Calculations on the spectra and nonlinear third‐order optical susceptibility of c70

The equilibrium geometry and UV‐visible spectra of C70 were examined using semiempirical INDO/2 and INDO/CI methods. The results obtained are in good accord with experimental results. On the basis of correct electronic spectra, calculations of the nonlinear third‐order optical susceptibility (γijkl) of C70 were performed using the INDO/SDCI method combined with a sum‐over‐states expression. The calculated value for <γ> (‐2 ω, ω, ω, O) is 0.882 × 10−33 esu (ω = 1.91 μm), which is in good agreement with observation.