Formation and desorption of negative ions from metal surfaces

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7139644

Baker, D H

Investigations of negative ion and electron emission from gas-covered metal surfaces due to impact of low energy (30-300 eV) positive ions and, separately, photons (2-5 eV) are presented. In both cases, the negative ion formation process is thought to occur via electron tunneling from the surface or its substrate to a sputtered or photodesorbed neutral atom or molecule. In particular, absolute total negative ion and electron yields for collisions of positive alkali ions with a gas-covered Mo substrate have been measured. Mass analysis of the sputtered negative ions show that O[sub 2][sup [minus]] is the dominant ion at low impact energies. This coupled with the fact that threshold energies for observing secondary negative ions and electrons are the same suggests that electron production is correlated to the O[sub 2][sup [minus]] production, and specifically that electrons are the result of autodetachment of excited O[sub 2][sup [minus]]. This hypothesis provides an explanation of the mechanism responsible for the emission of electrons at low impact energies. Relative yields for photodesorbed H[sup [minus]] from a barium substrate have been measured as a function of photon wavelength for the range of 245 to 585 nm. A description of the formation of H[sup [minus]] due to photodesorption of BaH on a surface is consistent with the known energetics of the system. An estimate of the absolute yield of photodesorbed H[sup [minus]] per incident photon has been made.

• Research Organization: College of William and Mary, Gloucester Point, VA (United States). School of Marine Science
• OSTI ID: 7139644
• Country of Publication: United States
• Language: English

Related Subjects

664300* -- Atomic & Molecular Physics-- Collision Phenomena-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
ALKALI METAL COMPLEXES
ANIONS
CHARGED PARTICLES
COLLISIONS
COMPLEXES
DESORPTION
ELECTRON EMISSION
EMISSION
HYDROGEN IONS
ION COLLISIONS
ION EMISSION
ION-ION COLLISIONS
IONS
OXYGEN IONS
PHOTON COLLISIONS
PHOTON-ION COLLISIONS
SORPTION