Specific Features of Equilibrium Distributions

First of all it is essential to note that the quantities 3 R) mid Pp(R) determine the values of the flux density and pressure when the cell a is effectively occupied (b = 1). When 1 one has So 1 (ideal adsorbate), while for 6 1 Sq w 1 and effects of nonideality become significant. 

To simplify the analysis of (9.1.7) one may use an assumption that the first two layers are formed mainly by the substrate (model of chemisorption with precursor (Ceyer 1988)) and are characterized by different values of b, while for the upper layers (/9 3) b does not depend on P (BET-model)  

For ideal adsorbate (uq = 0), provided condition (9.2.1) is valid, the system (9.1.7) has a unique solution that can be written in the form 

Solution (9.2.4) is valid for arbitrary 62 values. In particular, when 62 1 the following simple approximation for 0 (a) with / 3 is useful 

For nonideal adsorbate (vq / 0) different situations are possible. Under the condition 

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