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Circular dichroism effects in atomic x-ray scattering

N. L. Manakov*, A. V. Meremianin*, J. P. J. Carney$^{\dag }$ and R. H. Pratt$^{\dag }$

*Department of Physics, Voronezh State University, Voronezh 394693, Russia

$^{\dag }$Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260

15 June, 1999


It is shown that a specific beyond-dipole-approximation polarization effect in elastic photon-atom scattering, resulting in circular dichroism (CD) when the scattered photon has a suitable observed linear polarization, has significance in the x-ray regime. Ground state atoms are considered, assumed to be randomly oriented. The cross section, given our assumptions, is written in terms of photon Stokes parameters and four real photon-polarization-independent atomic parameters (which depend on the vectors of the problem and the two invariant scattering amplitudes). Numerical results are given for the case of scattering from ground-state atoms with Z=29, Z=54 and Z=92. Attention is given to determining the regime where the dichroism effect may be experimentally observable. It is seen to be largest for intermediate angles, high Z and high (hundreds of keV) photon energies, increasing to an approximately 20% effect in cross sections. The parameter determining this effect is also responsible for the appearance of elliptically polarized scattered photons for the case of a suitable linearly polarized incident beam.


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Eoin Carney