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  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 25 (1990), S. 174-180 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of the collision gas on doubly charged ion mass spectra of a selected number of hydrocarbons has been examined. Relative abundances of various product ions in 2E spectra, resulting from charge exchange collisions of doubly charged hydrocarbon ions, do not vary drastically as the collision gas is varied. However, the absolute intensities of these doubly charged ion mass spectra increase significantly when the collision gas is changed from argon to methane to isobutane. Tbese observations are rationalized in terms of a multichannel diabatic curve crossing model.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 26 (1991), S. 892-898 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Positive and negative cluster ions in methanol have been examined using a direct fast atom bombardment (FAB) probe technique. Positive ion (CH3OH)IIH + clusters with n = 1-28 have been observed and their clusters are the dominant ions in the low-mass region. Cluster-ion reaction products (CH3OH)II(H2O)H+ and (CH3OH)II(CH3OCH3)H+ are observed for a wide range of n and the abundances of these ions decrease with increasing n. The negative ion (CH3OH)II(CH3O)- clusters are also readily observed with n = 0-24 and these form the most-abundant negative ion series at low n. The (CH3OH)II(CH2O)-, (CH3OH)II(HIIO)(CH2O)- and (CH3OH)II(H2OXCH3O)- cluster ions are formed and the abundances of these ions approach those of the (CH3OH)II(CH3O)- ion series at high n. Cluster-ion structures and energetics have been examined using semi-empirical molecular orbital methods.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 28 (1993), S. 595-606 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cluster ions from fast atom bombardment of liquid alcohols and nitriles were examined using a continuous-flow technique. Protonated molecular MnH+ species are the dominant cluster ions observed in molecules of formula M. The abundances of the MnH+ cluster ions decrease monotonically with increasing n, and within a homologous series the MnH+ abundance diminishes more rapidly for higher molecular mass compounds. Reaction products (ROH)n(H2O)H+ and (ROH)n(ROR)H+ are observed also in the case of alcohols, and the ion abundances decrease with increasing n. Radiation damage yields fragment ions and ionic alkyl reaction products which are captured in solvent clusters. Semi-empirical molecular orbital methods were used to examine the energetics of cluster ion formation and decomposition pathways. Metastable decomposition processes exhibit only evaporative loss of monomers, with the probability of loss increasing sharply with n. The evaporative ensemble model of Klots was used to predict the cluster size-dependent trends of metastable dissociation processes observed for alcohol and nitrile cluster ions.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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