Time-resolved degenerate four-wave mixing experiments were conducted on films of pure Qo using a 35 ps Nd:YAG laser. The measurements wavelength 1.064 μm was far off resonance with any one-photon absorption bands. A small linear absorption coefficient α=6 cm−1 was measured at this wavelength. The third-order optical susceptibility χxxxx
(3) of C60, derived from its phase conjugate signal, is 7 × 10−12 esu. The nonlinear optical temporal response was largely laser-pulse limited. Evidence for a fifth-order contribution to the nonlinear optical response was observed at high laser intensities.