Nonlinear optical response of the higher fullerene C90- a comparison with C60

Degenerate four-wave-mixing measurements on C90 in CS2 with different concentrations were performed using 70 ps laser pulses at 0.532 μm. The dependence of the conjugate signal intensity on the incident laser power and the concentration of C90 were investigated. By optimizing experimental parameters, the second hyperpolarizability γ1111 of C90 was determined to be (1.8 ± 0.6) × 10−30 esu, which is approximately eight times that of the C60 molecule measured under identical conditions. Our results are in accord with the theoretical prediction that higher fullerenes should show larger nonlinear optical responses.