Theoretical investigation of the NEXAFS spectra of acrylonitrile near the carbon and the nitrogen K-edge

The polarization-dependent NEXAFS spectra at the C 1s and the N 1s edges of acrylonitrile, CH₂CHCN, have been investigated theoretically by means of density functional methods. Discrete absorption lines were calculated by using the transition-state approximation within both the LCGTO-DF method and the MS-Xα technique. The continuum part was studied by the recently developed LDKL-DF method and compared to CMS-Xα calculations. The results were found in excellent agreement with experimental data for an acrylonitrile multilayer on a metal substrate, confirming the experimentally derived adsorption geometry and spectral assignments. The analysis of the continuum wave functions and eigenchannels provides additional insight into the photoabsorption and photoionization final states. Moreover, the present calculations suggest that nearly all peaks above the ionization potential are of one-electron character, reflecting the three dominating shape resonances.