The very early events following photoexcitation of carotenoids.
The recent availability of laser pulses with 10-20 fs duration, tunable throughout the visible and near infrared wavelengths, has facilitated the investigation, with unprecedented temporal resolution, into the very early events of energy relaxation in carotenoids [Science 298 (2002) 2395; Synth. Metals 139 (2003) 893]. This has enabled us to clearly demonstrate the existence of an additional intermediate state, Sx, lying between the S2 (1(1)Bu+) and S1 (2(1)Ag-) states. In addition, by applying time-resolved stimulated Raman spectroscopy with femtosecond time resolution, it has also been shown that vibrational relaxation in electronic excited states plays an important role in these interconversions. In this mini-review, we describe briefly the current understanding of Sx and the other intermediate excited states that can be formed by relaxation from S2, mainly focusing attention on the above two topics. Emphasis is also placed on some of the major remaining unsolved issues in carotenoid photochemistry.
Light and Control, PRESTO/JST and Department of Physics, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan. hassy@sci.osaka-cu.ac.jp
Hideki
H
Hashimoto
Kazuhiro
K
Yanagi
Masayuki
M
Yoshizawa
Dario
D
Polli
Giulio
G
Cerullo
Guglielmo
G
Lanzani
Sandro
S
De Silvestri
Alastair T
AT
Gardiner
Richard J
RJ
Cogdell
D002338:Carotenoids / Q000737:chemistry*; D007259:Infrared Rays; D007700:Kinetics; D008027:Light; D010777:Photochemistry; D026082:Singlet Oxygen; D013053:Spectrophotometry / Q000379:methods; D013816:Thermodynamics
D026082:Singlet Oxygen; D002338:Carotenoids