Direct measurement of S2 -- S0 fluorescence lifetimes and anisotropy of tetraphenylporphyrins

Gagik G. Gurzadyan; Thu-Hoa Tran-Thi; Thomas Gustavsson

doi:10.1117/12.375279

28 December 1999 Direct measurement of S₂ -- S₀ fluorescence lifetimes and anisotropy of tetraphenylporphyrins

Gagik G. Gurzadyan, Thu-Hoa Tran-Thi, Thomas Gustavsson

Proceedings Volume 4060, New Trends in Atomic and Molecular Spectroscopy; (1999) https://doi.org/10.1117/12.375279
Event: New Trends in Atomic and Molecular Spectroscopy, 1999, none, Russian Federation

Abstract

Various tetraphenylporphyrins (zinc, magnesium, free base) were excited to the upper electronic levels of the Soret band with the second harmonic of a mode-locked Ti-sapphire laser (394 nm). An up-conversion fluorescence set-up with the time resolution of 120 fs was used to measure the decay times of the S₂ fluorescence in conjunction with the risetime of the S₁ fluorescence. The depopulation of the excited electronic state S₂ was studied as a function of the metal ion and the solvent. The lifetimes of the electronic S₂ level, measured for ZnTPP and MgTPP in different solvents were (tau) equals 1.4 - 3.4 ps. The depopulation channel from S₂ to S₁ was studied by measuring simultaneously the decay of S₂ and the rise of S₁ fluorescence. The rate constant of the process can be correlated to the energy gap between the S₂ and S₁ levels, which depends on the nature of the metal ions and solvents. The rotational dynamics in the Soret band was also studied by measuring the anisotropy of S₂ ---> S₀ fluorescence. The anisotropy decay of S₂ fluorescence was found to be biexponential, with a fast component around 100 fs and a slow one (t >> 10 ps), attributed to the partial dephasing of the degenerate energy levels of the S₂ state and to rotational diffusion, respectively.

Citation Download Citation

Gagik G. Gurzadyan, Thu-Hoa Tran-Thi, and Thomas Gustavsson "Direct measurement of S₂ -- S₀ fluorescence lifetimes and anisotropy of tetraphenylporphyrins", Proc. SPIE 4060, New Trends in Atomic and Molecular Spectroscopy, (28 December 1999); https://doi.org/10.1117/12.375279

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