Theoretical study of vibrational relaxation and internal conversion dynamics of chlorophyll-a in ethyl acetate solvent in femtosecond laser fields

The density matrix and the transient linear susceptibility theories are used to calculate the fluorescence depletion spectrum and the internal conversion (IC) time of chlorophyll-a (Chl-a) in ethyl acetate solvent. The IC time and the vibrational relaxation time of Chl-a in the ethyl acetate solvent are 133 fs and 1.5 ps at room temperature, respectively. The calculated fluorescence depletion spectrum of Chl-a in the ethyl acetate solvent agrees well with the experimental result of Shi et al. [Shi et al.,Chem. Phys. Lett. 410 (2005) 260]. The effects of solvation and the IC time on the fluorescence depletion spectrum are also discussed.