Experimental Measurements of the Diffusion Coefficients of H Atoms in H2 and in H2–He and H2–Ar Mixtures

The catalytic sink technique previously described was used to measure the diffusion coefficients of H atoms in H₂ over the temperature range 202°–364°K and in H₂–He and H₂–Ar mixtures at 275°K. The rigid‐sphere collision diameters of H atoms in H₂, He, and Ar were 1.89, 1.94, and 1.84, respectively. However, the temperature dependence of the H–H₂ diffusion coefficients does not fit the rigid‐sphere equation but can be represented by the use of the Lennard‐Jones parameters $\text{ε\hspace{0.17em}/\hspace{0.17em}k\hspace{0.17em}=\hspace{0.17em}85°K}$ and ${\mathrm{\sigma \prime }}_{{\mathrm{H,H}}_2}\text{\hspace{0.17em}=\hspace{0.17em}2.32 Å}$ . Comparisons are made with values derived from viscosity data and with theoretical calculations.