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

Dy@C82 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@C82 were performed using 70 ps laser pulses at 0.532 μm. The magnitude of the second hyperpolarizability γ1111 of the Dy@C82 molecule was (3.0±0.5)×10−30 esu at 0.532 μm. The resonant enhancement and the electron transfer from the trapped dysprosium to the C82 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.