The effect of water molecule configurations on the type of core ionized site: O1s core ionization of ascorbic acid in water

Abstract

The analysis of photoelectron spectra can be a complex and uncertain process, primarily due to the overlap of the peaks in the spectra. This overlap can lead to inaccuracies in the reported ionization energies derived from the binding energy positions of the visible peaks. This constraint explains the absence or inaccurate reporting of ionization energy values for certain biomolecules in the articles. Reliable theoretical methods are required for the interpretation of experimental results. In the present work, the overlap of photoelectron spectrum peaks is of particular importance, given the similarity between the molecular oxygen signatures of ascorbic acid (AA) and water. We used the SAC-CI method, based on the ONIOM model, to examine how the first coordination shell of water molecules affected the O1s core ionization energy of AA at 298 and 350 K temperatures. Our investigation shows that water’s photoelectron spectrum covers the O1s spectrum of AA.