Research was carried out into fluctuations in the ion thermo-emission currents (of the 5 alkali metals) from W surfaces. The activation energy for Rb surface diffusion was deduced to be equal 0.44eV. This so-called noise was generated as a result of adsorbate density fluctuations. The latter caused random changes in the work function, which itself influenced the intensity of the emitted ion current. The methods which were used made it possible to determine the ion desorption energy and the surface diffusion energy for the alkali metals. It was suggested that the activation energy for surface diffusion was related to the ionic radius of the alkali metal by:

E (eV) = 0.88 - 0.33R(วบ)

L.Gladyszewski: Surface Science, 1990, 231[1-2], 120-4