Effects of bonding on the energy distribution of electrons scattered elastically at high momentum transfer
- Atomic and Molecular Physics Laboratories6, Research School of Physical Sciences and Engineering, Australian National University, Canberra ACT 0200 (Australia)
High-resolution measurements of 40-keV electrons scattered over 44.3 deg. from evaporated carbon films are presented. The observed width of the energy distribution of electrons scattered from carbon is significantly larger than the experimental energy resolution, and its position is shifted to lower energy. Measurements were done for transmission and reflection geometries for thin films with thicknesses varying from 90 A ring to 1400 A ring . The observed peak shape is largely independent of the thickness and measurement geometry. The peak shape deviates from Gaussian in all cases, in a way consistent with theories that describe these processes beyond the impulse approximation. The energy shift of the carbon peak is measured by evaporating a small amount of Au on these films. Separation of the Au and C peak is somewhat smaller than calculated assuming scattering from free C and Au atoms, but independent of measurement geometry. Finally spectra were measured from highly oriented pyrolytic graphite (HOPG) films. Now different widths are observed in reflection geometry and transmission geometry. This is attributed to the anisotropy of the motion of the C atoms in HOPG. Also the Au-C separation is slightly orientation dependent for HOPG. All observations agree at least semiquantitatively with neutron Compton scattering results, a related scattering experiment that studies neutron-atom collisions at similar momentum transfers.
- OSTI ID:
- 20853892
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 74, Issue 20; Other Information: DOI: 10.1103/PhysRevB.74.205407; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANISOTROPY
ATOM COLLISIONS
ATOMS
CHEMICAL BONDS
COMPTON EFFECT
ELECTRON COLLISIONS
ELECTRONS
ENERGY RESOLUTION
ENERGY SPECTRA
GEOMETRY
GOLD
GRAPHITE
IMPULSE APPROXIMATION
KEV RANGE
MOMENTUM TRANSFER
NEUTRONS
ORIENTATION
REFLECTION
SURFACES
THIN FILMS