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Author Pasternak, R. A. ♦ Wiesendanger, H. U. D.
Sponsorship USDOE
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword CHEMISTRY ♦ ADSORPTION ♦ HYDROGEN ♦ INTERACTIONS ♦ MOLYBDENUM ♦ NITROGEN ♦ PRESSURE ♦ REACTION KINETICS ♦ SURFACES ♦ TEMPERATURE
Abstract Adsorption and desorption studies, using flash-filament and ion gauge techniques, gave information on surface coverages, sticking probabilities, atom formation, and surface mobilities for the interaction of gases with a molybdenum ribbon. For hydrogen, saturation surface coverages were independent of pressure (10/sup -//sup 8/ --10/sup -//sup 5/ mm Hg), within experimental errors, but depended strongly on temperature (225 to 500 deg K). Adsorption below 320 deg K proceeded in two steps. Two layers were successively adsorbed and completed at 320 deg and 225 deg K, respectively; each contained close to two hydrogen atoms per surface molybdenum atom. The sticking probability was 0.35; it remained constant during the formation of the first layer. At about 700 deg K, no measurable amounts of hydrogen were retained on the ribbon surface, but the kinetics of atom formation above l200 deg K suggested that traces of hydrogen might be adsorbed at much higher temperatures. Finally, adsorbed hydrogen was readily replaced by other gases, such as nitrogen, even at room temperature. For the absorption of nitrogen, the saturation surface coverage decreased only about 30% from 225 to 710 deg K; its value at room temperature was about one nitrogen atom per surface molybdenum atom. The initial sticking probability, in the same temperature range, decreased from 0.7 to 0.2. (auth)
ISSN 00219606
Educational Use Research
Learning Resource Type Article
Publisher Date 1961-06-01
Publisher Department Stanford Research Inst., Menlo Park, Calif.
Journal Journal of Chemical Physics
Volume Number 34
Organization Stanford Research Inst., Menlo Park, Calif.


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