Internal-conversion and radiative-transition processes among the 1Bu+, 1Bu− and 2Ag− states of all-trans-neurosporene as revealed by subpicosecond time-resolved Raman spectroscopy

The entire Raman spectra of the 1Bu+, 1Bu− and 2Ag− states of carotenoid were recorded, for the first time, in all-trans-neurosporene by means of subpicosecond time-resolved Raman spectroscopy using stimulated-Raman process. A sequential internal-conversion processes of 1Bu+→1Bu−→2Ag− as well as vibrational-relaxation processes in the 1Bu+ and 2Ag− states were identified by the use of a key CC stretching Raman line of each excited state. On the other hand, radiative transitions of 1Bu+→2Ag− and 1Bu−→2Ag− were identified by the accompanying 2Ag−, CC stretching Raman lines.