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

The ultrafast internal conversion S2→S1 following photoexcitation in all-trans-β-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 S2 and formation of the absorption band assigned to S1→Sn transitions within 500 fs. Periodic oscillations of the amplitude are superimposed to the transient transmission difference and assigned to ground state nuclear wavepacket motion excited via impulsive Raman scattering.