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  • 1
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 75-89 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The high-resolution infrared spectrum of 1-chloro-2-fluoroethane in a molecular beam was collected over the 2975–2994 cm−1 spectral region. The spectral region of 2975–2981 cm−1 contains a symmetric C–H stretching vibrational band of the gauche conformer containing the 35Cl isotope. The spectral region of 2985–2994 cm−1 contains three vibrational bands of the trans conformer. Two of the three bands are assigned as an antisymmetric C–H stretch of each of the two different chlorine isotopes. The third band is assigned as a symmetric C–H stretch of the 35Cl isotope. The gauche conformer of 1-chloro-2-fluoroethane showed doublet patterns similar to those previously observed in 1,2-difluoroethane. The model for 1,2-difluoroethane is further refined in the present work. These refinements suggest that the coupling dark state in 1,2-difluoroethane is composed of 1 quantum C–H bend, 1 quantum C–C stretch, and 12 quanta of torsion. For 1-chloro-2-fluoroethane the dark state could not be identified due to a small data set. The trans conformer of 1-chloro-2-fluoroethane showed no evidence of mode coupling in the three vibrational bands. Including 2-fluoroethanol in this series of molecules, the extent of vibrational mode coupling did not correlate with the density of states available for coupling. Therefore, density of states alone is insufficient to explain the observed trend. A correlation was observed between the degree of intramolecular interaction and vibrational mode coupling. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 831-839 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Microwave/radio-frequency-infrared multiple resonance has been used with an electric-resonance optothermal spectrometer to characterize a weak 21.6 MHz perturbation in the infrared spectrum of the ν14 C–O stretching vibration of 2-fluoroethanol. The infrared spectrum of 2-fluoroethanol was recorded at a resolution of ∼2 MHz using a tunable microwave-sideband CO2 laser. The spectrum is fit by an asymmetric-rotor Hamiltonian to a precision of 0.6 MHz, except for the transitions to the 413 upper state which are split into doublets by an interaction between the 413 level and a rotational level of a nearby background, or dark, vibrational state. Microwave/radio-frequency-infrared double and triple resonance reveals that the 413 level of the C–O stretching vibration is interacting with the 431 level of the dark state. The rotational constants determined for the dark state allow us to assign the perturbing state to the ν18+4ν21 combination vibration of the lowest energy conformer, where ν18 is the CCO bending vibration and ν21 is the C–C torsional vibration. From the weak ΔKa=2 matrix element between ν14 and ν18+4ν21 it is possible to derive a J=0 anharmonic interaction between these states of ∼3.5 GHz.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 145-154 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Optothermal detection has been used to observe nonradiative relaxation channels in aniline, p-bromoaniline, and trans-stilbene. p-Bromoaniline has no detectable fluorescence due to a heavy atom effect which increases the rate of intersystem crossing to the triplet state. An optothermal spectrum of p-bromoaniline was observed with the origin at 32 625 cm−1. For trans-stilbene, the differences between the laser excitation spectrum and the optothermal spectrum of the S1 state clearly show the onset of isomerization at ∼1250 cm−1 above the origin. Absolute quantum yields of fluorescence, Franck–Condon factors, nonradiative rates, and radiative rates have been obtained for a series of vibronic transitions. For low energy vibrational states, there is good agreement between the current study and previous work. For vibrational energies above the barrier of isomerization, predicted quantum yields do not agree with our experimental results. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    s.l. : American Chemical Society
    Industrial & engineering chemistry 45 (1953), S. 529-532 
    ISSN: 1520-5045
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    s.l. : American Chemical Society
    Industrial & engineering chemistry 50 (1958), S. 125-128 
    ISSN: 1520-5045
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5486-5493 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Three-point bounds on the effective conductivity σe of isotropic two-phase composites, that improve upon the well-known two-point Hashin–Shtrikman bounds [J. Appl. Phys. 23, 779 (1962)], depend upon a key microstructural parameter ζ2. A highly accurate approximation for σe developed by Torquato [J. Appl. Phys. 58, 3790 (1985)] also depends upon ζ2. This paper reports a new and accurate algorithm to compute the three-point parameter ζ2 for dispersions of hard spheres by Monte Carlo simulation. Data are reported up to values of the sphere volume fraction φ2 near random close-packing and are used to assess the accuracy of previous analytical calculations of ζ2. A major finding is that the exact expansion of ζ2 through second order in φ2 provides excellent agreement with the simulation data for the range 0≤φ2 ≤0.5, i.e., this low-volume-fraction expansion is virtually exact, even in the high-density region. For φ2 〉0.5, this simple quadratic formula is still more accurate than other more sophisticated calculations of ζ2. The linear term of the quadratic formula is the dominant one. Using our simulation data for ζ2, we compute three-point bounds on the conductivity σe and Torquato's approximation for σe .
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1948-1955 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Improved rigorous bounds on the effective elastic and transport properties of a transversely isotropic fiber-reinforced material composed of oriented, infinitely long, multisized circular cylinders distributed throughout a matrix are computed. Specifically, we evaluate such bounds on the effective axial shear modulus (which includes, by mathematical analogy, the transverse conductivity), effective transverse bulk modulus, and the effective transverse shear modulus. These are generally demonstrated to provide significant improvement over the Hill–Hashin bounds which incorporate only volume-fraction information. Although the upper bounds diverge from the lower bounds when the cylinders are much stiffer than the matrix, the improved lower bounds still yield relatively accurate estimates of the effective properties. Generally, increasing the degree of polydispersivity in cylinder size increases the effective transverse conductivity (or axial shear modulus) and effective transverse bulk modulus, and decreases (slightly) the effective transverse shear modulus for cases in which the fibers are more conducting or stiffer than the matrix.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    s.l. : American Chemical Society
    Journal of the American Chemical Society 70 (1948), S. 900-903 
    ISSN: 1520-5126
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    s.l. : American Chemical Society
    Journal of the American Chemical Society 63 (1941), S. 1013-1017 
    ISSN: 1520-5126
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    s.l. : American Chemical Society
    Journal of the American Chemical Society 63 (1941), S. 1405-1411 
    ISSN: 1520-5126
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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