Nonlinear optical response of the higher fullerene C-90 - A comparison with C-60

Degenerate four-wave-mixing measurements on C-90 in CS2 with different concentrations were performed using 70 ps laser pulses at 0.532 mu m. The dependence of the conjugate signal intensity on the incident laser power and the concentration of C-90 were investigated, By optimizing experimental parameters, the second hyperpolarizability gamma(1111) of C-90 was determined to be (1.8 +/- 0.6) X 10(-30) esu, which is approximately eight times that of the C-60 molecule measured under identical conditions. Our results are in accord with the theoretical prediction that higher fullerenes should show larger nonlinear optical responses. (C) 1997 Elsevier Science B.V.