title: Ionization photophysics and spectroscopy of cyanoacetylene.
abstract: Photoionization of cyanoacetylene was studied using synchrotron radiation over the non-dissociative ionization excitation range 11-15.6 eV, with photoelectron-photoion coincidence techniques. The absolute ionization cross-section and spectroscopic aspects of the parent ion were recorded. The adiabatic ionization energy of cyanoacetylene was measured as 11.573 ± 0.010 eV. A detailed analysis of photoelectron spectra of HC3N involves new aspects and new assignments of the vibrational components to excitation of the A(2)Σ(+) and B(2)Π states of the cation. Some of the structured autoionization features observed in the 11.94 to 15.5 eV region of the total ion yield (TIY) spectrum were assigned to two Rydberg series converging to the B(2)Π state of HC3N(+). A number of the measured TIY features are suggested to be vibrational components of Rydberg series converging to the C(2)Σ(+) state of HC3N(+) at ≈17.6 eV and others to valence shell transitions of cyanoacetylene in the 11.6-15 eV region. The results of quantum chemical calculations of the cation electronic state geometries, vibrational frequencies and energies, as well as of the C-H dissociation potential energy profiles of the ground and electronic excited states of the ion, are compared with experimental observations. Ionization quantum yields are evaluated and discussed and the problem of adequate calibration of photoionization cross-sections is raised.
authors.affiliation: LERMA UMR CNRS 8112, Observatoire de Paris-Meudon, 5 place Jules-Jansen, 92195 Meudon, France.
authors.forename: Sydney
authors.initials: S
authors.lastname: Leach
authors.affiliation: Synchrotron SOLEIL, L'Orme des Merisiers, St. Aubin, B.P. 48, 91192, Gif-sur-Yvette Cedex, France.
authors.forename: Gustavo A
authors.initials: GA
authors.lastname: Garcia
authors.affiliation: LISA UMR CNRS 7583, Université Paris Est Créteil and Université Paris Diderot, Institut Pierre Simon Laplace, 61 Avenue du Général de Gaulle, 94010 Créteil, France.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Mahjoub
authors.affiliation: LISA UMR CNRS 7583, Université Paris Est Créteil and Université Paris Diderot, Institut Pierre Simon Laplace, 61 Avenue du Général de Gaulle, 94010 Créteil, France.
authors.forename: Yves
authors.initials: Y
authors.lastname: Bénilan
authors.affiliation: Synchrotron SOLEIL, L'Orme des Merisiers, St. Aubin, B.P. 48, 91192, Gif-sur-Yvette Cedex, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Fray
authors.affiliation: LISA UMR CNRS 7583, Université Paris Est Créteil and Université Paris Diderot, Institut Pierre Simon Laplace, 61 Avenue du Général de Gaulle, 94010 Créteil, France.
authors.forename: Marie-Claire
authors.initials: MC
authors.lastname: Gazeau
authors.affiliation: Synchrotron SOLEIL, L'Orme des Merisiers, St. Aubin, B.P. 48, 91192, Gif-sur-Yvette Cedex, France.
authors.forename: François
authors.initials: F
authors.lastname: Gaie-Levrel
authors.affiliation: LERMA UMR CNRS 8112, Observatoire de Paris-Meudon, 5 place Jules-Jansen, 92195 Meudon, France.
authors.forename: Norbert
authors.initials: N
authors.lastname: Champion
authors.affiliation: LISA UMR CNRS 7583, Université Paris Est Créteil and Université Paris Diderot, Institut Pierre Simon Laplace, 61 Avenue du Général de Gaulle, 94010 Créteil, France.
authors.forename: Martin
authors.initials: M
authors.lastname: Schwell
mesh_terms: D000114:Acetylene / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D004583:Electrons; D004735:Energy Transfer; D007477:Ions / Q000737:chemistry; D009570:Nitriles / Q000737:chemistry / Q000378:metabolism*; D055585:Physical Phenomena; D011789:Quantum Theory; D017356:Synchrotrons
chemical_list: D007477:Ions; D009570:Nitriles; C513097:cyanoacetylene; D000114:Acetylene