Ground state recovery rate

The same authors also investigated the bleaching and recovery of the ground state of the dye after a 1-ps laser excitation [48]. Since these experiments were performed under open-circuit conditions, all the electrons transferred from the excited dye into the conduction band of SnS2, had to return to the oxidized dye. The corresponding ground state recovery was found to occur within about 10 ps. Other investigations on transfer rates will be discussed in Section 10.2.7. 

It should be mentioned that direct recombination from the excited molecule to the ground state, and also the ground state recovery due to recombination and transfer of electrons via surface states (compare with Fig. 10.21), have been neglected in this derivation. According to Eq. (10.17), the exponential decay is determined by k. Since in heavily doped electrodes, ki includes the tunneling rate constant kj, the decay should... 

In the case of vibrational responses the population relaxation times may be dominating the coherence decays. In addition, it can be essential to incorporate the multilevel nature of molecular vibrators into the response. The rate of repopulation of the ground state is seldom equal to the decay of the fundamental V = 1 state, so there can be bottlenecks in the ground state recovery. Following... 

Efficient operation of these cells requires, inter alia, that the M(III) species (obtained by electron injection) be reduced by 1 in solution preferentially to recombination with the electrons that were injected into the Ti02.To probe this competition, both recombination rates and iodide oxidation rates were determined. Recombination rates were investigated by monitoring the recovery of the characteristic ground-state M(II) MLCT bands in the visible region. These recovery rates were found to obey a rate law having two second-order terms, as in Eq. (22). 

It is of interest to note that the 225-ps bleach recovery transient observed in the transient absorption kinetics is significantly shorter than the 275-ps decays observed in the polarized emission and the bare nanoparticle absorption kinetics. Tltis difference, along with magnitude of this component at 660 and 700 nm, indicates that partial repopulation of the ground-state dye from the conduction-band electron occurs with this time constant. These dynamics are summarized in Scheme 1. From the difference of the bare nanoparticle and nanoparticle/dye conduction-band decays, it is possible to estimate the rates of conduction-band reverse electron transfer. These values (275 ps and 225 ps, respectively) give an estimate for the reverse electron-transfer time of about 1.2 ns. The ratio of the... 

Figure 5. Schematics of the Picosecond Flash Kinetic Set Up for Measurement of Ground State Bleaching Recovery Rates.

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