FIGURE 1.
Scheme of the electronic and vibrational levels of carotenoids and bacterio-chlorophylls used in the model. Population dynamics are indicated with dashed arrows, ΔT/T signals with solid arrows. After photoexcitation from the carotenoid S0 ground state to the S2 state, internal conversion occurs to the S1 state (with kIC21 rate constant), where vibrational relaxation is modeled as energy cascade within three consecutive vibrational levels (with kV2 and kV1 rate constants). Relaxation back to the ground state then takes place with kIC10 rate constant. When the carotenoid is in the LH2 complex, energy transfer can occur from the S2 state to the bacterio-chlorophyll Qx with kET2 rate constant or from the carotenoid S1 state to the bacterio-chlorophyll Qy with kET1 rate constant.