Single beam zscan experiments were carried out using a 130 fs tunable Ti:Sapphire-OPA laser system. The size and the sign of the third order susceptibility were measured at 400 nm, 590 nm, 648 nm, 800 nm, and 1000 nm. At 800 measurements were conducted for different pulse durations between 130 fs and 1 ps. Our results show that the measured values of the third order nonlinearity were relatively large, negative, and strongly dependent on pulse duration and wavelength. We found that, when wavelength and pulse duration are taken into account, the third order susceptibility of Gd$-2$/ at C$-80$/ is about one order of magnitude larger than that of empty-cage C$-60$/ or C$-70$/.
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