Electronic Relaxation Processes in Polyatomic Molecules. Progress Report, October 1, 1975--September 30, 1976 PDF Download
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Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Excitation energy dependence of radiationless decay rate under collision-free conditions was utilized as a probe of intramolecular vibrational relaxation in tetracene and pentacene. The results give evidence of vibrational relaxation which competes with electronic relaxation. The substitution dependence of T/sub 1/(n.pi.*) .-->. S/sub 0/ radiationless transition in monocyclic diazines and the temperature dependence of S/sub 1/ non-radiative decay rate in alcoholic solutions of polycyclic monoazines indicate that the vibronic interaction between the lowest energy n.pi.* and .pi pi.* states leads to a rapid radiationless deactivation of the lower of the two electronic states. Finally, a photon-counting spectrofluorometer of very high sensitivity was constructed, and it was used to record T/sub 2/ .-->. T/sub 1/ fluorescence in bromoanthracenes and S/sub 2/ .-->. S/sub 1/ fluorescence in azulene. These spectra represent the first bona-fide, or the most convincing, observation of fluorescence between excited electronic states.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Excitation energy dependence of radiationless decay rate under collision-free conditions was utilized as a probe of intramolecular vibrational relaxation in tetracene and pentacene. The results give evidence of vibrational relaxation which competes with electronic relaxation. The substitution dependence of T/sub 1/(n.pi.*) .-->. S/sub 0/ radiationless transition in monocyclic diazines and the temperature dependence of S/sub 1/ non-radiative decay rate in alcoholic solutions of polycyclic monoazines indicate that the vibronic interaction between the lowest energy n.pi.* and .pi pi.* states leads to a rapid radiationless deactivation of the lower of the two electronic states. Finally, a photon-counting spectrofluorometer of very high sensitivity was constructed, and it was used to record T/sub 2/ .-->. T/sub 1/ fluorescence in bromoanthracenes and S/sub 2/ .-->. S/sub 1/ fluorescence in azulene. These spectra represent the first bona-fide, or the most convincing, observation of fluorescence between excited electronic states.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Experimental and theoretical studies of isotope and substituent effects on T/sub 1/ radiationless decay rates have been carried out as a test of the working hypothesis that vibronic coupling between n.pi.* and .pi pi.* states lead to very efficient radiationless decay from the lower of the two vibronically coupled pair (proximity effect). In addition to providing general support to this hypothesis, the results indicate that isotope effects on spin sublevel decay rates are needed for a stringent test of the proximity effect. The radiationless decay rates of the /sup 3/B/sub 1g/ state of anthracene and its derivatives have been deduced from the quantum yield of /sup 3/B/sub 1g/ .-->. /sup 3/B/sub 2u/(T/sub 1/) fluorescence and the oscillator strength of /sup 3/B/sub 1g/ .-->. /sup 3/B/sub 2u/ absorption. The results suggest that there is a hitherto unrecognized triplet state (probably a /sup 3/B/sub 3u/) slightly below the /sup 3/B/sub 1g/, which has long been thought to be the second triplet state of the molecules. Very fast /sup 3/B/sub 1g/ .-->. /sup 3/B/sub 3u/ internal conversion, over a small energy gap, is proposed to ''drive'' intersystem crossing from the /sup 1/B/sub 2u/(S/sub 1/) state to the triplet manifold via a resonance mechanism. This proposal has important bearing on the understanding of the mechanisms for singlet .-->. triplet intersystem crossing in aromatic hydrocarbons.
Author: Publisher: ISBN: Category : Aeronautics Languages : en Pages : 790
Book Description
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Author: United States. Energy Research and Development Administration. Technical Information Center Publisher: ISBN: Category : Force and energy Languages : en Pages : 1680
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Author: United States. Energy Research and Development Administration
Author: United States. Energy Research and Development Administration
Author: United States. Energy Research and Development Administration. Technical Information Center
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