Kisliuk model

Figure IS. Relative sticking probabilities as a function of surface coverage according to the Kisliuk model [131, 132], For an explanation of K see text.

King and Wells [46] developed the Kisliuk model for dissociative adsorption to take account of ordering in the chemisorbed overlayer resulting from the existence of lateral interactions between chemisorbed species in nearest-neighbour positions, s could then be expressed as... 

K. Schdnhammer. On the Kisliuk Model for Adsorption and Desorption Kinetics. Surf Sci. 83-.L633 (1979). 

FIGURE 1.7. The Kisliuk model for "precursor" mediated adsorption. 

FIGURE 7.8 Time-dependent coverage determined from second harmonic generation (SFG) measurements (75) and fits based on Langmuir kinetics (dotted line, eq. [7.48]) and Kisliuk model (solid line, eq. [7.52]). (From Xiao, X. D., et al. 1996. Langmuir 12 235. With permission.)... 

Two distinct approaches have been used to model precursor state kinetics. (1) A successive site statistical model, introduced by Kisliuk [426] for adsorption and adapted by King [298] for desorption. (2) The chemical reaction kinetics approach, involving rate coefficients and the stationary state approximation, followed by Becker and Hartman [424], Ehrlich [425] and recently developed by Gorte and Schmidt [297] and Cassuto and King [421], It has recently been shown by Schon-hammer [427] and Cassuto and King [421] that the two approaches produce the same kinetic expressions. Variants of these models have... 

Although not explicitly stated, two different models have been used in the literature to describe the nature of the intrinsic precursor state not surprisingly, these model assumptions lead to different rate expressions. Kisliuk [426] and Gorte and Schmidt [297] assume that the intrinsic precursor occupies a single empty chemisorption site, while King and Wells [46] assume that is occupies an n.n. pair of empty chemisorption sites. 

The existence of a precursor state, where the incident atom or molecule is temporarily trapped in a shallow attractive potential, has been proposed by Kisliuk [34, 35]. In this precursor state, the molecule may visit several surface sites, one of which permits chemisorption. This model provides enough variables to explain the decrease of the sticking probability with increasing coverage and its complex temperature dependence, as found during the chemisorption of N2 on W(IOO), and O2 on W(llO) and Pt(lll). 

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