Accession Number:

AD0745034

Title:

Diffusion Theory for Adsorption and Desorption of Gas Atoms at Surfaces

Descriptive Note:

Corporate Author:

MASSACHUSETTS INST OF TECH CAMBRIDGE FLUID DYNAMICS RESEARCH LAB

Personal Author(s):

• Pagni, Patrick J.
• Keck, James C.

Report Date:

1972-05-01

Pagination or Media Count:

64.0

Abstract:

The time evolution of a nonequilibrium ensemble of gas atoms adsorbed on a solid surface is described. Adsorption and desorption rate constants and adatom adsorbed atom energy distributions are obtained in the steady state approximation from the appropriate master equation or an equivalent diffusion equation. Energy transition probabilities are obtain from a classical gas- surface collision model using an interaction potential composed of an oscillating harmonic repulsion and a stationary attraction. Applications include prediction of adsorption and desorption rate constants, sticking and accommodation coefficients, sublimation and condensation rates, and boundary conditions for the Knudsen layer.

Descriptors:

• *ADSORPTION
• *GASES
• *SURFACES
• CHEMICAL EQUILIBRIUM
• DIATOMIC MOLECULES
• DIFFUSION
• KINETIC ENERGY
• MATHEMATICAL MODELS
• POTENTIAL ENERGY
• REACTION KINETICS

Subject Categories:

• Physical Chemistry

Distribution Statement:

APPROVED FOR PUBLIC RELEASE