Mobility and two-dimensional compressibility of Xe on the (110)plane of tungsten

Abstract

The diffusion of Xe on the (110) plane of tungsten has been studied as functin of coverage by the field emission current fluctuation method. At θ = 0.3, E dif = 1.1 ± 0.3 kcal, D 0 = 7 × 10 −8 cm 2s and atgq = 0.9, E dif = 1.1 ±0.3 kcal, D 0 = 10 −8 to 10 −9 cm 2/s. For θ = 0.5 no activation energy could be obtained because of anomalous temperature behavior of the apparent D values. The mean square fluctuations varied exponentially with temperature; the resultant energy parameters were 0.27 kcal for θ = 0.3 and 0.4 kcal for θ = 0.9, with the sign indicating repulsive interactions. For θ = 0.5 the value was −1 kcal, indicating apparently attractive interactions. It is speculated that the anomalous diffusion behavior and the sign of the interaction energy for θ = 0.5 correspond to incipient ordered phase formation of the Xe overlayer.