Comparative Absorption Dynamics of the Singlet Excited States of Chlorophylls a and d

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Dmitry A. Cherepanov^1,2,a*, Anastasia A. Petrova², Mahir D. Mamedov², Anna I. Vishnevskaya², Fedor E. Gostev¹, Ivan V. Shelaev^1,2, Arseniy V. Aybush¹, and Victor A. Nadtochenko^1,3

¹N. N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, 119991 Moscow, Russia

²A. N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119992 Moscow, Russia

³Faculty of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia

^* To whom correspondence should be addressed.

Received March 17, 2022; Revised April 19, 2022; Accepted May 6, 2022

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Transient absorption dynamics of chlorophylls a and d dissolved in tetrahydrofuran was measured by the broadband femtosecond laser pump-probe spectroscopy in a spectral range from 400 to 870 nm. The absorption spectra of the excited S₁ singlet states of chlorophylls a and d were recorded, and the dynamics of the of the Q_y band shift of the stimulated emission (Stokes shift of fluorescence) was determined in a time range from 60 fs to 4 ps. The kinetics of the intramolecular conversion Q_x→Q_y (electronic transition S₂→S₁) was measured; the characteristic relaxation time was 54 ± 3 and 45 ± 9 fs for chlorophylls a and d, respectively.

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KEY WORDS: chlorophyll a, chlorophyll d, femtosecond laser spectroscopy, excited state spectrum, Stokes shift dynamics, internal conversion

DOI: 10.1134/S000629792210011X

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