Internal conversion of 1Bu+ → 1Bu− → 2Ag− and fluorescence from the 1Bu− state in all-trans-neurosporene as probed by up-conversion spectroscopy

The excited-state dynamics of all-trans-neurosporene in n-hexane solution, on excitation to the 1Bu+(v=0) state, was examined by time-resolved, fluorescence up-conversion spectroscopy. The application of singular value-decomposition followed by global-fitting to a time-resolved fluorescence data matrix showed the internal conversion of 1Bu+ → 1Bu− → 2Ag− (time constants, 0.06 and 0.27 ps) and strong fluorescence from the covalent 1Bu− state. The transition dipole moment of the 1Bu− state relative to that of the 1Bu+ state was estimated to be 0.56, the value of which reflects strong mixing between these states located close-by.