Accession Number : AD0682373

Title :   THE INTERACTION OF LOW-ENERGY ATMOSPHERIC IONS WITH CONTROLLED SURFACES.

Descriptive Note : Final rept. 1 Apr 66-1 Apr 68,

Corporate Author : TORONTO UNIV (ONTARIO) INST FOR AEROSPACE STUDIES

Personal Author(s) : Prince,R. H. ; French,J. B.

Report Date : DEC 1968

Pagination or Media Count : 130

Abstract : The ejection of electrons associated with the Auger Neutralization of N2(+), H2(+), and N(+) ions at the (100) face of a tungsten single crystal and a polycrystalline molybdenum surface was studied for the first time in the energy range 10 to 30 eV under controlled surface conditions. The dependence of the electron yields and energy distributions on ion energy was investigated in detail for the above ion-surface combinations. The combination of ultrahigh vacuum techniques to lengthen the time required to reach adsorption equilibrium after flashing, and special guarding and analog data-reduction techniques to reduce instrumentation time response, permitted the study of transient adsorption effects as well as the more usual equilibrium studies. Surface contamination was inferred using the measurement of work function which is sensitive to surface adsorption levels. The fact that the electron yields for diatomic ions was considerably lower than those for the inert gas ions treated well by Hagstrum's theory led Propst and Luscher to propose that the neutralized ion may be vibrationally excited as a consequence of the interaction. In the present report, a quantitative calculation was performed in this low-energy regime for which kinetic broadening effects may be safely neglected. The simplified theoretical treatment provides good agreement with Propst and Luscher's data for 50 eV N2(+) ions on polycrystalline tungsten, using a value of the escape parameter f (the anisotropy of excited metal electrons) taken from Hagstrum's work. A slightly larger anisotropy permits good agreement with the present data for the (100) face of a tungsten single crystal. (Author)

Descriptors :   (*ION BEAMS, RAREFIED GAS DYNAMICS), (*TUNGSTEN, ION BOMBARDMENT), (*MOLYBDENUM, ION BOMBARDMENT), SINGLE CRYSTALS, CRYSTAL DEFECTS, CONTAMINATION, IONS, NITROGEN, HYDROGEN, DIATOMIC MOLECULES, MICROSCOPY, X RAY DIFFRACTION, MASS SPECTROSCOPY, CANADA, SECONDARY EMISSION, NEUTRALIZATION

Subject Categories : Atmospheric Physics
      Atomic and Molecular Physics and Spectroscopy

Distribution Statement : APPROVED FOR PUBLIC RELEASE