Electronic Structures of Chlorophyll <i>a</i> Investigated by Nitrogen K-Edge X-ray Absorption Spectroscopy under a Radiation-Induced Effect

The electronic structures of high-purity solid chlorophyll <i>a</i> were investigated using nitrogen K-edge X-ray absorption spectroscopy. The C═N π* peaks of the chlorins exhibited characteristic split profiles, which changed progressively with successive scans owing to radiation-induced effects. Inner-shell quantum chemical calculations for structural models of chlorophyll <i>a</i> with different phytol chain lengths assigned the electronic structures of the C═N π* peaks and confirmed that the intensity changes of the C═N π* peaks are caused by cleaving the phytol chain. The influence of the vibration of the phytol chain to the C═N π* peaks of the chlorins was also discussed.