X-Ray Detected Optical Activity

摘要

The detection of optical activity (OA) with X-rays became possible with third generation synchrotron radiation sources. X-ray detected OA stems mainly from electric dipole—electric quadrupole interference terms, which mix multipoles of opposite parity: this implies that these effects can be observed only in sys-tems with broken inversion symmetry. Natural OA refers to effects that are even with respect to time-reversal symmetry, while nonreciprocal OA is concerned with time-reversal odd contributions. Various types of X-ray dichroisms related to either natural or nonreciprocal OA were measured at the ESRF and are briefly reviewed in this chapter.