Conjugation length dependence of relaxation kinetics in β-carotene homologs probed by femtosecond Kerr-gate fluorescence spectroscopy

Ultrafast dynamics of the S2 state in all-trans-carotenoids has been investigated eliminating effect of excess vibrational energy. The relaxation rate of the S2 state has a minimum at a number of conjugated double bonds n = 9 and shows anomalous dependence on the energy gap between the S2 and S1 states.