Excited-state dynamics among the 1Bu+, 1Bu− and 2Ag− states of all-trans-neurosporene as revealed by near-infrared time-resolved absorption spectroscopy

Subpicosecond time-resolved absorption spectra in the 840–1040 nm region were recorded for all-trans-neurosporene in nonpolar solvents having different polarizabilities, and analyzed by means of singular-value decomposition (SVD) and subsequent global fitting using sequential models. In n-hexane, n-pentadecane and benzene, (a) transient absorption and stimulated emission from the 1Bu+ state and (b) transient absorption from the 1Bu− state were identified as major components. In carbon disulfide, (c) transient absorption from the 2Ag− state was clearly identified as an additional component. The results have confirmed the sequential internal conversion processes of 1Bu+ → 1Bu− → 2Ag−.