Near-infrared time-resolved study of the S-1 state dynamics of the carotenoid spheroidene

Summary, in English

Using a novel experimental approach based on near-infrared femtosecond absorption spectroscopy, we have determined the energy of the S-1 state of the carotenoid spheroidene. The energy of this state is 13 400 +/- 90 cm(-1) at both 293 and 186 K, showing that there is no temperature-induced shift of the S-1 level. A discrepancy of about 800 cm(-1) between the S-1 energy determined here and that obtained from previous fluorescence and resonance Raman measurements is explained in terms of the different conformational species coexisting in the S-1 excited state. Measurements of kinetics in the near-infrared region revealed that at least three relaxation processes take place after excitation of spheroidene into its S-2 state. Ultrafast S-2 --> S-1 internal conversion occurs within the first 300 fs, followed by vibrational cooling in the SI state, which occurs on a time scale of similar to 700 fs. The S-1 lifetime is 8 ps at 293 K, in good agreement with previous measurements of the S-1 --> S-N transition. A somewhat longer S-1 lifetime of 9.5 ps is observed at 186 K.

• Author: Tornáš Polívka; Donatas Zigmantas; Harry A. Frank; James A. Bautista; Jennifer L. Herek; Yasushi Koyama; Ritsuko Fujii; Villy Sundström
• Department/s: Chemical Physics
• Publishing year: 2001-02-08
• Language: English
• Pages: 1072-1080
• Publication/Series: The Journal of Physical Chemistry Part B
• Volume: 105
• Issue: 5
• Links: http://dx.doi.org/10.1021/jp002206s
• Document type: Journal article
• Publisher: The American Chemical Society (ACS)
• Topic: Physical Chemistry (including Surface- and Colloid Chemistry)
• Keywords: long polyenes; crystal-structure; different extents; 2-photon fluorescence excitation; light-harvesting complex; rhodobacter-sphaeroides r-26.1; pi-electron conjugation; all-trans-spheroidene; xanthophyll cycle; energy-transfer
• Status: Published
• ISBN/ISSN/Other: ISSN: 1520-5207