Core excitation and de-excitation spectroscopies of free atoms and molecules

This article provides a review of the current status of core excitation and de-excitation spectroscopy studies of free atoms and molecules using a high-resolution soft X-ray monochromator and a high-resolution electron energy analyzer, installed in the soft X-ray photochemistry beam line at SPring-8. Experimental results are discussed for 1s excitation of Ne, O 1s excitation of CO and H₂O, and F 1s excitation of CF₄.