INNER-SHELL EXCITATION SPECTROSCOPY OF ANILINE, NITROBENZENE, AND NITROANILINES

Oscillator strengths for C 1s, N 1s, and O 1s excitation spectra of an iline, nitrobenzene, and the isomeric nitroanilines have been derived from inner-shell electron energy loss spectroscopy recorded under low momentum transfer conditions (>2.5 keV impact energy and small scatter ing angle, theta less than or equal to 2 degrees). Extended Huckel Mol ecular Orbital (EHMO) calculations carried out within the equivalent c ore analogy are used to aid spectral interpretation. These spectra are used to investigate the sensitivity of core excitation spectroscopy t o charge transfer interactions in aromatic molecules that have both el ectron-donating and electron-withdrawing substituents. Strong multiele ctron excitation features were not found, although these had been anti cipated from photoemission studies. The C 1s --> pi and N 1s (NH2) -- > pi spectral features of the nitroanilines are found to be strongly dependent on the substitution pattern (ortho, meta, or para).