Excited-state dynamics among the 1B+u, 1B-u and 2A-g 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 1B(u)(+) state and (b) transient absorption from the 1B(u)(-) state were identified as major components. In carbon disulfide, (c) transient absorption from the 2A(g)(-) state was clearly identified as an additional component. The results have confirmed the sequential internal conversion processes of 1B(u)(+) --> 1B(u)(-) --> 2A(g)(-). (C) 2000 Elsevier Science B.V. All rights reserved.