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An ultrafast time‐resolved anisotropy study of bacteriochlorophyll a in pyridine
Author(s) -
Martinsson Peter,
Sundström Villy,
Åkesson Eva
Publication year - 2000
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)01725-1
Subject(s) - anisotropy , picosecond , femtosecond , excited state , ultrafast laser spectroscopy , absorption (acoustics) , wavelength , chemistry , molecular physics , materials science , optics , atomic physics , optoelectronics , physics , laser
The transient absorption anisotropy spectrum of bacteriochlorophyll a (BChl a ) in pyridine was measured in the wavelength interval 550–850 nm, 1 ps after optical excitation with a 792‐nm femtosecond light pulse. In the wavelength region of Q y absorption and stimulated emission (775–825 nm), the anisotropy was found to be close to the theoretically expected value (0.4) for a two‐level system. In the wavelength region 650–750 nm, where the transient absorption signal is dominated by excited state absorption, the anisotropy is reduced to ∼0.18. Anisotropy kinetics were measured at several wavelengths and found to be constant within the time window 0–5 ps, showing that no internal dynamics of the BChl a molecule change the anisotropy on the time scale of tens of picoseconds.