Water vapor electron scattering cross-section measurements using a hydrophobic ionic liquid

The interface of ionic liquid (IL) 1-ethyl-3-methylimidazolium-bis-(trifluoromethylsulfonyl)-imide, [EMIM][Tf2N], was examined in the presence of water vapor using lab-based ambient pressure X-ray photoelectron spectroscopy (APXPS) with a monochromatic Al K alpha X-ray source. Room temperature water vapor exposures to [EMIM][Tf2N] ranged from 10(-6) to 2.0 Torr with no evidence of water uptake at the IL-vapor interface. The hydrophobic nature of [EMIM][Tf2N] allowed for measuring the attenuation of F 1s, O 1s, N 1s, C 1 s and S 2p APXPS peaks as a function of pressure, allowing for the determination of the electron scattering cross-section (sigma(e)) of gas phase water. The elemental diversity of [EMIM][Tf2N] allowed for the extraction of a., over a 520 eV kinetic energy range in the absence of a variable energy X-ray source. Herein we show that lab-based APXPS in combination with an elementally diverse, unreactive substrate is an effective tool for the determination of electron scattering cross sections for gas phase species. (C) 2017 Elsevier B.V. All rights reserved.