The dynamics and origin of the unrelaxed fluorescence of free-base tetraphenylporphyrin

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• 作者：Bart艂omiej Bia艂kowski^a ; Yuriy Stepanenko^a ; Micha艂 Nejbauer^a ; Czes艂aw Radzewicz^a ; ^b ; ^{Czeslaw.Radzewicz@fuw.edu.pl} ; Jacek Waluk^a ; ^c ; ^{waluk@ichf.edu.pl}
• 关键词：Tetraphenylporphyrin ; Excited-state dynamics ; Femtosecond spectroscopy ; Fluorescence up-conversion
• 刊名：Journal of Photochemistry and Photobiology A ; Chemistry
• 出版年：2012
• 期刊代码：66_10106030
• 类别：ch
• 出版时间：15 April, 2012
• 卷：234
• 期：Complete
• 页码：100-106
• 文件大小：700 K

摘要

Femtosecond studies of fluorescence of free-base tetraphenylporphyrin in solution were carried out using a homebuilt spectrometer which allows tracing the temporal evolution of the entire emission spectrum with the resolution of 150 fs, as well as the measurement of time-resolved fluorescence anisotropy. The S₁-S₀ (Q_x) fluorescence was found to appear immediately after excitation, independent of the excitation wavelength. In addition, a shorter wavelength fluorescence was observed, decaying on a picosecond time scale. It was assigned to the population of the S₂ (Q_y) state. A model which can explain both the very fast rise of S₁ emission and the picosecond decay of S₂ was proposed: it assumes a reversible internal conversion between S₂ and S₁ states, modulated by relaxation from the higher vibronic levels of the latter.