Primary ion dependence of LiF direct recoil intensities and ion fractions

Journal Article · Sun Feb 15 04:00:00 EST 1987 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.452755· OSTI ID:6925732

Chen, J N; Shi, M; Rabalais, J W

Time-of-flight (TOF) spectra of the scattered and recoiled particles resulting from 1--10 keV He/sup +/, Ne/sup +/, Ar/sup +/, Kr/sup +/, and Xe/sup +/ ions impingent on surfaces of LiF thin films have been obtained. Measurements of directly recoiled (DR) neutrals plus ions and neutrals alone are used to calculate positive and negative ion fractions Y/sub +,-/ from DR events. The oppositely charged ion fractions have a distinctly different behavior as a function of kinetic energy. The Y/sub +/ values exhibit a threshold at low energy followed by a plateau region at higher energy while the Y/sub -/ values are maximum in the low energy region followed by a decreasing yield as energy increases. The energy dependence of Y/sub +,-/ is interpreted in terms of the recently developed model (J. Chem. Phys. 85, 3615 (1986)) for electronic charge exchange in keV ion/surface collisions which considers electron promotions in the close atomic encounter and resonant and Auger transitions along the outgoing trajectory. The ionization potential of the primary ion relative to the energy levels of the target atom is shown to have a large influence on charge exchange in the close encounter. The ratio of direct recoil to scattering particle flux increases by a factor of >10/sup 2/ from He to Xe; scattering and recoil cross sections are used to model this process.

• Research Organization: Department of Chemistry, University of Houston, Houston, Texas 77004
• OSTI ID: 6925732
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 86:4; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640301* -- Atomic
Molecular & Chemical Physics-- Beams & their Reactions
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALKALI METAL COMPOUNDS
ARGON IONS
BEAMS
CHARGED PARTICLES
COLLISIONS
ENERGY RANGE
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
HELIUM IONS
ION BEAMS
ION COLLISIONS
IONS
KEV RANGE
KEV RANGE 01-10
KRYPTON IONS
LITHIUM COMPOUNDS
LITHIUM FLUORIDES
LITHIUM HALIDES
NEON IONS
RECOILS
SURFACES
TIME-OF-FLIGHT METHOD
XENON IONS