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 ®ne structure (NEXAFS) recorded by total electron yield (TEY), total ion yield (TIY) and photon-stimulated desorption (PSD) yield of H‡ measurements. It was found that electronic transitions from the C 1s or the N 1s to the s (C±H 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 428. # 2001 Elsevier Science B.V. All rights reserved