Abstract
In order to understand the important functions of carotenoids in photosynthesis systems, their excited-state energies and lifetimes should be determined correctly. Because the time-resolved fluorescence up-conversion spectroscopy is free from stimulated emission and transient absorption, it is very suitable to achieve that. For the sake of obtaining the up-conversion signal of the 1Bu+(0)→1Ag-(0) transition and minimize the effect of vibrational relaxation, spheroidene was excited upon the 1Bu+(1)←1Ag-(0) transition. We have recently succeeded in obtaining time-resolved fluorescence data by the use of 1 KHz, 100 fs pulses. SVD followed by global fitting was used to analysis the time-resolved fluorescence up-conversion spectra, we found that two dynamic processes were present in the spectra. We assigned the faster and slower processes to the relaxation dynamics of 1Bu+ and 1Bu- states, respectively. The lifetimes of 1Bu+ and 1Bu- states were determined to be 0.04 ps and 0.30 ps, respectively.
