Abstract
Volatile products of the surface reaction between chlorine at room temperature and heated polycrystalline yttrium were identified and their formation rates were measured mass spectrometrically. At surface temperatures between 300° and 1700°K (yttrium melting point 1750°K) and chlorine pressures between 10—5 and 5×10—4 Torr, Cl, YCl2, and Cl2 were observed. No gaseous YCl or YCl3, was detected. The results are consistent with the presence of a strongly chemisorbed layer of chlorine atoms, stable over the entire temperature range, on which Cl2 adsorbs as Cl atoms. These either evaporate or react with YCl to form volatile YCl2. An activation energy of 55 kcal/mole for YCl2 evaporation is apparently associated with dissociative adsorption of chlorine on the chemisorbed Cl layer.

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