Polarized Dispersion for X-rays Scattered by an Aromatic Bromide.
Second-rank tensors describing how the real and imaginary dispersion terms f' and f'' depend on photon polarization for Br atoms substituted on a benzene ring have been measured at six energies near the Br K absorption edge in diffraction experiments with synchrotron radiation and crystals of homocubanecarboxylic acid p-bromoanilide. Resonance with a sigma antibonding orbital causes f' to change with polarization as much as 4.3 and f''' as much as 7.5. The tensors for two independent Br atoms are equal, uniaxial and aligned with the respective Br-C bond. Absorption spectra show the average effect of two tensors with different orientations. Atomic coordinates from a new refinement of the structure are listed.
Templeton
L K
LK
Templeton
D H
DH