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  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 10 (1975), S. 867-873 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Composite metastable peaks are generated in the unimolecular fragmentations (i) [C3H5]+ → [C3H3]+ + H2 (flat-top upon flat-top) and (ii) [C4H9]+ → [C3H5]+ + CH4 (flat-top and gaussian). The measurement of appearance potentials and kinetic energy releases lead us to conclude, in agreement with earlier proposals, that in (i) the components can arise from the generation of the isomeric cyclopropenium and propargyl daughter cations. In (ii) the components are proposed to arise from the fragmentation of tert- and sec-butyl cations yielding allyl as the common daughter ion.The composite peak observed in the fragmentation (iii) [C3H4]+· → [C3H3]+ + H· is shown to be present only if the decomposing molecular ion is large enough to also produce [C6H8]2+ ions. The second component in (iii) then arises from the reaction [C6H8]2+ → [C6H6]2+ + H2.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 16 (1981), S. 236-236 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 13 (1978), S. 133-134 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dish-topped metastable peak for the fragmentation [C3H7]+ → [allyl]+ + H2 is generated by the threshold fragmentation. The fraction of the reverse activation energy which is partitioned as translational energy of the products is 0.9 ± 0.1. It is proposed that a similar partitioning coefficient applies to the excess internal energy above threshold.
    Additional Material: 1 Ill.
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  • 4
    Publication Date: 2011-08-24
    Description: Results of observations of the carbon star TX Psc at high resolution in the 4000/cm spectral region and at moderate resolution from 2500 to 8000/cm are reported. The opacity sampling technique is employed to present model atmospheres of carbon stars with normal solar oxygen abundance and deep envelope composition that include HCN and C2H2. The oxygen abundance of TX Psc is found to be more accurately represented by a deep envelope composition depleted in oxygen by roughly two orders of magnitude than by a solar oxygen abundance. Polyatomic opacities influence the CO line depths and the derived oxygen abundance as a second-order effect. Polyatomic bands appear to be far too strong in the models, implying the need for another source of opacity to backwarm the outer atmosphere and thereby limit the polyatomic band depths. Dust, rather than polyatomic molecules, is a candidate for the backwarming opacity.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 402; 2; p. 680-693.
    Format: text
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  • 5
    Publication Date: 2019-06-28
    Description: Motivated by recent work which hints at a possible deficiency of hydrogen in non-Mira N-type carbon stars and to further explore the parameter space of chemical composition, computations have been made of a series of hydrogen-deficient models for carbon stars. For these models Teff = 3000 K, and log g = 0.0. Solar abundances are used for all elements except for carbon (which is enhanced to give C/O = 1.05), hydrogen, and helium. As the fractional abundance of hydrogen is decreased, being replaced by helium, the temperature-optical depth relation is affected only slightly, but the temperature-pressure relation is changed. The most striking change in the emergent flux is the decrease of the H(-) peak at 1.65 micron compared with the blackbody peak at 1.00 micron.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 292; 228-230
    Format: text
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