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The kinetics of adsorption with long-range interaction between adsorbed particles

Published online by Cambridge University Press:  24 October 2008

J. S. Wang
Affiliation:
Fitzwilliam House

Extract

The rates of condensation and evaporation of adsorbed particles when they interact with long-range forces are deduced from kinetic considerations, including also the case of adsorption of diatomic molecules with dissociation. The rate of evaporation is compared with experiment, and the variation of the dipole moment with θ required to make the theory agree with experiment is discussed.

Finally the formulae for the rates of condensation and evaporation are applied to the problem of the diffusion of gases through metals, and it is found that for the processes considered the effect of interaction does not alter the conclusion arrived at in an earlier paper concerning the diffusion equation at small p and at large p.

Type
Research Article
Copyright
Copyright © Cambridge Philosophical Society 1938

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References

* Wang, J. S., Proc. Cambridge Phil. Soc. 32 (1936), 657–62.CrossRefGoogle Scholar This is referred to as I.

Roberts, J. K., Proc. Roy. Soc. A, 161 (1937), 141–53.CrossRefGoogle Scholar

* Wang, J. S., Proc. Cambridge Phil. Soc. 34 (1938).Google Scholar This is referred to as III.

Cf. Peierls, R., Proc. Roy. Soc. A, 154 (1936), 207–22.CrossRefGoogle Scholar

* See Wang, J. S., Proc. Roy. Soc. A, 161 (1937), 130,CrossRefGoogle Scholar equations (8) and (9). This paper is referred to as II.

* Another way of comparing theory with experiment would be to start by assuming a given law for the variation of the interaction energy with θ and to deduce the corresponding evaporation, rates, but owing to the high sensitivity of the interaction energy to the lattice distance it cannot be accurately calculated from the experimental data for the dipole strength (we suppose that we are considering the case of dipole interaction), and therefore this procedure is not practicable.

Bosworth, R. C. L., Proc. Roy. Soc. A, 162 (1937), 3249.CrossRefGoogle Scholar

* See Fowler, R. H., Proc. Cambridge Phil. Soc. 32 (1936), 144–51.CrossRefGoogle Scholar

See Peierls, , Proc. Cambridge Phil. Soc. 32 (1936), 471–6.CrossRefGoogle Scholar

Langmuir, I., J. American Chem. Soc. 54 (1932), 2824.Google Scholar See also Bosworth, R. C. L. and Rideal, E. K., Proc. Roy. Soc. A, 162 (1937), 26.Google Scholar

§ J. S. Wang, III.

The values of ξ1 corresponding to θ = 0, ½ 1 are 0, ∞ respectively, where

in the case of a quadratic lattice and in the case of a hexagonal lattice. It is easy to prove that the function f1) satisfies the relation Hence at θ = ½ we have which is the same as at θ = 1.

* Bosworth, R. C. L. and Rideal, E. K., Proc. Roy. Soc. A, 162 (1937), 26.Google Scholar

* J. S. Wang, II.

J. S. Wang, I.

* The rates (ii) and (iii) are derived under the assumption that the gas atoms immediately inside the metal surface are practically free, or more exactly, if they are bound with an energy χi per atom, that χi is less than χd − χ.