Real time nuclear dynamics of S/sub 2/-S/sub 1/ internal conversion in all-trans-/spl beta/-carotene

Summary form only given. Carotenoids are a widespread class of natural pigment, that can photosynthesis absorbed light in the blue-green region and transfer energy to the (bacterio)chlorophylls. The low lying electronic structure of carotenoids has an optically bright excited state (S/sub 2/), that can be reached by dipole allowed transitions from the ground state (S/sub 0/), and a dark state, at slightly lower energy (S/sub 1/). In this work we report on coherent nuclear motion accompanying internal conversion in all-trans-p-carotene in solution, studied by pump-probe spectroscopy with 5 fs optical pulses. The excitation source was an optical parametric amplifier (OPA) based on noncollinear phase matching in /spl beta/-barium borate followed by pulse compression based on chirped mirrors.