Ag L(3)-edge X-ray absorption near-edge structure of 4d(10) (Ag(+)) compounds: origin of the edge peak and its chemical relevance.

A peak appearing at the L(2,3) X-ray absorption edge often provides the number of empty d states of the X-ray absorbing atoms. Ag(+) compounds have a d(10) state (no d empty states) but show a small peak at the edge. In this research, we systematically studied the edge peak of Ag(+) compounds to understand its origin on the basis of the molecular orbital picture and to obtain a relation of the edge peak intensity to chemical and physical quantities. The edge peak can be formally assigned to the transition from 2p to 5s enhanced by the s-d hybridization. The peak intensity has a negative correlation with a coordination charge but has a positive correlation with the strength of the covalent bond, which is in the reverse order to the other d(n) (n < 10) elements.