Of nitrogen on tungsten

The adsorption of nitrogen on tungsten 51) was the first nitrogen system to be studied (Fig. 12) by XPS subsequently nitrogen interaction with iron was studied (52, 53), and two distinct N(ls) peaks were observed at 80 K, one at about 405 eV and the other at 400 eV. At room temperature with both single crystals and polycrystalline iron surfaces only a single peak is... 

The heat of adsorption of nitrogen on tungsten at room temperature was found to be 95,000 calories per mole and constant over the whole fraction of the surface which it will cover—that is, about 60%. The adsorption is instantaneous. In Fig. 21 is [shown the heat of adsorption of hydrogen on a tungsten surface covered 60% with nitrogen. 

IV. The Adsorption of Nitrogen on Tungsten as Deduced from Ion Gauge and... 

Fiq. 13. Schematic diagram of experimental system used to study the adsorption of nitrogen on tungsten. 

Figure 1. Comparison of data on sticking probability, S, of nitrogen on tungsten...

Davis obtained a value of Ae of 12.68 kcal./mole from the observed chemisorption rate of nitrogen on tungsten and compared it with a value of Ae of 10 kcal./mole derived according to equation (3). A calculation from the relation that Ae is 10 kcal. - - %RT of the rate by means of equation (6) leads to the result that T is 7.1 X 10 . as shown in Table I. The initial rate of chemisorption calculated on the basis of an activation energy deduced from the observed rate is not reliable because the rates... 

King and co-workers [45—48] have examined the applicability of these kinetic models to the adsorption of nitrogen on tungsten single crystal planes. 

The relative concentration of nitrogen on the different crystal planes at room temperature may be affected by mobile chemisorbed material if nitrogen chemisorbed on tungsten is mobile at room temperature. While data on the mobility of nitrogen on tungsten are not available, the field-emission behavior of this same tungsten tip toward oxygen and carbon... 

Table 3.11. Adsorbed states of nitrogen on tungsten surfaces...

Values of X for hydrogen peaks on individual crystal planes of tungsten and molybdenum were found to be about 1-3 kcal/monolayer (101). A stronger dependence of Ed and n, resulted for nitrogen on tungsten (98). 

Fig. 18. Variation of the activation energy with amount adsorbed for nitrogen on tungsten.

For the benefit of those readers who might feel that we are basing far-reaching conclusions on the results of one system, namely nitrogen on tungsten, we add that exploratory experiments similar to those described... 

The same analysis was performed on the nitrogen peak but, as the N signal on the surface was strong, the first two spectra were not eliminated. The spectra and the relative concentration matrix show three principal components (Figure 26.3(c)). One can underline the complementarity of the concentration profiles of nitrogen and tungsten. 

The Calculated and Observed Fraction of Surface Covered for Nitrogen on Tungsten at... 

King DA, Wells MG (1972) Molecular beam investigation of adsorption kinetics on bulk metal targets nitrogen on tungsten. Surf Sci 29 454... 

However, this view seems contradicted by additional evidence. Jungers and Taylor (43) and also Barrer (44) observed a kinetic isotope effect in the decomposition rates of ammonia and its deuterocompounds on a tungsten surface NHg decomposed more rapidly than NDg. This isotopic effect of hydrogen cannot be explained by the saturated adsorption of nitrogen on the catalyst surface. 

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