Unabridged Resonant Contribution to the X-ray Scattering Length

作者：Lovesey Stephen William^*; Balcar Ewald

来源：Journal of the Physical Society of Japan, 2012, 81(1): 014710.

DOI：10.1143/JPSJ.81.014710

• resonant Bragg diffraction
• dichroic signals
• magneto-electric multipoles
• polar multipoles

Resonance-enhanced Bragg scattering of x-rays and concomitant dichroic signals are valuable tools for investigation of material properties. In this context parity-odd events E1-E2 and E1-M1 merit special attention. Theoretical analysis of the product of matrix-elements defining the scattering length for the resonant photon absorption and emission process leads to sums of electronic multipoles calculated for equilibrium electron states. The unabridged result retains explicit dependence on the labels of the intermediate state and recovers a common unit tensor present in the formulae describing parity-odd events. In order to add physical insight, the various forms of the unit tensor are correlated with magneto-electric and polar multipoles, which benefit from representations using familiar operators. The description of parity-odd events requires the use of appropriate combinations of photonic tensors and electronic multipoles to achieve correct symmetry properties. After discussing some special cases the new formulae are shown to be in agreement with previously published results.

• 出版日期2012-1