title: Communication: On the first ionization threshold of the C2H radical.
abstract: The slow photoelectron spectrum of the ethynyl radical has been recorded for the first time by using the DESIRS beamline of the SOLEIL synchrotron facility. Ethynyl was generated using a microwave discharge flow tube. The observation of the X+Π3←XΣ+2 transition allowed the first direct measurement of the adiabatic ionization threshold of this radical (EI= 11.641(5) eV). The experimental results are supported by ab initio calculations. Our preliminary investigation of the cationic ground state potential energy surfaces predicts a non-negligible Renner-Teller effect which has not been discussed previously.
authors.affiliation: Institut des Sciences Moléculaires d'Orsay (ISMO), CNRS, Univ. Paris-Sud, Université Paris-Saclay, F-91405 Orsay, France.
authors.forename: B
authors.initials: B
authors.lastname: Gans
authors.affiliation: Synchrotron SOLEIL, L'Orme des Merisiers, Saint Aubin BP 48, F-91192 Gif sur Yvette Cedex, France.
authors.forename: G A
authors.initials: GA
authors.lastname: Garcia
authors.affiliation: Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Holzmeier
authors.affiliation: Synchrotron SOLEIL, L'Orme des Merisiers, Saint Aubin BP 48, F-91192 Gif sur Yvette Cedex, France.
authors.forename: J
authors.initials: J
authors.lastname: Krüger
authors.affiliation: Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Röder
authors.affiliation: Laboratoire de Chimie Physique, UMR 8000 CNRS, Univ. Paris-Sud, Univ. Paris-Saclay, Bât. 350, Centre Universitaire Paris-Sud, F-91405 Orsay Cedex, France.
authors.forename: A
authors.initials: A
authors.lastname: Lopes
authors.affiliation: Université Lille, CNRS, UMR 8522-PC2A-Physicochimie des Processus de Combustion et de l'Atmosphère, F-59000 Lille, France.
authors.forename: C
authors.initials: C
authors.lastname: Fittschen
authors.affiliation: Institut des Sciences Moléculaires, UMR 5255 CNRS, Université de Bordeaux, Bât. A12, 351 cours de la Libération, F-33405 Talence Cedex, France.
authors.forename: J-C
authors.initials: JC
authors.lastname: Loison
authors.affiliation: Laboratoire de Chimie Physique, UMR 8000 CNRS, Univ. Paris-Sud, Univ. Paris-Saclay, Bât. 350, Centre Universitaire Paris-Sud, F-91405 Orsay Cedex, France.
authors.forename: C
authors.initials: C
authors.lastname: Alcaraz