The third-order non-linear optical response of the endohedral metallofullerene Dy@C82

Dy@C-82 has been prepared by an efficient solvent extraction procedure and characterized by negative-ion desorption chemical ionization mass spectrometry and UV-VIS-near-IR absorption. Degenerate four-wave-mixing measurements on the CS2 solution of Dy@C-82 were performed using 70 ps laser pulses at 0.532 mu m. The magnitude of the second hyperpolarizability gamma(1111) of the Dy@C-82 molecule was (3.0 +/- 0.5)x 10(-30) esu at 0.532 mu m. The resonant enhancement and the electron transfer from the trapped dysprosium to the C,, cage are suggested to bring about its larger non-linear optical response relative to the empty fullerene. The experimental results are in good agreement with our calculations based on an extended Su-Schrieffer-Heeger model and the sum-over-state method. (C) 1998 Elsevier Science B.V. All rights reserved.