β‐Carotene Revisited by Transient Absorption and Stimulated Raman Spectroscopy

β‐Carotene in n ‐hexane was examined by femtosecond transient absorption and stimulated Raman spectroscopy. Electronic change is separated from vibrational relaxation with the help of band integrals. Overlaid on the decay of S 1 excited‐state absorption, a picosecond process is found that is absent when the C 9 ‐methyl group is replaced by ethyl or isopropyl. It is attributed to reorganization on the S 1 potential energy surface, involving dihedral angles between C 6 and C 9 . In Raman studies, electronic states S 2 or S 1 were selected through resonance conditions. We observe a broad vibrational band at 1770 cm −1 in S 2 already. With 200 fs it decays and transforms into the well‐known S 1 Raman line for an asymmetric C=C stretching mode. Low‐frequency activity (<800 cm −1 ) in S 2 and S 1 is also seen. A dependence of solvent lines on solute dynamics implies intermolecular coupling between β‐carotene and nearby n ‐hexane molecules.