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  • 1995-1999  (2)
  • 1999  (2)
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  • 1995-1999  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 8535-8544 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Nucleation rate data, obtained from expansion wave tube experiments, are reported for several vapor–gas mixtures at high pressure. Results are given for water–vapor in the presence of helium and nitrogen gas, and for n-nonane in helium and methane. For all these mixtures, carrier gas pressures of 10, 25, and 40 bar have been applied, with temperatures ranging from 230 to 250 K. An extended form of the nucleation theorem (in terms of the derivative of the nucleation rate with respect to carrier gas pressure) is derived, which appears to be very helpful in the interpretation of high pressure data. It can be used to obtain the carrier gas content of the critical nucleus directly from the pressure dependence of experimental nucleation rates. Combining this method with the theoretical considerations of part I of this paper [J. Chem. Phys. 111, 8524 (1999), preceding paper]: the nucleation behavior of water at high pressures of both helium and nitrogen can quantitatively be understood. For n-nonane in helium our "pressure perturbation approach" is also valid. For n-nonane in methane, however, this approach fails because of the high methane solubility in the liquid phase. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 8524-8534 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A theoretical approach is presented that accounts for the influence of high pressure background gases on the vapor-to-liquid nucleation process. The key idea is to treat the carrier gas pressure as a perturbation parameter that modifies the properties of the nucleating substance. Two important mechanisms are identified in this respect: With increasing carrier gas pressure, the saturated vapor density tends to increase (enhancement effect), whereas the surface tension generally decreases. Several routes to obtain data for these pressure effects are outlined, in particular for the vapor–gas mixtures that have been studied experimentally. (The results of these expansion wave tube experiments are presented in Paper II of this paper [J. Chem. Phys. 111, 8535 (1999), following paper.]) Using classical nucleation theory, a criterion is then derived for the "pressure perturbation" approach to be valid: xgeq(very-much-less-than)(S−1)/S, where xgeq is the carrier gas solubility in the liquid phase, and S is the supersaturation ratio. For the semiphenomenological Kalikmanov–Van Dongen model, the implications of the enhancement effect and surface tension decrease are briefly discussed. We also illustrate how these two effects can be obtained from (binary) density functional theory. Results of the latter for a mixture of Lennard-Jones particles are presented, with potential parameters that are characteristic for n-hexane with several carrier gases. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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