Darmstadt 2008 – wissenschaftliches Programm
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MS: Fachverband Massenspektrometrie
MS 2: Ionenfallen- und FT-IZR-MS, Moleküle, Cluster, Zerfälle und Reaktionen
MS 2.7: Vortrag
Montag, 10. März 2008, 18:15–18:30, 3E
Photoionization and Fragmentation of Closo-Carboranes — •Norman Frank Riehs1, Hans-Werner Jochims1, Ertugrul Serdaroglu1, Peter A. Dowben2, and Eckart Rühl1 — 1Physikalische und Theoretische Chemie, Freie Universität Berlin, Takustr. 3, 14195 Berlin — 2Department of Physics and Astronomy, University of Nebraska-Lincoln, NE 68588-0111, U.S.A.
Photoionization and photon-induced fragmentation of isomeric icosahedral closo-carboranes by monochromatic synchrotron radiation is reported. Vacuum ultraviolet radiation from the 3 m NIM-I beam line at the storage ring BESSY (Berlin) was used for the experiments. This allows us to measure ionization thresholds and fragmentation patterns at various photon energies. In spite of complexities that result because of the natural isotope abundance of boron and photon-induced loss of hydrogen, the distinct mass spectrometry fragmentation patterns have been partially identified. At low photoionization energies, we find that the loss of atomic hydrogen corresponds to even numbers of hydrogen atoms. Distinct differences between the isomers of closo-dicarbadodecaborane (orthocarborane (1,2-C2B10H12), metacarborane (1,7-C2B10H12), paracarborane (1,12-C2B10H12) are observed indicating that the loss of pairs of hydrogen depends on the carbon placement within the carborane cage. Furthermore, fragmentation of the cage into singly charged fragments of variable mass is observed along with stable doubly charged intact carborane cages. These results are discussed along with plausible fragmentation mechanisms.