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. © 1994 John Wiley & Sons, Inc.