Untersuchung der Ionenchemie von Perfluoralkylphosphor- und Siliziumverbindungen - Entwicklung eines Miniaturionenkäfigs für die ICR-Spektrometrie

Abstract

In the first part of this thesis the gas phase ion chemistry of perfluoroalkylated phosphanes and alkylsilanes has been examined.The phosphanes form phosphonium ions as products of ion/molecule reactions. In the negative mode hypervalent phosphoranides with two fluorine or chlorine ligands at phosphorus could be detected.The alkylsilanes yielded silyl cations R3Si (R = CH3 or F) as major fragment ions. Clustering of fragment ions with neutrals produced fluoronium ions [((CH3)3Si)2F] . In addition, hypervalent siliconates [(RF)2Si(CH3)3]- were generated through dissociative electron attachment to RFSi(CH3)3 and in ion/molecule reactions with SF5- and SF6-.The results from the mass spectra were supported by DFT calculations. In the second part the performance of miniaturized ICR cells with 2 and 4 mm radius has been examined. In the smallest cell with r = 2 mm the measured cyclotron frequencies show strong deviations from values calculated by the methods applicable to cells of larger size. The quadrupolar approximation for the trapping potential is no longer applicable.Due to the decreased cell volume space-charge effects have a larger effect than in normal cells.The results from the 4 mm cells were comparable to those from larger cells with r = 21 mm. Furthermore, ICR cells of 4mm radius were employed with added screening electrodes in order to minimize the effects of the trapping potential. Potentials and ion trajectories were simulated with SIMION.