The mean adsorption lifetime tgr;3of Cs+on tungsten has been measured in the 1000deg;mdash;1200deg;K temperature range, using a pulsed beam technique. Under conditions of low surface coverage and with either Cs or CsI as beam materialstgr;3equals;lpar;1.0plusmn;0.5rpar;times;10minus;12explsqb;lpar;23thinsp;600plusmn;500rpar;sol;Trsqb;secwas obtained. The heat of desorption can be calculated as the energy required to remove an isolated Cs+ion from the surface of an electrical conductor. The presence of an adsorbed contaminating layer, arising from residual vacuum gases, decreased the Cs+mdash;W binding energy by 0.5 eV and increased the prehyphen;exponential factor by about two orders of magnitude. Anomalous results were obtained when CsCl was used for a beam material, suggesting a reaction between the surface tungsten atoms and atomic chlorine.
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