Non-reciprocal X-ray linear dichroism.

Recently, a new optical effect was observed by Goulon, Rogalev, Goulon-Ginet, Benayoun, Paolasini, Brouder, Malgrange & Metcalf [Phys. Rev. Lett. (2000), 85, 4385-4388] using linearly polarized synchrotron radiation. The authors have correctly analysed the effect using the mathematical framework of Buckingham and Barron. A brief review is given with the underlying simplicity discussed from a symmetry point of view.