Dynamics of vibrational relaxation in the S1 state of carotenoids having 11 conjugated CC bonds

Transient absorption spectra and kinetics in the 470–650 nm region were recorded for lycopene, β-carotene and zeaxanthin, all carotenoids with 11 conjugated double bonds, in two solvents with different polarity. Analysis of the red wing of the carotenoid S1–Sn transition revealed presence of a pronounced shoulder at early delay times. The kinetics recorded at this low-energy shoulder of the S1–Sn transition yields an additional decay component of 500–800 fs in addition to the main S1 decay. This dynamics is ascribed to a vibrational relaxation in the S1 state of the carotenoids.