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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 272-280 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Using synchrotron radiation as a continuum light source, the absolute photoabsorption and direct dissociation cross sections of C2 H2 in the 1530–1930 A(ring) region have been measured at 295 and 155 K. In comparison with cross sections obtained at room temperature, the cross sections at absorption peaks typically increase by 10%–40% while those at absorption valleys decrease by as much as 30% at 155 K. Further, the absorption band profiles become narrower as the gas temperature decreases. In the presently studied wavelength region, there are at least three electronic states, namely, the A˜ 1 Au , the B˜ 1 Bu , and a continuum. Using the present low temperature data we have constructed the repulsive potential energy curve of the direct dissociation state according to the Franck–Condon principle. The potential energy curve thus constructed can be more accurate than that constructed by using room temperature cross section data because only the absorption cross section from the ν'=0 level contributes. The present cross section data have also been used in the analysis of oscillator strength distribution.
    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 88 (1988), S. 5237-5238 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 6275-6282 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The various absolute partial cross sections for producing the excited neutral fragments, OH(A 2Σ+), H(n=2–4), and H2(a 3Σ+g), from photoexcitation of H2O in the 15–20.5 eV region are presented. It is found that a large fraction of the neutral products which amounts to 0.35 in the 15.7–17.7 eV region can be attributed to the undetected neutral products of (1) H(n=1)+OH(X 2Π), (2) H2(X 1Σ+g)+O(1D), and (3) H2(X 1Σ+g)+O(1S). All these products will possess high kinetic energy. The present results clearly show strong competitions among processes leading to photoionization and various photodissociation processes.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 498-499 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 1713-1717 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The kinetic energy distributions of excited hydrogen atoms produced in the dissociative photoionization excitation of H2 by He II 304 A(ring) photons have been obtained. A fluorescence photon–photoion coincidence technique has been utilized in the present study. A coincidence spectrum showing a broad peak with a weak shoulder corresponding to a time delay of 5.6–7.5 μs is obtained. The kinetic energy distribution of the peak is between 1.2 and 7.5 eV with a maximum at 4.2 eV indicating that this peak is attributable to the lowest energy dissociative photoionization excitation processes which correlate with H(2l)+H+. The relative partial cross sections for direct dissociative photoionization excitation through the 2pπu and 2sσg states at 304 A(ring) are determined to be 1: 0.25.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 5524-5526 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The cross section for production of the H2O+ A˜ 2A1(0,7,0)→X˜ 2B1(0,0,0) fluorescence through photoionization of H2O has been measured in the 14.5–20.5 eV region. The maximum quantum yield is 1.4×10−3 at 16.5 eV. Further, the cross sections for producing the H2O+[A˜ 2A1(0,7,0)] and H2O+ A˜ 2A1 have been estimated. The magnitude of the latter is about a factor of 10 smaller than that obtained by electron spectroscopy. The discrepancy can be attributed to radiationless transitions between the A˜ and X˜ states of H2O+.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 5584-5586 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The NH(A→X) emission produced by photodissociation of NH3 has been investigated by utilizing a line emission source in the 600–1340 A(ring) region. The production of the NH (A 3Πi) photofragment involves a spin-forbidden transition. The fluorescence quantum yields for producing NH (A→X) fluorescence are less than 2×10−3 at wavelengths longer than 976 A(ring).
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 4495-4499 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Using synchrotron radiation as a continuum background, the absolute total absorption cross section of C2H2 has been measured using a double ionization chamber. The cross sections range from 2.5 to a maximum of 35 Mb in the 175–740 A(ring) region. Two new Rydberg series have been identified and apparently converge to the B˜ 2Σ+u state of C2H+2 at 18.71 eV. The observed Rydberg states are tentatively assigned to (2σu)−1 nsσg 1Σ+u and (2σu)−1 ndσg 1Σ+u, respectively. The present cross section data have been used in the analysis of various sum rules including the TRK sum rule.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 4093-4094 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photoabsorption and photoionization spectra of ethylene have been shown to exhibit weak broad structures in the spectral region between the ionization threshold and 1060 A(ring). Some members of three Rydberg series that converge to the first excited electronic state A˜(2B3) of C2H+4 have been identified. They have been tentatively assigned as transitions from the ground state to the 4sσ-, 4pσ-, 3d-, and 4d-Rydberg states. The C2H4 molecule is suggested to be twisted in at least the 4sσ- and nd-Rydberg states.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 267-273 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High resolution photoabsorption cross section data for the CO 4PG (1,0) band have been obtained under several different temperature conditions. It was found that the absorption strength of the d 3Δ1–X 1Σ+ (5,0) band underlying the 4PG (1,0) band varies with temperature. The ratio of the absorption band strength of the d–X (5,0) band to that of the 4PG (1,0) band has been determined for temperatures at 150 K, 295 K, and 370 K. Adopting the integrated oscillator strength of the 4PG (1,0) from the recent literature we have determined band absorption cross sections for the two bands as a function of temperature. The ratios of the band absorption strengths of the A–X (1,0) and d–X (5,0) bands at different temperatures are compared with those calculated from the mixing coefficients determined by analysis of level shifts in high resolution spectra and lifetime measurements. © 1999 American Institute of Physics.
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