Experimental and theoretical investigation of the Auger electron spectra of isothiocyanic acid, HNCS

Abstract

We investigate isothiocyanic acid, HNCS, by resonant and nonresonant Auger electron spectroscopy at the K-edge of carbon and nitrogen, and the L_2,3-edge of sulfur, employing soft X-ray synchrotron radiation. The C1s and N1s ionization energies as well as the S2s and S2p ionization energies are determined and X-ray absorption spectra reveal the transitions from the core to the virtual orbitals. Final states for all normal Auger electron spectra and the resonant ones recorded at the carbon and nitrogen edge are assigned and rationalized with theoretical spectra obtained with a wave-function based protocol. The latter is based on ab initio configuration–interaction representations of the bound part of the electronic wave functions, the one-center approximation for Auger intensities, and a moment theory for band shapes. The computed spectra are in very good agreement with the experimental data and most of the relevant signals are assigned. The double ionization energy is derived from the S2p_1/2 spectrum and in good agreement with a recently determined value. The Auger electron spectra are compared with those of the congener HNCO. A similar shape of the normal Auger electron spectra was found for the low binding energy final states, while intensities differed. Similarities are less pronounced in the resonant Auger electron spectra.