Inner shell excitation and dissociation of condensed formamide

Carbon and nitrogen K-shell excitation and dissociation of condensed formamide at 96 K were studied by near edge X-ray absorption fine structure (NEXAFS) recorded by total electron yield (TEY), total ion yield (TN) and photon-stimulated desorption (PSD) yield of H+ measurements. It was found that electronic transitions from the C Is or the N Is to the sigma* (C-FI and/or N-H) enhanced ion yields of H+ from the C-H and/or N-H functional groups. This selective dissociation indicates that the corresponding unoccupied molecular orbital has an antibonding character of the C-H and/or N-H. To investigate the molecular orientation of condensed formamide, incidence-angle-dependent TEY-NEXAFS spectra were measured. The CNO plane of the adsorbed formamide molecule is determined to be tilted away from the surface by an averaged angle of about 42 degrees. (C) 2001 Elsevier Science B.V. All rights reserved.