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  • PACS: 42.62.Fi; 78.40.Me; 78.55.Bq; 79.47.+p  (1)
  • Polymer and Materials Science  (1)
  • egg odor  (1)
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Material
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  • 1
    Electronic Resource
    Electronic Resource
    Intersystem crossing in oligothiophenes studied by fs time-resolved spectroscopy (2000)
    Springer
    Applied physics 71 (2000), S. 443-449 
    Details
    ISSN: 1432-0649
    Keywords: PACS: 42.62.Fi; 78.40.Me; 78.55.Bq; 79.47.+p
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. High triplet quantum yields of more than 90% for bithiophene and terthiophene have to be connected with very fast and effective formation of triplets after excitation. We studied these processes with fs pump–probe spectroscopy. The time behaviour of transient optical spectra within the singlet and triplet manifold was examined for bi- and terthiophene (2T and 3T) in solution. For 2T we used two-photon absorption for excitation. We found transient spectra of the excited singlet state, the triplet state and that of radical cations. The kinetics of the excited-state absorption was described by a bi-exponential function. Additionally we observed formation and recombination of radical cations. The recombination is connected with triplet formation. Both processes could be described by a time constant of 62 ps±9 ps. For 3T we found a dependence of the processes on excitation energy using one-photon absorption. The triplet quantum yield increased with higher excitation energy. The kinetics becomes bi-exponential with increasing amplitude of the short time constant of 2 ps at increasing excitation energy. The main reasons for the effective intersystem crossing (ISC) in both oligothiophenes are – besides the high spin-orbit coupling factor introduced by the sulphur atom – the almost isoenergetic positions of the S 1 and T 2 states, detected by PD-PES [1]. At higher photon excitation energy for 3T above the band gap an additional channel for ISC was detected. We believe that during the geometric change from the non-relaxed non-planar to the relaxed planar excited state S 1, ultrafast intersystem crossing takes place.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003400000352
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  • 2
    Electronic Resource
    Electronic Resource
    Kairomones Used by Trichogramma chilonis to Find Helicoverpa assulta Eggs (2000)
    Springer
    Journal of chemical ecology 26 (2000), S. 359-375 
    Details
    ISSN: 1573-1561
    Keywords: Trichogramma chilonis ; kairomones ; Helicoverpa assulta sex pheromone ; egg odor ; scale odor ; Ostrinia furnacalis sex pheromone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Chemically mediated interactions between an egg parasitoid, Trichogramma chilonis, and its host insect, Helicoverpa assulta, were studied in laboratory experiments. T. chilonis was attracted to the sex pheromone of H. assulta, and, among four components of its sex pheromone, (Z)-11-hexadecenyl acetate seemed to be most attractive. T. chilonis was also highly attracted to (E)-12-tetradecenyl acetate, a component of the sex pheromone of Ostrinia furnacalis, another host. H. assulta eggs were more parasitized by T. chilonis when the eggs were treated with male moth scale extract (MSE) of H. assulta. Parasitism was also affected by the age of the parasitoid, time of day, and MSE concentration. Silica gel chromatography and subsequent argentation chromatography for MSE fractionation indicated the activity was associated with the fraction of saturated hydrocarbons. A linear olfactometer experiment revealed that H. assulta eggs also contain a short-range attractant(s).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005453220792
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The influence of antimony trihalides on flammability and ignitability of polyethylene (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Fire and Materials 15 (1991), S. 127-130 
    Details
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The flammability and ignitability of polyethylene using antimony trihalide compounds as fire retardants was evaluated by standard methods to determine retardant effectiveness. Compared with other retardants, the antimony trihalide compounds, antimony tribromide and antimony trichloride, substantially reduced both the flammability and the ignitability of the polyethylene. The influence of retardant concentration, heat flux and type of polyethylene was also studied.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fam.810150304
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    Paper (German National Licenses)
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