Surface Interactions of Iodine Vapor with Tungsten

Abstract

The interactions of iodine vapor with a clean tungsten surface were studied by first adsorbing the iodine on the tungsten ribbon and then thermally desorbing the adlayer. The composition of the desorption products was determined with a time-of-flight mass spectrometer. No evidence is found for the formation of surface compounds. Only iodine atoms and, at higher coverages, iodine molecules populate the surface. Both desorptions are first order, and the most tightly bound atom state has a desorption energy of ∼80 kcal. A second, lower-energy atom state is populated at higher coverages. An estimate of the iodine molecule desorption energy gives ∼40 kcal.