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 $ε / k = 85°K$ and $σ′H,H2 = 2.32 Å$⁠. Comparisons are made with values derived from viscosity data and with theoretical calculations.