Frequencies of the Franck-Condon active ag CC stretching mode in the 2 1A−g excited state of carotenoids

✍ Scribed by T. Noguchi; H. Hayashi; M. Tasumi; G.H. Atkinson

• Publisher: Elsevier Science
• Year: 1990
• Tongue: English
• Weight: 624 KB
• Volume: 175
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(90)85536-l

✦ Synopsis

Picosecond time-resolved resonance Raman spectra (C=C stretching region) of the 2 '& excited state (S, ) have been measured for B-carotene, three derivatives of B-carotene (f%-apoX-carotenal, ethyl &apo-8'-carotenoate and canthaxanthin), and five carotenoids extracted from photosynthetic bacteria (neurosporene, spheroidene, spheroidenone, rhodopin and spirilloxanthin). In all of these carotenoids, the frequency of the Franck-Condon active a, C=C stretching mode in S, is much larger than that found in the iA; ground state (S,). The frequencies in both So and S, correlate well with the absorption maxima for all carotenoids examined except B-apo-l'-carotenal and ethyl B-apo-8'-carotenoate, in which cases the S, frequencies are smaller than expected. These results are discussed with respect to the previous studies of the shorter polyenes and a vibronic coupling mechanism.