Experimental and theoretical study of intense shake-up structures in the XPS spectra of nitrobenzenes and nitrosobenzenes

Abstract

The N 1s and O 1s energy regions of the XPS spectra of para-substituted nitrobenzenes and nitrobenzenes [ p-X-C 6H 4-NO 2: X = H, OH, OCH 3, NH 2 and N(CH 3) 2; p-X-C 6H 4-NO: X = H, Cl, OCH 3 and N(CH 3) 2] present, close to the main lines, one (NO 2-derivatives) or two (NO-derivatives) shake-up peaks whose intensity increases steadily with the electron-releasing ability of the substituent. All main energy and intensity trends experimentally observed are correctly reproduced by CNDO/S-Cl calculations, both within given compounds and along the two series. The origin of the satellites and the differences noted between the two series are discussed. The present experimental and theoretical results are in complete agreement with our qualitative explanation of the multi-peak structures previously observed in nitroanilines and other polar aromatic nitro-derivatives.