Liquid water, 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 ca. 2500 Pa, or higher in some cases. With NAP-XPS, XPS can be used to analyze moderately volatile liquids, biological samples, porous materials, and/or polymeric materials that outgas significantly. In this submission, we show survey, O 1s, O KLL, and valence band NAP-XPS spectra from liquid water, a material that could not be analyzed at moderate pressures by conventional approaches. The O 1s signal was fit to two components attributed to liquid and vapor phase water. The carbon in the survey spectrum is attributed to contaminants in the water and/or adventitious carbon.