PARENT SESSION
Posters P4Aa Chlorophyll and bilin based antenna systems. Abstracts (239-271)

-carotene in organic solvent studied by femtosecond pump-probe IR spectroscopy. Cosimo Bonetti^*,1, Luuk van Wilderen¹, Rienk van Grondelle¹, Marie Louise Groot¹, John Kennis¹, ¹ Faculty of Sciences, Amsterdam, The Netherlands

ABSTRACT- Femtosecond time-resolved pump-probe infrared spectroscopy has been used for the first time to study the excited states of carotenoids. In this work we have studied all-trans--carotene in organic solvent as a model system. -carotene has been extensively studied in the last 20 years using different forms of Raman spectroscopy; this will simplify the comparison between our result and the results already published. The sample was excited on the red edge of the absorption band by a pulse at 473 nm (8 nm fwhm, 100 nJ) and probed by a broad continuum covering the IR region of the electromagnetic spectrum between 1000-2000 cm^-1. The formation of S₂ and its decay to S₁ are clearly observed with lifetimes of 120 fs and 10 ps, respectively. In the data many features can be identified that belong to the excited state of -carotene and that can be assigned to vibrational motions of the functional units present in the Car under investigation (C-C, C=C, CH, CH₃).

KEY WORDS: Chloroform, -carotene, pump-probe, IR spectroscopy