Radiation damage from EELS and NEXAFS in diesel soot and diesel soot extracts

Carbon NEXAFS and EELS spectra of soot, and NEXAFS spectra of soot extracts, are presented. The EELS spectra of solid soot particles from a TEM-EELS show fewer structures than the corresponding NEXAFS spectra obtained at two different synchrotron beamlines. We attribute radiation damage in the TEM-EELS to the failure at resolving structures of surface functional carbon groups in or on soot. NEXAFS spectra of soot extracts studied with a scanning transmission X-ray microscope show alterations during X-ray exposure, which can be explained by a simple chemical model where oxygen apparently reacts with the sample. When the same extract is studied in an ultrahigh-vacuum beamline, no such alterations are observed.