WAVE-DISPERSED 2-PHOTON ABSORPTION OF C-60

We report the two-photon absorption (TPA) spectrum of C-60 in the wave length range lambda=0.7-1.5 mu m. The TPA coefficient beta of the poly crystalline film shows a broad peak, with beta approximate to 25 cm/GW , around 0.95 mu m and drops below 3 cm/GW at lambda > 1.2 mu m. We fi nd that the nonlinear absorption, and also the sign of the nonlinear r efraction above and below the TPA maximum, are satisfactorily accounte d for by modeling the response with a two-photon state positioned at 2 .58 eV. [S0163-1829(97)50940-4].