The dynamics of the S1 excited states of carotenoids

✍ Scribed by Harry A. Frank; Roya Farhoosh; Ronald Gebhard; Johan Lugtenburg; David Gosztola; Michael R. Wasielewski

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 444 KB
• Volume: 207
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(93)85016-h

✦ Synopsis

Transient absorption spectroscopy was used to measure the Sr dynamics of four all-trans-carotenoids: 3,4,7,8_tetrahydrospheroidene, 3,4,5,6-tetrahydrospheroidene, 3,4_dihydrospheroidene and spheroidene. After excitation into the S2 state and subsequent relaxation to the Sr state, the S ,-+Sn electronic absorption bands in the region 460-520 nm were probed and observed to decay with single-exponential kinetics: r=407+ 23 ps for 3,4,7,&tetrahydrospheroidene, 85? 5 ps for 3,4,5,6_tetrahydrospheroidene, 25.4 +_ 0.9 ps for 3,4_dihydrospheroidene and 8.7 t 0. I ps for spheroidene. These data are discussed in three contexts: ( 1) as a test of the adherence of carotenoids to the energy gap law; (2) as a means of determining the S, state energy of spheroidene, which appears to be at 14100 cm-r; and (3) in terms of the constraints placed on the efficiencies of carotenoid-to-chlorophyll energy transfer in photosynthetic systems.