X-Ray Photoelectron Spectroscopy as a Probe of Beam-Induced Surface Decomposition of 1-Octyl-3-Methylimidazolium Tribromide

Abstract

A systematic investigation of the beam-induced surface decomposition of a typical trihalide ionic liquid, 1-octyl-3-methylimidazolium tribromide, was conducted by X-ray photoelectron spectroscopy, and the electronic environment of the bromine region is discussed. The newly formed component was assigned to bromide, based on the measured Br 3d binding energy. The atomic loss of bromine as a function of exposure time under the X-ray beam is analyzed in detail. The analysis suggests that 1-octyl-3-methylimidazolium tribromide is decomposed under X-ray beam irradiation to yield 1-octyl-3-methylimidazolium bromide and liquid bromine, the latter of which subsequently leaves the system under the ultrahigh vacuum conditions.