We report the nonlinear optical properties of one metal cluster [PPh4][(CpWS3)-W-*(CuBr)(3)(dppm)] by picosecond and nanosecond laser pulses. The third-order nonlinear susceptibility X(3) is measured by degenerate four-wave mixing, the nonlinear absorption by the Z-scan technique, and optical limiting response by the transmission technique. The experimental data are theoretically fitted, and the mechanism for the third-order optical nonlinearities and the optical limiting properties are discussed, and the absorption cross sections of the ground state and the excited state are evaluated by a rate equation model. (C) 2003 Elsevier Science B.V. All rights reserved.