Valence band x‐ray photoelectron spectroscopic studies of carbonate, bicarbonate and formate interpreted by Xα calculations

The valence band and core‐level x‐ray photoelectron spectroscopy (XPS) of carbonate, bicarbonate and formate is reported. There is little difference between these ions in the core XPS spectra. The valence band spectra of carbonate and formate are similar (with some differences in relative intensities) and agree well with the spectrum calculated by multiple‐scattered‐wave Xα calculations. The valence band spectra of carbonate and bicarbonate are found to be identical at ambient temperature, despite the fact that the valence band spectra calculated by Xα calculations are predicted to be different. The carbonate valence band spectrum agrees well with the calculated spectra. When the bicarbonate data are recorded at liquid nitrogen temperature, however, the valence band region agrees well with the calculated spectra. These results indicate that bicarbonate is readily decomposed at ambient temperatures in normal XPS instruments, and that carbonate and bicarbonate can be distinguished by differences in the valence band region if the latter is prevented from decomposition by recording the data at low temperatures.