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  • Chemistry  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 21 (1994), S. 298-303 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: It is known that high-molecular-weight, thermally labile molecules can be desorbed intact using keV ion beams. This knowledge has led to numerous applications of fast atom bombardment and secondary ion mass spectrometry (SIMS) by mass spectrometric detection of the desorbed ions. Here we show that these measurements can be enhanced significantly by using resonance-enhanced laser ionization to softly ionize the neutral component of the desorbed flux. This experimental configuration can produce sensitivity improvements of several orders of magnitude over SIMS while adding a certain degree of selectivity to the ionization process itself. Examples of this performance will be presented using a wide variety of molecules, including polycyclic aromatic hydrocarbons, organic polymers, molecular salts and biologically important molecules. Results from model systems to complex samples are discussed, along with their implications for submicron molecular imaging using this technique.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 2
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Multiphoton resonance ionization (MPRI) is used to probe the desorption characteristics of ion-bombarded surfaces of Fe, In and Ni. The effects of primary ion kinetic energy and surface chemistry on the sensitivity and accuracy of MPRI detection are examined. The relative Ni*/Ni° and In2°/In° ratios are found to increase as the energy of the incident Ar+ ion is varied from 300 eV to 1000 eV. A reflecting time-of-flight mass spectrometer is employed to collect efficiently the photoions as well as secondary ions, permitting accurate determination of the ground-state atom fraction and thereby completing a detailed fundamental analysis of the analytical capabilities of the MPRI approach. The ground-state atom fractions are found to parallel changes in surface composition and represent 30-90% of the material desorbed from ion beam-cleaned and air-exposed Fe and In matrices. In contrast, the corresponding secondary ion fractions vary over several orders of magnitude and are difficult to correlate with surface chemistry.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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