Absorption and decay of excited states of azomethine dyes on picosecond timescales
1990; Elsevier BV; Volume: 174; Issue: 5 Linguagem: Inglês
10.1016/s0009-2614(90)87172-n
ISSN1873-4448
AutoresF. Wilkinson, David R. Worrall, R. S. Chittock,
Tópico(s)Electrochemical Analysis and Applications
ResumoAbstract The process leading to the very rapid relaxation of excited states of pyrazolotriazole azomethine dyes have been studied using picosecond absorption spectroscopy. We report the first observation of transient absorption changes in these dyes on this timescale, the rise and decay of which can be globally fitted using the sum of two exponential terms with lifetimes τ 1 = 3 ps and τ 2 = 9 ps for traces recorded in di- n -butylphthalate solution, and τ 1 = 2 ps and τ 2 = 5 ps in methanol solution. We present a model involving “intended” crossings of S 1 and S 0 states occurring at some early stage along the isomerisation coordinate before the configuration of the activated complex for ground-state isomerisation is reached to account for the rapid efficient internal conversion observed together with the low measured yield for photoisomerisation.
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