Carbon dioxide gas, CO₂(g), by near-ambient pressure XPS

Near-ambient pressure x-ray photoelectron spectroscopy (NAP-XPS) is a less traditional form of XPS that allows samples to be analyzed at relatively high pressures, i.e., at greater than 2500 Pa. With NAP-XPS, XPS can probe moderately volatile liquids, biological samples, porous materials, and/or polymeric materials that outgas significantly. In this submission, we show the survey, O 1s, C 1s, valence band, O KLL Auger, and C KLL Auger NAP-XPS spectra of gaseous carbon dioxide, CO₂, a material that would be difficult to analyze by conventional XPS. A small N 1s signal from N₂(g) is also observed in the survey spectrum. The C 1s and O 1s signals in the narrow scans are fit to Gaussian–Lorentzian sum and asymmetric Lorentzian (LA) functions. Better fits are obtained with the LA synthetic line shape. Since it is likely that CO₂(g) will be present in other NAP-XPS analyses, these data should serve as a useful reference for other researchers.