Lithium adsorption on hot oxygen covered tungsten surfaces

The mean residence times τ of lithium particles on oxygen covered tungsten surfaces were measured accurately over a wide temperature range (1200 < T < 1900 K) by the beam modulation technique with a lock-in analyzer. A predominant monocrystalline W(100) structure was obtained by recrystallization of a polycrystalline tungsten ribbon. The residence time was determined as a function of the oxygen coverage θ and the temperatureT of the surface. The desorption energy l and the preexponential factor τ₀, calculated from the Arrhenius equation, are not only dependent on the amount of adsorbed oxygen but also on the oxygen structure. Apparently the desorption parameters l and τ₀ are correlated. An increasing desorption energy l is connected to a decreasing “vibration period” τ₀ whereby the influence on the residence time is partly compensated.