The Accommodation Coefficient of Helium on Nickel

Abstract

The thermal accommodation coefficient of helium on gas-free "A" nickel was measured at the temperatures 90, 195, 273 and 369°K, and was found to be 0.048, 0.060, 0.071 and 0.077, respectively (±0.004). In the presence of the gas the accommodation coefficient rose rapidly to the equilibrium values 0.413, 0.423, 0.360 and 0.343, respectively (±0.012). Using the theory of A. F. Devonshire and the observed values of ${\alpha }_0$, calculations were made of the two constants of the interaction potential between a helium and a nickel atom. The results obtained were $\kappa =(0.75\mathrm{}\pm 0.05)\times {10}^8$ ${\mathrm{cm}}^{-1\mathrm{}}$ for the exponential decay constant, and $D=(430\mathrm{}\pm 60)$ cal./mol for the heat of adsorption of helium on nickel. At the two lower temperatures the thermal conductivity of "A" nickel was measured. The values obtained were (0.74±0.04) watt/${\mathrm{cm}}^2$/deg. at 90°K, and (0.71±0.04) watt/${\mathrm{cm}}^2$/deg. at 195°K.