Seminars Archive

State-selected ion-molecule reactions studied with synchrotron radiation in LURE

Abstract
The study of reaction cross sections as a function of both internal and collision energy is essential to understand their mechanisms. Our experimental set-up allows both by combining two techniques. Reactant ions are formed by photoionisation in valence shells with synchrotron radiation in the vacuum ultraviolet range (8 to 40 eV). They are then selected in continuously variable internal energy with a coincidence technique between threshold photoelectrons and photoions. The collision energy can be varied from nearly thermal energy to 20 eV in the laboratory frame by a radiofrequency octopole ion guide technique. Another experimental set-up equipped with a supersonic molecular beam crossing the monochomatized synchrotron VUV radiation allows us to study unimolecular reactions. It is another way of probing the reacting potential energy hypersurface by photoionizing Van der Waals molecules formed with the two neutral reactants and comparing the fragments with the bimolecular reaction products. Ion molecule reactions between small hydrocarbon molecules (acetylene, methane, ethane) will be presented, as well as intracluster reactions in mixed acetylene-ethane molecular clusters.