excitation level

in X-ray spectroscopy
X-ray levels have various degrees of ionization -- single, double or higher -- and may in some cases also be electrically neutral. An excitation level (exciton) is an electrically neutral X-ray level with an expelled electron bound in the field of a core electron vacancy.
PAC, 1991, 63, 735. 'Nomenclature, symbols, units and their usage in spectrochemical analysis - VIII. Nomenclature system for X-ray spectroscopy (Recommendations 1991)' on page 738 (https://doi.org/10.1351/pac199163050735)