Nonlinear Optical-Response Of C-60 And C-70

Second-order hyperpolarizibilities gamma of the buckminsterfullerenes C70 at three different wavelengths were determined by third-harmonic generation in a toluene solution and compared with those of C60. Strong effects with gamma exceeding 5 x 10(-32) esu were observed in the three-photon resonant regime. The nonresonant measurements indicate a negative real hyperpolarizibility in C70 and a positive gamma for C60, both of the order of 10(-33) esu