Excited-state dynamics of the 1Bu+,3Ag−, and 1Bu− states in a carotenoid molecule by 5-fs absorption spectroscopy

The time-resolved absorption spectra of all-trans-spirilloxanthin were recorded by the use of extremely stable sub-5-fs pulses covering coherently the main visible range of 520-700 nm. All the theoretically predicted and long-lasting argued states (1Bu+, 3Ag-, and 1Bu- states) were clearly identified for the first time. The spectrum of each component and lifetime were determined without ambiguity by the global fitting method. Their lifetimes were in sequence ∼10, 25±2, and 140±30 fs.