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Polarized Dispersion for X-rays Scattered by an Aromatic Bromide
Journal of Synchrotron Radiation
|January 1, 1995
Summary
Bromine (Br) atom polarization effects on photon dispersion were measured using synchrotron diffraction. Resonance with sigma antibonding orbitals significantly alters dispersion terms f' and f''.
Area of Science:
- Solid-state physics
- Crystallography
- Atomic physics
Background:
- Understanding atomic interactions with polarized photons is crucial for materials science.
- Dispersion terms (f' and f'') describe how materials interact with light.
- Bromine K absorption edge provides insights into electronic structure.
Purpose of the Study:
- To measure second-rank tensors describing photon polarization dependence of Br dispersion terms (f' and f'').
- To investigate the influence of resonance with sigma antibonding orbitals on these dispersion terms.
- To determine the orientation and symmetry of these tensors in a benzene ring substitution.
Main Methods:
- Diffraction experiments utilizing synchrotron radiation.
- Crystals of homocubanecarboxylic acid p-bromoanilide were used.
- Measurements were taken at six energies near the Br K absorption edge.
Main Results:
- Second-rank tensors for Br atoms were measured.
- Resonance effects caused significant changes in f' (up to 4.3) and f''' (up to 7.5) with polarization.
- Tensors for independent Br atoms were found to be equal, uniaxial, and aligned with the Br-C bond.
- Absorption spectra revealed the average effect of differently oriented tensors.
Conclusions:
- The study successfully characterized the polarization dependence of Br dispersion terms.
- Resonance with sigma antibonding orbitals plays a key role in modulating these interactions.
- The findings provide detailed structural and electronic information about bromine in organic crystals.
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