Observation of Two-Photon Induced Excited-State Absorption Phenomena in C60 and C70 Derivatives

Four fullerene dyads with different cabazole units, named a, b, c, d, were studied by using a femtosecond laser with 780nm wavelength using Z-scan methods. Interestingly, all of them show strong two-photon induced excitedstate absorption behaviors, which were observed firstly in femtosecond timescale. The values of their excited-state absorption cross-section were up to 6.07 × 10？18, 7.27 × 10？18, 3.86 × 10？18 and 4.51 × 10？18 cm？1 for a, b, c, and d, respectively