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  • 1
    Electronic Resource
    Electronic Resource
    Erratum: "Homogeneous nucleation rates for water" [J. Chem. Phys. 99, 4680 (1993)] (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 8205-8206 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481368
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  • 2
    Electronic Resource
    Electronic Resource
    Measurement of the molecular content of binary nuclei. II. Use of the nucleation rate surface for water–ethanol (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 6062-6072 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In a preceding paper we determined the molecular contents of binary nuclei from homogeneous nucleation rate measurements studing ethanol–hexanol as a nearly ideal model system. Here we report the analogous measurements for the nonideal water–ethanol system known from previous investigations to display surface enrichment of ethanol in the nuclei. The nucleation pulse technique applied allows accurate measurements of homogeneous nucleation rates in the range 105〈J/cm−3 s−1〈109. We determined the homogeneous nucleation rates of mixed droplets in supersaturated water–ethanol vapor mixtures with argon as the carrier gas. The experiments were performed as functions of the water and ethanol gas phase activities, a1 and a2, respectively, ranging from pure water to pure ethanol with ten intermediate activity ratios at T=260 K. The experimental data shape a nucleation rate surface in three-dimensional J–a1–a2 space from which the critical activities for a rate of Jc=107 cm−3 s−1 were determined. The critical activities are compared with the predictions of the classical binary nucleation theory. The observed large discrepancies can be attributed to very water-rich compositions of the nuclei predicted by the theory. The results support previous findings for the water-n-propanol system, where even larger discrepancies were observed. In a next step the individual numbers of ethanol and water molecules in the nuclei are directly determined from the slopes of the experimental nucleation rate surface. The observed variations of the molecular numbers with vapor phase composition differ substantially from that of an ideal mixture. Comparing the measured nucleus compositions to the predictions of a recently proposed explicit cluster model one observes an almost quantitative agreement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467117
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  • 3
    Electronic Resource
    Electronic Resource
    Measurement of the molecular content of binary nuclei. III. Use of the nucleation rate surfaces for the water-n-alcohol series (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 4333-4345 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In two preceding papers the molecular content of binary ethanol-hexanol and water-ethanol nuclei, respectively, was determined from nucleation rate measurements. While nucleation of ethanol-hexanol mixtures behaved nearly ideal, a strong mutual nucleation enhancement for water-ethanol was observed. Here we extend the investigations to include the longer chain alcohols, that is water −CiH2i+1OH systems with i=2 to 6. Using the nucleation pulse technique developed in the past few years nucleation rates in the range 105〈J/cm−3 s−1〈109 are measured. Ranging from pure water to pure alcohol the water and alcohol activities, a1 and a2, respectively, are varied for each system with about ten intermediate compositions at constant temperature T=260 K. Aside from a remarkably similar behavior of the various alcohols, one observes that with increasing alcohol chain length the mutual nucleation enhancement decreases. Since all water-alcohol systems behave qualitatively similar, we confine ourselves to present the full experimental nucleation rate surface J(a1,a2) for one system, water-n-pentanol, as an example. From the nucleation rate surface for each system the onset activities corresponding to a reference nucleation rate of J0=107 cm−3 s−1 are determined. From the slopes of the nucleation rate surfaces one obtains the individual numbers of molecules in the critical cluster ni* because ∂ ln J/∂ ln ai≈ni*. As noted previously, determining the molecular content this way does not involve any particular theoretical model, nor does it depend on the structure of the critical cluster. Accordingly, the average composition of the critical clusters can be obtained. An alcohol enrichment of the nuclei at low alcohol activity fraction is found for all alcohols examined, the degree diminishing with increasing alcohol chain length. The appearance of a macroscopic miscibility gap for the higher alcohols is not reflected in any qualitative change of the composition of the microscopic nuclei. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470672
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  • 4
    Electronic Resource
    Electronic Resource
    Homogeneous nucleation rates for n-butanol (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 7835-7843 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Homogeneous nucleation rates of n-butanol in argon were measured in an expansion chamber maintaining pressure, temperature, and vapor supersaturation practically constant during nucleation periods of about 1 ms. Tables of the homogeneous nucleation rates J in the range 105〈J/cm−3 s−1〈109 as function of supersaturation S in the temperature range 225〈T/K〈265 are presented along with the other experimental measurables. For the temperatures considered the equilibrium vapor pressure of n-butanol and the surface tension are known with sufficient accuracy. Accordingly, a quantitative comparison of the experimentally obtained nucleation rates with the predictions of the classical theory could be performed. The agreement is sufficient. The reported individual J−S curves were obtained at selectable constant temperatures. From the slopes of the isothermal J−S curves the number of molecules in the critical clusters were determined without reference to any specific nucleation theory. Conceiving the clusters as small droplets one finds, using macroscopic liquid density and surface tension, that the Gibbs–Thomson equation provides remarkably good predictions even for droplets with radii down to 10 A(ring).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468208
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  • 5
    Electronic Resource
    Electronic Resource
    The Problem of Measuring Homogeneous Nucleation Rates and the Molecular Contents of Nuclei: Progress in the Form of Nucleation Pulse Measurements (1994)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 7748-7758 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100083a003
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  • 6
    Electronic Resource
    Electronic Resource
    Measurement of the molecular content of binary nuclei. IV. Use of the nucleation rate surfaces for the n-nonane-n-alcohol series (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 4257-4266 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In a previous paper the molecular content of binary water-n-alcohol nuclei has been determined from nucleation rate measurements. A strong mutual enhancement of water and alcohol in forming the nuclei was observed, although macroscopically the higher alcohols are only partially miscible with water. In this paper we replace water by n-nonane, that is, we examine n-nonane-CiH2i+1OH systems with i=2–6. Using the nucleation pulse technique nucleation rates in the range 105〈J/cm−3 s−1〈109 are measured. Ranging from pure n-nonane to pure n-alcohol the n-nonane and n-alcohol activities, a1 and a2, respectively, are varied for each system with about eight intermediate compositions at a constant temperature of T=230 K. A rather reluctant conucleation of the n-alcohols with n-nonane is found, the most stubborn being ethanol. However, one observes that with increasing alcohol chain length the nucleation process tends to become more ideal. We present the full experimental nucleation rate surface J(a1,a2) for n-nonane-n-propanol as an example. From the nucleation rate surface for each system the onset activities corresponding to a reference nucleation rate of J0=107 cm−3 s−1 are determined. From the slopes of the nucleation rate surfaces one obtains the individual numbers of molecules in the critical cluster ni*(approximate)∂ ln J/∂ ln ai. As noted previously, determining the molecular content this way does not involve any particular theoretical model, nor does it depend on the structure of the critical cluster. Accordingly, the average composition of the critical clusters is obtained. An alcohol depletion of the nuclei at low alcohol activity fraction is found for all alcohols examined, the degree diminishing with increasing alcohol chain length. Macroscopically all alcohols are miscible with nonane. Similarly, a depletion of n-nonane in the nuclei is observed at low n-nonane activity fractions. The approach towards a macroscopic miscibility gap for the shorter alcohols is reflected in quantitative but no qualitative changes of the composition of the microscopic nuclei. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475825
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  • 7
    Electronic Resource
    Electronic Resource
    Composition of critical clusters in ternary nucleation of water–n-nonane–n-butanol (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 8293-8299 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In previous papers the determination of the molecular contents of critical clusters has been performed. Both unary and binary vapor mixtures have been examined. This paper describes the first study of a ternary system. Using a nucleation pulse chamber accurate measurements of homogeneous nucleation rates (105〈J/cm−3 s−1〈109) of mixed droplets in supersaturated, ternary mixtures of water, n-nonane and n-butanol vapor have been performed. The examined gas phase activities, a1, a2, and a3, respectively, covered the whole ternary composition space at T=240 K. The observed variations of the cluster compositions with vapor phase composition differ substantially from that of ideal mixtures. The experiments seem to indicate phase separation within the critical clusters. The arrangement of the molecules in the cluster remains to be clarified. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472683
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  • 8
    Electronic Resource
    Electronic Resource
    Homogeneous nucleation rates for n-pentanol in argon: Determination of the critical cluster size (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 5181-5187 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have measured homogeneous nucleation rates of n-pentanol droplets in argon using the nucleation pulse chamber recently described. The nucleation rates J were measured as functions of activity a at constant temperatures in steps of about 2.5 K for 241.8〈T/K〈271.0. The experimental data were compared with the predictions of the so-called self-consistent classical nucleation theory containing an additional exp(aitch-theta)/a factor. Smaller systematic deviations of the predictions of the theory from the experimental onset activities were observed than previously for other systems. Using a simple, alternative derivation of the so-called nucleation theorem we, furthermore, determined the average size of the critical cluster (n*) from the slopes of the isothermal J–a curves. We found that the self-consistent classical nucleation theory systematically overestimates the experimental n*'s. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471145
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  • 9
    Electronic Resource
    Electronic Resource
    Measurement of the molecular content of binary nuclei. Use of the nucleation rate surface for ethanol–hexanol (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 4693-4704 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We measured the homogeneous nucleation rates J of mixed droplets in supersaturated ethanol–hexanol vapor mixtures in argon as functions of the vapor phase activities a1 and a2 of ethanol and hexanol, respectively. Measurements ranged from pure ethanol to pure hexanol at T=260 K. The experimental nucleation rate curves shape a nucleation rate surface in the three-dimensional J−a1−a2 space. We develop a theory for obtaining the average size and composition of a nucleus from this surface determined experimentally. Following this procedure experimental nucleus compositions are determined. This theory is then combined with our measurements in order to determine the makeup of the binary ethanol–hexanol nuclei. Results are compared with the predictions of classical binary nucleation theory. Qualitatively similar trends are observed for the nearly ideal ethanol–hexanol system studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466067
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  • 10
    Electronic Resource
    Electronic Resource
    Homogeneous nucleation rates for water (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 4680-4692 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have investigated homogeneous nucleation of water droplets in the vapor phase. Nucleation in water vapor has been previously studied a number of times using various experimental techniques. The nucleation pulse technique used here allows accurate measurements of homogeneous nucleation rates J vs supersaturation S in the range from 105 to 109 cm−3 s−1. The advance reported here consists of the fact that the J–S curves are measured at a selectable constant temperature. We determined the nucleation rates in supersaturated water vapor mixed with various carrier gases as functions of supersaturation and temperature (217〈T/K〈259). Nucleation is found to be nondependent of the nature of the carrier gas. Data analysis was carried out in four steps. First, we observed quantitative agreement in the range of overlap with experimental results by Miller et al. [J. Chem. Phys. 78, 3204 (1983)]. Second, experimental nucleation rates were compared with the predictions of classical nucleation theory. Systematic deviations from that theory were observed as in the case of other systems (e.g., alcohols, nonane) studied previously. Third, comparison with a new version of Fisher's droplet model reveals remarkable agreement between experiment and theory. Finally, we implemented a model-independent determination of the average nucleus size directly from the slopes of the isothermal J–S curves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466066
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