Accession Number : ADA133186

Title :   Experimental Studies of Secondary Ion Emission from Well-Characterized Surfaces.

Descriptive Note : Interim rept.,

Corporate Author : IRT CORP SAN DIEGO CA

Personal Author(s) : Palmer,R L

PDF Url : ADA133186

Report Date : May 1983

Pagination or Media Count : 25

Abstract : The emission of ions from surfaces has been investigated using a specially constructed secondary-ion mass and energy analyzer. The energy spectra of H-(D-) and H+(D+) secondary ions produced by the impact of energetic incident ions such as H+, H2+, H3+, Ar+, and He+ on polycrystalline molybdenum foil and single crystal W(110) have been measured. The secondary energy spectra and yield are relatively insensitive to the ion type and energy, but very sensitive to the physical-chemical state of the surface. In particular, the addition of cesium increases the negative ion yield of molybdenum and tungsten by several orders of magnitude as well as shifting the energy distribution to lower energies. The spontaneous emission of H- from W(110) was observed in an ambient of cesium vapor and hydrogen at temperatures above 600 K. The mechanism in this case appears to be surface chemi-ionization. The energy spectrum for this process is similar to that resulting from ion impact at low energies, but the surface chemi-ionization spectrum lacks the higher energy tail (E is less than 10 eV) characteristic of secondary ion emission.

Descriptors :   *Particle collisions, *Secondary emission, *Mass spectrometry, Tungsten, Molybdenum, Cesium, Anions, Surface reactions, Energy levels, Ionization, Hydrogen, Mass spectrometers

Subject Categories : Atomic and Molecular Physics and Spectroscopy
      Nuclear Physics & Elementary Particle Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE