Abstract
RECENT work1,2 has shown that when certain hydrides are adsorbed on tungsten filaments at low pressures, and temperatures around 1,750° K., part is apparently desorbed as a negative ion, and a residual hydrogen atom is left bound to the tungsten surface. At the low surface coverages prevailing under the conditions of experiment, the migration of these residual hydrogen atoms to adjacent sites is relatively slow, so that the process of desorption is energetically isolated from that giving rise to negative ions. The approximate strength of the tungsten–hydrogen bond formed in this process has been put at 73.5 kcal./mole (refs. 3 and 4) based on measurements at room temperature, and this value was used in deducing the mechanism outlined above, but as an order of magnitude only. Several results have now been obtained, and the argument may be inverted, to use these results in conjunction with established electron affinities and heats of atomization, to deduce the strength of the W—H bond at these elevated temperatures. Briefly, the apparent electron affinity, E′, is related to the true electron affinity, E, the heat of atomization of the substrate, D, and the tungsten–hydrogen bond energy Q r by the relation :
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References
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PAGE, F. Heat of Adsorption of Hydrogen on Tungsten at Elevated Temperatures. Nature 188, 1021 (1960). https://doi.org/10.1038/1881021a0
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DOI: https://doi.org/10.1038/1881021a0
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