Mass-resolved ion yield measurements

The time resolved measurement of the different arrival times of the ions yields the masses m. 

Division of Equation [3] by the measured mass-resolved molecular ion current 7 at an anode potential Vq, i.e. in the normal FI spectrum, yields the so-called normalized rate k(r) ... 

We designed a novel three-compartment source (wide-range radiolysis source) for our research mass spectrometer, which was first used to study the radiolysis of methane. The present technique, employing flow, low pressure, localized ionization, and electric fields appears to be a straightforward approach to the problem, and we hoped that this technique would resolve some of the above discrepancies. Our objectives were to (a) determine the percent abundance of the various reactive primary species—ionic and neutral (b) ascertain the percent abundance of stable products under conditions that would minimize subsequent reactions of reactive stable products (c) calculate G values for these products (d) measure the relative contribution of ion-molecule reactions to the formation of stable products (e) obtain the threshold energies and yield curves for such products to assign their precursors and (f) postulate, from the above information and pressure studies, a mechanism for the production of the radiolytic products from methane. 

How far carbocation chemistry has evolved from the old solvolysis days is demonstrated by two recent stmcture determinations the IR spectrum of the nonclassical CHs cation has been measured by solvating this unusual species with molecular hydrogen in the gas phase. This slows down the ultrafast fluxional process which so far prevented the recording of vibrational spectra. The cluster ions CH5" (H2)n (n = 1, 2, 3), after mass selection by an ion trap, were then subjected to IR laser spectroscopy/quadrupol mass spectrometry which ultimately yielded the IR absorption. [40] And the benzene cation, formed by removal of one electron from the parent hydrocarbon was shown to possess Deh symmetry by rotation resolved ZEKE-photoelec-tron spectroscopy (Zero Tinetic Energy-PES). [41]... 

Van der Flage and co-workers [280] combined MALDI and Fourier transform ion cyclotron mass spectrometry (FT-ICR-MS) for the characterisation of polyoxyalkyleneamines. MALDI FT-ICR-MS was used to resolve intact, sodium ion cationised oligomer ions in the mass range from m/z 500 to 3500. NMR was used to measure the average end-group distribution to provide insight into conformational differences. In this respect, FT-ICR-MS and NMR data were complementary. Combined results yielded detailed information about chemical composition distributions of polyalkyleneamines that hitherto it was not possible to obtain with either technique separately. Merits and limitations of the data produced with MALDI FT-ICR-MS are discussed and compared with those of H and C NMR data [280]. 

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