Low-energy helium scattering from ordered physisorbed layers of polar molecules

Journal Article · Wed Nov 14 23:00:00 EST 1990 · Journal of Physical Chemistry; (USA)

DOI:https://doi.org/10.1021/j100386a007· OSTI ID:6286262

Rowntree, P A; Scoles, G ^[1]; Ruiz-Suarez, J C ^[2]

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1. Princeton Univ., NJ (USA)
2. Univ. of Waterloo, Ontario (Canada)

Atomic beam diffraction is discussed as a useful method for the structural characterization of mono- and multilayers of gases physisorbed on single-crystal surfaces with some emphasis on experimental techniques. The method is applied to the study of physisorbed phases of polar molecules on the (0001) face of single crystal graphite. On bare graphite CH{sub 3}F forms a commensurate {radical}3 {times} {radical}3R30{degree} structure with all the molecular dipoles parallel to each other while CH{sub 3}Cl and CH{sub 3}Br form uniaxially incommensurate phases with two molecules per unit cell that have the dipoles antiparallel to each other. If Xe-covered graphite is used as a substrate, the unit cell of CH{sub 3}F doubles with the two dipoles becoming also antiparallel, while the study of CH{sub 3}Cl and CH{sub 3}Br is complicated by layer mixing phenomena. HCl on graphite forms an incommensurate closed packed structure, rotated by 30{degree} with respect to the substrate lattice, with a lattice parameter of 3.80 {angstrom}. On the same substrate ammonia shows instead ringlike diffraction patterns indicative of a two-dimensional polycrystalline phase in which the crystalline domains have a large degree of azimuthal disorder.

• OSTI ID: 6286262
• Journal Information: Journal of Physical Chemistry; (USA), Journal Name: Journal of Physical Chemistry; (USA) Vol. 94:23; ISSN 0022-3654; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
656003 -- Condensed Matter Physics-- Interactions between Beams & Condensed Matter-- (1987-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ADSORPTION
ATOMIC BEAM DIFFRACTION
BROMINATED ALIPHATIC HYDROCARBONS
CARBON
CHLORINATED ALIPHATIC HYDROCARBONS
COHERENT SCATTERING
DATA
DIFFRACTION
ELEMENTAL MINERALS
ELEMENTS
EXPERIMENTAL DATA
FLUIDS
FLUORINATED ALIPHATIC HYDROCARBONS
GASES
GRAPHITE
HALOGENATED ALIPHATIC HYDROCARBONS
HELIUM
INFORMATION
LATTICE PARAMETERS
METHYL BROMIDE
METHYL CHLORIDE
METHYL FLUORIDE
MINERALS
NONMETALS
NUMERICAL DATA
ORGANIC BROMINE COMPOUNDS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
RARE GASES
SCATTERING
SORPTION
SURFACE PROPERTIES