Ionization of large homogeneous and heterogeneous clusters generated in acetylene-Ar expansions: Cluster ion polymerization
Abstract
Pure acetylene and mixed Ar-acetylene clusters are formed in supersonic expansions of acetylene/argon mixtures and analysed using reflectron time-of-flight mass spectrometer with variable electron energy ionization source. Acetylene clusters composed of more than a hundred acetylene molecules are generated at the acetylene concentration of approximate to 8%, while mixed species are produced at low concentrations (approximate to 0.7%).
The electron energy dependence of the mass spectra revealed the ionization process mechanisms in clusters. The ionization above the threshold for acetylene molecule of 11.5 eV results in the main ionic fragment progression (C2H2)(n)(+).
At the electron energies >= 21.5 eV above the CH+CH+ dissociative ionization limit of acetylene the fragment ions nominally labelled as (C2H2)(n)CH+, n >= 2, are observed. For n = 2(C2H2)(m >= 2)(+) at approximate to 13.7 eV is discussed in terms of an exciton transfer mechanism. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4796262]