Observation of selective desorption of one-phonon inelastically scattered He atoms from a LiF crystal surface

Journal Article · Sat Aug 15 04:00:00 EDT 1981 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.442257· OSTI ID:6315641

Brusdeylins, G; Doak, R B; Toennies, J P

Measurements of angular distributions for scattering of low energy (roughly-equal20 meV) monoenergetic (..delta..v/v = 0.8% FWHM) He beams from a LiF (001) crystal along the <100> and <110> directions and from a NaF (001) crystal along the <100> direction reveal a large number of mostly small maxima and minima between the specular and diffraction peaks. Typical intensities of these features are about 10/sup -3/ of the specular peak. Time-of-flight spectra of the scattered atoms at the incident angles corresponding to the maxima reveal that the atoms were inelastically scattered by single phonons. From the known bound state energies for both systems He--LiF and He--NaF, we find that most of the maxima can be explained by a two step process in which the atoms are first elastically selectively adsorbed by diffraction into an in-plane bound state and then are subsequently desorbed as a result of a single phonon inelastic process. From the observed half-widths the lifetimes of atoms in the trapped states are found to depend on the vibrational quantum number and for the weakest bound state is as large as 60 x 10/sup -12/ sec. Evidence for minima involving selective adsorption into out-of-plane states is also presented.

• Research Organization: Max-Planck-Institut fuer Stroemungsforschung, Boettingerstr. 4-8, D-3400 Goettingen, Federal Republic of Germany
• OSTI ID: 6315641
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 75:4; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640301* -- Atomic
Molecular &amp; Chemical Physics-- Beams &amp; their Reactions
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALKALI METAL COMPOUNDS
ANGULAR DISTRIBUTION
ATOM COLLISIONS
ATOMIC BEAMS
BEAMS
COLLISIONS
DATA
DESORPTION
DISTRIBUTION
ELEMENTS
ENERGY RANGE
EV RANGE
EXPERIMENTAL DATA
FLUIDS
FLUORIDES
FLUORINE COMPOUNDS
GASES
HALIDES
HALOGEN COMPOUNDS
HELIUM
INELASTIC SCATTERING
INFORMATION
LITHIUM COMPOUNDS
LITHIUM FLUORIDES
LITHIUM HALIDES
MILLI EV RANGE
NONMETALS
NUMERICAL DATA
PHONONS
QUASI PARTICLES
RARE GASES
SCATTERING
SORPTIVE PROPERTIES
SURFACE PROPERTIES