Understanding gas-surface interactions from direct force measurements using a specialized torsion balance

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The first comprehensive measurements of the magnitude and direction of the forces exerted on surfaces by molecular beams are discussed and used to obtain information about the microscopic properties of the gas-surface interactions. This unique approach is not based on microscopic measurements of the scattered molecules. The reduced force coefficients are introduced as a new set of parameters that completely describe the macroscopic average momentum transfer to a surface by an incident molecular beam. By using a specialized torsion balance and molecular beams of N{sub 2}, CO, CO{sub 2}, and H{sub 2}, the reduced force coefficients are determined from direct ... continued below

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11 p.

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Cook, S.R. & Hoffbauer, M.A. December 31, 1996.

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Description

The first comprehensive measurements of the magnitude and direction of the forces exerted on surfaces by molecular beams are discussed and used to obtain information about the microscopic properties of the gas-surface interactions. This unique approach is not based on microscopic measurements of the scattered molecules. The reduced force coefficients are introduced as a new set of parameters that completely describe the macroscopic average momentum transfer to a surface by an incident molecular beam. By using a specialized torsion balance and molecular beams of N{sub 2}, CO, CO{sub 2}, and H{sub 2}, the reduced force coefficients are determined from direct measurements of the force components exerted on surface of a solar panel array material, Kapton, SiO{sub 2}-coated Kapton, and Z-93 as a function of the angle of incidence ranging from 0{degrees} to 85{degrees}. The absolute flux densities of the molecular beams were measured using a different torsion balance with a beam-stop that nullified the force of the scattered molecules. Standard time-of-flight techniques were used to determine the flux-weighted average velocities of the various molecular beams ranging from 1600 m/s to 4600 m/s. The reduced force coefficients can be used to directly obtain macroscopic average properties of the scattered molecules, such as the flux-weighted average velocity and translational energy, that can then be used to determine microscopic details concerning gas-surface interactions without the complications associated with averaging microscopic measurements.

Physical Description

11 p.

Notes

OSTI as DE97007189

Source

  • 43. national symposium of the American Vacuum Society (AVS), Philadelphia, PA (United States), 14-18 Oct 1996

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  • Other: DE97007189
  • Report No.: LA-UR--97-1122
  • Report No.: CONF-961002--8
  • Grant Number: W-7405-ENG-36
  • Office of Scientific & Technical Information Report Number: 522750
  • Archival Resource Key: ark:/67531/metadc695620

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  • December 31, 1996

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  • Aug. 14, 2015, 8:43 a.m.

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  • Aug. 8, 2016, 8:37 p.m.

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Cook, S.R. & Hoffbauer, M.A. Understanding gas-surface interactions from direct force measurements using a specialized torsion balance, article, December 31, 1996; New Mexico. (digital.library.unt.edu/ark:/67531/metadc695620/: accessed August 20, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.