SUM-RULES FOR X-RAY-ABSORPTION AND DICHROISM

The derivation of sum rules for X-ray absorption dichroism from a sing le ion is reviewed. A possible extension of the formalism to cover the important case of itinerant electrons is also mentioned. In my lectur e at the Thee Thole Memorial Conference, I drafted a brief history of the sum rules for X-ray absorption and dichroism, drawing from my reco llections and notebooks. A detailed account of the material, reorganis ed and partly expanded, is given in the current paper. (C) 1997 Elsevi er Science B.V.