}}^2,\\ {\sigma }_{{\mathrm{D}}_2–\mathrm{HD}}{\text{=8.2 ± 1.0 × 10}}^{\text{−22}}\hspace{0.17em}{\mathrm{cm}}^2,\\ {\sigma }_{\mathrm{HD}–\mathrm{HD}}{\text{=6.9 ± 0.8 × 10}}^{\text{−22}}\hspace{0.17em}{\mathrm{cm}}^2,\\ {\sigma }_{\mathrm{HCl}–{\mathrm{D}}_2}{\text{=4.0 ± 0.4 × 10}}^{\text{−21}}\hspace{0.17em}{\mathrm{cm}}^2,\\ {\sigma }_{\mathrm{HCl}–\mathrm{HD}}{\text{=1.7 ± 0.2 × 10}}^{\text{−20}}\hspace{0.17em}{\mathrm{cm}}^2.\end{array}$$ Cross section for $\mathrm{V}\to \mathrm{V}$ energy transfer from HCl to HD as $${\sigma }_{\mathrm{HCl}–\mathrm{HD}}^{\mathrm{v\; \to \; v}}{\text{=2.0 ± 0.2 × 10}}^{\text{−20}}\hspace{0.17em}{\mathrm{cm}}^2.$$ Comparison of vibrational relaxation rates among hydrogen isotopes and direct correlation between high temperature shock tube results and room temperature data reveal the importance of both rotational and translational motion in the process of vibrational energy transfer of hydrogen.