Sub-10 fs time resolved study of excited state relaxation in all-trans-beta-carotene

The ultrafast internal conversion S-2 --> S-1 following photoexcitation in all-trans-beta -carotene is studied with unprecedented time resolution. Sub -10 fs optical pulses are used to excite and probe the optical dynamics of the molecule dissolved in solution. We observed the ultrafast decay of the stimulated emission from S-2 and formation of the absorption band assigned to S-1 --> S-n transitions within 500 fs. Periodic oscillations of the ampl itude are superimposed to the transient transmission difference and assigne d to ground state nuclear wavepacket motion excited via impulsive Raman sca ttering. (C) 2001 Elsevier Science B.V. All rights reserved.