WAVELENGTH DEPENDENCE OF THE NONLINEAR ABSORPTION OF C-60-TOLUENE ANDC-70-TOLUENE SOLUTIONS

The nonlinear transmission properties of C-60 and C-70 in toluene solu tion in the ultraviolet and visible spectral regions have been studied using nanosecond laser pulses. Whereas at 308 and 534 nm both fullere nes behave as reverse saturable absorbers, at 337 nm their behavior ch anges to that of a saturable absorber. A five-level rate equation mode l was developed that reproduces adequately the dependence of transmitt ance with intensity at the different irradiation wavelengths and allow s us to estimate the absorption cross sections of the first excited si nglet state for each fullerene.