Nanosecond reverse saturable absorption in metal cluster cis-Cp*2Mo2S4Cu2I2•(CH2Cl2)2 solution

Nonlinear absorptive property of a novel metal cluster cis-Cp*2Mo2S4Cu2I2 center dot(CH2Cl2)(2) in CH2Cl2 solution is studied by using an open-aperture Z-scan technique with laser pulse of 8ns pulse-width at the wavelength of 532nm. The experimental results shows that the cluster has strong nonlinear absorption under the 8ns pulse excitation. A picosecond time resolved pump-probe experiments at 532nm has been used to study the nonlinear origin of the cluster. The pump-probe response of the metal cluster is similar to that Of C-60 solution, which implies that the nonlinear mechanisms are the same of the two materials. By establishing a five-level model for the cluster, several nonlinear optical parameters, such as the relaxation time of the excited singlet state, the absorption cross sections of the excited state of the cluster are obtained. According to the results of the experiments and numerical simulations, a conclusion can be obtained that, at 532nm, the effective absorption of the triplet state of the cluster solution is the dominant mechanism causing the reverse saturable absorption. The theoretical results are in good agreement with the experimental data, which not only shows the availability of the kinetic model but also demonstrates the close relationship between the nonlinear absorptive property of the cluster and its dynamic processes.