THE ANGULAR DISTRIBUTION OF VAPOR FLOWING FROM A KNUDSEN CELL
Abstract
Equations for the spatial distribution and total effusion flow of molecules effusing from a Knudsen orifice by both surface diffusion and vapor transport are developed. The equations are exact, within the assumptions of the model, for knife-edge orifices with small L/R. The equations are only approximate for large L/R. The resultant theoretical predictions agree very well with the experimental observations of Gunther, even for the approximate cases of large L/R. The quantity E, containing both the surface diffusion coefficient Ds and the desorption energy Gds, was found to be equal to 1/20 cm for Gunther's experiments. Consideration of the approximate methods of estimating equilibrium vapor pressures using Knudsen cells indicates that, if surface diffusion and orifice focussing corrections are neglected, the target intercept method should give more accurate results than the total weight loss method for large L/R ratios and vice-versa. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1962
- Accession Number
- AD0289397
Entities
People
- J.p. Hirth
- V. Ruth
Organizations
- Ohio State University