title: Threshold photoelectron spectroscopy of unstable N-containing compounds: Resolution of ΔK subbands in HNCO(+) and vibrational resolution in NCO(.).
abstract: The threshold photoelectron spectra (TPES) of two unstable nitrogen-containing species, HNCO and NCO, were recorded utilizing vacuum ultraviolet synchrotron radiation. Both are intermediates in combustion processes and play a role in the removal of nitrogen oxides from exhaust gases. The rovibronic structure of the first band in the TPES of HNCO(+) was analyzed within the framework of an orbital ionization model, and the resolved structure of the origin band was assigned to ΔK subbands. An ionization energy of 11.602 ± 0.005 eV was determined and the vibrational structure of the cationic ground state was analyzed by a Franck-Condon fit. Low lying electronically excited states of HNCO(+) were also observed. In a second series of experiments, the NCO radical was generated by flash pyrolysis from chlorine isocyanate. The ionization energy to the X(+) (3)Σ(-) ground state was determined to be 11.76 ± 0.02 eV, while for the a(+) (1)Δ state, a value of 12.93 ± 0.02 eV was obtained. Vibrational structure was observed for both states, and bands were assigned by Franck-Condon simulations.
authors.affiliation: Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Holzmeier
authors.affiliation: Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Lang
authors.affiliation: Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany.
authors.forename: Ingo
authors.initials: I
authors.lastname: Fischer
authors.affiliation: Synchrotron SOLEIL, l'Orme des Merisiers, Saint Aubin BP 48, F-91192 Gif sur Yvette Cedex, France.
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Tang
authors.affiliation: Laboratoire de Chimie-Physique, UMR 8000 CNRS and Université Paris-Sud 11, F-91405 Orsay Cedex, France.
authors.forename: Barbara
authors.initials: B
authors.lastname: Cunha de Miranda
authors.affiliation: Laboratoire de Chimie-Physique, UMR 8000 CNRS and Université Paris-Sud 11, F-91405 Orsay Cedex, France.
authors.forename: Claire
authors.initials: C
authors.lastname: Romanzin
authors.affiliation: Laboratoire de Chimie-Physique, UMR 8000 CNRS and Université Paris-Sud 11, F-91405 Orsay Cedex, France.
authors.forename: Christian
authors.initials: C
authors.lastname: Alcaraz
authors.affiliation: Molecular Dynamics Group, Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Hemberger