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  • Copernicus  (15)
  • Wiley-Blackwell  (10)
  • American Institute of Physics (AIP)  (7)
  • 2010-2014  (16)
  • 1985-1989  (16)
  • 1
    Electronic Resource
    Electronic Resource
    Line broadening, line shifting, and line coupling effects on N2–H2O stimulated Raman spectra (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5916-5925 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In order to understand the influence of H2O on the stimulated Raman Q-branch spectra of nitrogen in combusting media, an exhaustive theoretical and experimental study has been carried out. Starting from a semiclassical model, particularly convenient at high temperature, the Q-line broadening and shifting coefficients have been calculated over a wide temperature range and for a large number of lines. Stimulated Raman Spectra (SRS) measurements have allowed us to test these calculated line broadening coefficients and thus establish the high accuracy of semiclassical values. The theoretical broadening coefficients have been inverted to deduce state-to-state rotational relaxation rates by using two types of fitting laws. A partial test of the resulting Q-branch profiles has been realized at moderate pressures leading to a discrimination between these two laws. Furthermore, the effect of rotational energy transfers on collisionally narrowed profiles at higher densities has been simulated and compared with the pure N2 case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457461
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  • 2
    Electronic Resource
    Electronic Resource
    Measurements and calculations of CO2 room-temperature high-pressure spectra in the 4.3 μm region (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 2944-2950 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Measurements of the absorption by pure CO2 in the 4.3 μm region are presented. They refer to the temperature of 291 K and densities in the 1–80 amagat range. Calculations based on the addition of Lorentzian contributions strongly overestimate the absorption since they do not account for line overlapping. The energy corrected sudden approximation (ECSA) is used to model line mixing within the impact approximation. The scaling parameters of this model are deduced from line-broadening data. This calculation strongly underestimates the absorption in the spectral region near the edges of the vibrational band, whereas it overestimates the absorption in the far wings of the lines. This is attributed to the impact approximation which does not account for the frequency dependence of the relaxation operator. This dependence is roughly determined from our results; it is in good qualitative agreement with the few corresponding available results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455894
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  • 3
    Electronic Resource
    Electronic Resource
    Collisional broadening of rotation–vibration lines for asymmetric-top molecules. II. H2O diode laser measurements in the 400–900 K range; calculations in the 300–2000 K range (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 144-156 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Numerous comparisons between predictions of the model presented in part I of this paper and experimental H2O infrared linewidths are presented. It is shown that our model, contrary to those used up to now, gives accurate results for H2O room-temperature line broadening by O2 and Ar, and for high rotational quantum-number lines by N2. First accurate experimental widths and intensities of some H2O ν2-band lines in the 400–900 K temperature range are also presented. Detailed analysis of the data demonstrates the great influence of a "resonance overtaking'' mechanism. The latter results from the modifications of both the perturber rovibrational population distribution and kinetic energy with temperature; it strongly enhances the contributions of the collision-induced rotational transitions involving significant energy jumps. This mechanism is well accounted for by our model and quantitatively explains the unusually slow decrease of some linewidths with temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452605
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  • 4
    Electronic Resource
    Electronic Resource
    Collisional broadening of CO2 IR lines. II. Calculations (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 2999-3006 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The ability of available theoretical models in describing broadening mechanisms is tested for the CO2–O2, CO2–CO2, and CO2–N2 systems. It is shown that the Anderson–Tsao–Curnutte theory is inaccurate since short-range forces can contribute significantly to broadening. We use the approach of Robert and Bonamy, but the usual expansion of the atom–atom potential to the fourth order around the intermolecular distance appears insufficient at short distances for these particular systems. We propose a better representation of the radial dependence of the atom–atom potential, while keeping the previous analytical expression of the cross section. Satisfactory results are obtained for both the rotational quantum number dependence of room-temperature CO2–O2, CO2–CO2, and CO2–N2 half-widths and the evolution of CO2–N2 broadening with temperature. It is shown that the isotropic part of the potential involved in the trajectory calculation must be coherently deduced from the atom–atom interaction potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453941
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  • 5
    Electronic Resource
    Electronic Resource
    Collisional broadening of rotation–vibration lines for asymmetric-top molecules. III. Self-broadening case; application to H2O (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 2781-2789 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A semiclassical theory of asymmetric-top molecule line broadening, developed in part I of this series of papers for linear perturbers, is extended to asymmetric-top perturbers. This model has been successfully applied in part II to the broadening of H2O lines by N2, O2, and Ar. The present applications to the self-broadening of H2O infrared and Raman lines in the 300–900 K range also show the quality of the model. Due to the high electrostatic forces involved in the H2O–H2O interaction, the short-range anisotropic potential has little influence. Nevertheless, the need for a modeling of the trajectory is demonstrated, mainly in the case of high rotational quantum number lines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453065
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  • 6
    Electronic Resource
    Electronic Resource
    Collisional broadening of rotation–vibration lines for asymmetric top molecules. I. Theoretical model for both distant and close collisions (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 4256-4267 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A semiclassical theory of infrared linewidths in the gas, previously developed for linear molecules, is extended to asymmetric top molecules. It includes a satisfactory treatment of the close collisions and is consequently adapted to describe the temperature dependence of the linewidths, in particular in the combustion temperature range. Numerical applications to the water vapor perturbed by nitrogen, oxygen, and argon show strong different behaviors following the nature of the perturber. For oxygen and argon perturbers, the contribution of close collisions is the predominant mechanism of line broadening. The consistency of the theoretical model is evidenced by comparison with precise measurements for H2O–N2, –O2, and Ar at 300 K. Moreover, the calculated temperature dependence of the linewidths is compared with recent experimental data for H2O–Ar between 1300 and 2300 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450047
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  • 7
    Electronic Resource
    Electronic Resource
    Morphologische Untersuchungen an Polymergelen und zum Sol-Gel-Übergang mittels Gefrierätzung. 3. Mitt.: Ionotrope Gelbildung mit Carboxymethylcellulose2. Mitt.: Acta Polymerica 38 (1987) 103 (1987)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 38 (1987), S. 176-184 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Employing the freeze-etching technique, the morphology of formation of ionotropic gels precipitated from aqueous Na-carboxymethyl cellulose solution by La+++, Pb++ and Al+++ ions has been investigated. Special attention is given to the early stages of the formation of capillary voids. After formation of a dense granular gel-layer between polymer solution and precipitant, capillary formation obviously starts from local changes of polymer concentration having a certain amount of regularity. In the further process of structural differentiation of the capillary voids the polymer matrix is desolvated and ordered into a fibrillar network. Assets and limitations of morphological investigations for elucidating the mechanism of ionotropic gel formation are discussed.
    Notes: Unter Anwendung der Gefrierätztechnik wurde die Bildung ionotroper Gele durch Fällung wäßriger Na-Carboxy-methylcellulose-Lösungen mit La+++-, Pb++- und Al+++-Ionen morphologisch untersucht. Besondere Aufmerksamkeit wurde dabei dem Anfangsstadium der Kapillarbildung gewidmet. Nach Ausbildung einer dichten partikularen Gelgrenzschicht zwischen Polymerlösung und Fällmittel wird die Kapillarbildung offenbar durch örtliche Konzentrations-änderungen der Polymerlösung eingeleitet, die eine gewisse Regelmäßigkeit aufweisen. Im weiteren Prozeß der Strukturdifferenzierung der kapillaren Hohlräume ordnet sich die Polymermatrix unter Desolvatisierung zu einem fibrillaren Netzwerk. Möglichkeiten und Grenzen morphologischer Untersuchungen zur weiteren Klärung des Mechanismus der ionotropen Gelbildung werden diskutiert.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1987.010380306
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  • 8
    Electronic Resource
    Electronic Resource
    Polymer Wear and Its Control. Hg. von Lieng-Hitang Lee. ACS Symposium Series 287. ISBN 0-8412-0932-4. Washington, D.C.: American Chemical Society 1985. 421 S., geb. US $ 95.95. (1987)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 38 (1987), S. 407-408 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1987.010380626
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  • 9
    Electronic Resource
    Electronic Resource
    Morphologische Untersuchungen an Polymer-Gelen und zum Sol-Gel-Übergang mittels Gefrierätzung. 1. Mitt.: Zielstellung und Gefrierätz-Strukturen der Ausgangslösungen (1987)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 38 (1987), S. 56-66 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: By applying the freeze-etching technique with different rates of cooling the solid state morphology of glycerol/H2O- and DMSO/H2O-systems, of aqueous electroyte solutions, and of aqueous and some non-aqueous polymer solutions were compared. At a high cooling rate, granular structures are obtained with aqueous polymer solutions, which are interpreted to be single polymer coils or aggregates of macromolecules. At a lower rate of cooling, lamellar or cellular structures are observed, which are discussed on the basis of “constitutional supercooling” known from the solidification of binary metallic systems.
    Notes: Mittels Gefrierätztechnik wurden bei unterschiedlicher Abkühlgeschwindigkeit die Erstarrungsmorphologien von Glycerol/H2O- und DMSO/H2-Gemischen, von wäßrigen Elektrovlytlösungen und von wäßrigen sowie einigen nichtwäßrigen Polymerlösungen verglichen. Bei hoher Abkühlgeschwindigkeit werden im Falle wäßriger Polymerlösungen partikulare Strukturen erhalten, die als einzelne Molekülknäuel gedeutet werden. Bei geringerer Abkühlgeschwindigkeit werden lamellare bzw. zellulare strukturen beobachtet, zu deren Diskussion das vom Erstarren binärer Metallegierun gen her bekannte Konzept der “konstitutionellen Unterkühlung” herangezogen wird.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1987.010380112
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  • 10
    Electronic Resource
    Electronic Resource
    Morphologische Untersuchungen an Polymergelen und zum Sol-Gel-Übergang mittels Gefrierätzung. 2. Mitt.: Gelbildung durch Phasenïnversion am beispiel des Celluloseacetats1. Mitt.: Acta Polymerica 38 (1987) 56 (1987)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 38 (1987), S. 103-107 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Applying the freeze-etching technique, the morphology of cellulose acetate gels precipitated by water from solutions in DMSO was investigated with electron microscopy. Special attention has been given to the initial states of gel formation. Within the dense, granularly structured border area of the gel to the side of the precipitant the smallest particles are found at the precipitant side. The volume phase of the gel shows a fibrillar network structure with voids filled by the precipitant. Within the transition range between gel and polymer solution local domains of beginning phase separation are observed, which show a rather high precipitant or a high polymer content. The applicability of the concept of spinodal phase separation is discussed.
    Notes: Unter Anwendung der Gefrierätztechnik wurde die Morphologie der durch Fällung mit Wasser aus einer Lösung in DMSO erhaltenen Koagulationsstrukuren von Celluloseacetat elektronemikroskopisch untersucht. Besondere Aufmerksamkeit wurde dem Anfangsstdium der Gelbildung gewidmet. In der partikular aufgebauten dichten Gelgrenzschicht zur Fällmittelseite befinden sich die kleinsten Teilchen auf der Fällmittelseite. Die Volumenphase des Gels weist eine fibrillare Netzwerkstruktur mit Fällmittel-gefüllten auf. Im Übergangsbereich zwischen Gel und Polymerlösung sind lokale Fällmittel-reiche und Polymer-reiche Entmischungsbezirke zu erkennen. Die Anwendbarkeit des Konzepts der spinodalen Entmischung wird diskutiert.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1987.010380201
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