Electron- and photon-stimulated desorption of excited hydrogen atoms from alkali halide surfaces

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:5536146

Hudson, L T

This dissertation presents the first extensive investigation of electronically-stimulated desorption of excited hydrogen atoms from alkali halide surfaces. Such desorption is observed in fluorescence spectra from alkali halide compounds which are irradiated by electrons or photons in the presence of H{sub 2}. The fundamental adsorbate-surface interactions which lead to the emission of excited hydrogen atoms has long been an open question. This treatise addresses the nature of this surface bond, its bonding site, and the bond-breaking processes involved in the desorption of excited hydrogen atoms from these surfaces. To this end, the desorption yields of excited hydrogen atoms from the surfaces of KCl, KBr, NaCl, NaF and LiF have been measured as a function of incident photon and electron energy and flux, time of irradiation, dosing pressure of H{sub 2} and sample temperature. Under electron or photon bombardment, halogen atoms are preferentially desorbed leaving a metal-rich surface. The results of this study indicate that the desorption yields of H{sup *} follow the time evolution of this excess metal and its subsequent evaporation as the substrate is heated. Energy dependent yields of H{sup *} exhibit a prominent resonance at threshold when irradiated by photons. This is the first observation of a selective bondbreaking process leading to desorption of neutral hydrogen atoms from a surface. Resonant yields stimulated from compounds which contain the same alkali metal occur energetically at the same incident photon energies. The energy thresholds of electron bombardment studies are also correlated to the alkali component of the substrate.

• Research Organization: Vanderbilt Univ., Nashville, TN (United States)
• OSTI ID: 5536146
• Country of Publication: United States
• Language: English

Related Subjects

656003* -- Condensed Matter Physics-- Interactions between Beams & Condensed Matter-- (1987-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALI METAL COMPOUNDS
BROMIDES
BROMINE COMPOUNDS
CHEMICAL BONDS
CHEMICAL REACTIONS
CHEMISORPTION
CHLORIDES
CHLORINE COMPOUNDS
DESORPTION
ELEMENTS
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
HYDROGEN
IRRADIATION
LITHIUM COMPOUNDS
LITHIUM FLUORIDES
LITHIUM HALIDES
NONMETALS
POTASSIUM BROMIDES
POTASSIUM CHLORIDES
POTASSIUM COMPOUNDS
RADIATION EFFECTS
SEPARATION PROCESSES
SODIUM CHLORIDES
SODIUM COMPOUNDS
SODIUM FLUORIDES
SORPTION
SURFACES