Ag L3-Edge X-ray Absorption Near-Edge Structure of 4d10 (Ag+) Compounds: Origin of the Edge Peak and Its Chemical Relevance

A peak appearing at the L2,3 X-ray absorption edge often provides the number of empty d states of the X-ray absorbing atoms. Ag+ compounds have a d10 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 dn (n < 10) elements.