X-Ray Natural Circular Dichroism

We report the first observation of natural circular dichroism (CD) in the x-ray region. Measurements at the Nd $L_3$ edge in single crystals of ${\mathrm{Na}}_3\mathrm{Nd}(\mathrm{digly}{)}_3̇2{\mathrm{NaBF}}_4̇6{\mathrm{H}}_2\mathrm{O}$ show CD with a dissymmetry factor $g\approx {10}^{-3\mathrm{}}$ of the same order of magnitude as observed in the visible-uv region and $\sim 100$ times greater than in the vibrational infrared. Calculations using multiple scattering theory (MST) are in excellent agreement with the measured CD in the near-edge region (about 100 eV from the rising edge) and show that the effect arises from the electric dipole-electric quadrupole interference mechanism.