excitation level

in X-ray spectroscopy
https://doi.org/10.1351/goldbook.E02252
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.
Source:
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 [Terms] [Paper]