Experimental Studies of Secondary Ion Emission from Well-Characterized Surfaces.
IRT CORP SAN DIEGO CA
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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 HD 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 W110 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 W110 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.
- Atomic and Molecular Physics and Spectroscopy
- Nuclear Physics and Elementary Particle Physics