Sticking coefficient of oxygen

Figure 2.21. Initial sticking coefficient of oxygen, S0, on alkali modified Ru(001) as a function of alkali coverage.61 Reprinted with permission from Elsevier Science.

Schmidt, 1971), whereas for Mo(lQO) it is high. The sticking coefficient of oxygen on the open planes of metals up to and including Pt is high, whereas on Pt(lll) the dissociative adsorption is activated with a probability of only 0.1 (Refiner and Mullins, 1991). 

It is essential that oxygen was contained in subsurface Pt layers, dissolving there with increasing temperature. This oxygen, whose removal is extremely difficult, can affect the constants of surface reactions. For example, the initial sticking coefficient of 02 on the oxidized sample is S02 = 0.05, whereas for the Ir sample that was not exposed to oxygen we have Sq2 - 0.26 [78,106,142]. Since the literature lacks detailed information, our model does not account for this fact. 

Fic. 12. Computer simulations of the oscillatory range. Variation of the high and low CO pressure boundaries (at fixed p(h and 71 with the ratio a of (he sticking coefficients for oxygen on the nonreconstructed and reconstructed surfaces, respectively. (From Ref. 40.)... 

Using the exposure of 2 X 10 mm. Hg-min. as that corresponding to the completion of one monolayer, we may compute the average sticking coefficient. Taking the experimental result for the surface density of oxygen atoms as 4 X 10 atoms per unit area and 8.5 X 10 as the total number of atoms which strike unit area of the surface within the exposure, a sticking coefficient of about 5 X 10 is obtained. 

Figure 4.9. (a) The sticking coefficients of O2 on the flat Pt(l 11) and stepped Pt[14(l 11) x (111)1 crystal faces as a function of oxygen coverage [94]. (b) The sticking coefficients of nitrogen as a function of step density on various crystal faces of tungsten (95). 

---