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Molecular Physics seminar

Chemistry of molecular ions in laboratory plasmas and planetary atmospheres

by Dr Daniela Ascenzi (University of Trento, Italy)

FA32 ()


An overview of the most recent research from our laboratory on the reactivity of molecular ions will be presented, with particular reference to the fields of laboratory plasma systems and planetary ionospheres: Atmospheric pressure non-thermal plasmas present several attractive technological applications ranging from remediation of toxic gases to deposition of nanostructured materials, hydrocarbon reforming and enhanced ion sources for mass spectrometric applications. We study the chemistry inside such type of plasmas by on-line and off–line detection of ionic and neutral products. To elucidate the chemical mechanisms in operation we couple targeted experiments using isotopically labelled reagents and ion-molecule reactions in a guided ion beam mass spectrometer with ab initio calculations. A great research effort is focussed on the modelling of the hydrocarbon atmosphere of Titan, the second largest moon in the Solar system. Heavy ions with masses over 100 amu have been detected in significant amounts in Titan’s ionosphere, with possible chemical structures including PAHs, nitrile aromatic polymers, fullerenes and polyphenyls. In spite of several laboratory investigations, new experimental data are still required to provide a quantitative comparison between the in situ observations and the proposed models. To shed light on the growth mechanisms of aromatic hydrocarbons initiated by charged particles, we have studied the reaction of ethyl, phenyl and naphthyl cations with benzene. Finally,a brief account on the topic of reactivity of molecular dications will be given, with reference to the potential applications of doubly charged cations as superelectrophilic reagents for the activation of noble gases and the synthesis of new rare gas compounds.