Accession Number:

ADA076972

Title:

More on the Acoustical Method for Measuring Energy and Tangential Momentum Accommodation Coefficients.

Descriptive Note:

Technical rept. 1978-1979,

Corporate Author:

MISSISSIPPI UNIV UNIVERSITY DEPT OF PHYSICS AND ASTRONOMY

Personal Author(s):

• Shields,F. Douglas

Report Date:

1979-11-01

Pagination or Media Count:

21.0

Abstract:

Additional measurement sof the energy EAC and tangential momentum accommodation coefficients TMAC of He and Ne on polycrystalline tungsten have been made using an acoustic technique previously reported. The measurements were made after the tungsten surface had been exposed to the atmosphere and after it had been flashed in a vacuum at 1240, 1460, 1770 and 2000 K. Three stable, reproducible surfaces were detected. These have been associated with an atomic oxygen film, upper molecular oxygen film, and an unknown film produced by atmospheric exposure. Comparison with molecular beam scattering experiments indicates that TMAC corresponds to the fraction of molecules scattered diffusely from polycrystalline surfaces and EAC to the diffuse fraction from single crystal surfaces. Author

Descriptors:

• *SINGLE CRYSTALS
• *MOLECULAR BEAMS
• *SURFACE PROPERTIES
• *ACOUSTIC VELOCITY
• SCATTERING
• HELIUM
• NEON
• TUNGSTEN
• MOMENTUM

Subject Categories:

• Acoustics
• Crystallography
• Nuclear Physics and Elementary Particle Physics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE