Time-resolved optical Kerr response ofC84inCS2

The large optical response of ${\mathrm{C}}_{84}$ is demonstrated by means of the optical Kerr effect. Using 150-fs laser pulses with a wavelength of 647 nm, we got a transient response that was primarily pulse limited. By comparing nonlinear responses with that of the ${\mathrm{CS}}_2$ reference, we acquired large second-order hyperpolarizability for ${\mathrm{C}}_{84}$ and ${\mathrm{C}}_{70}$ with ${\gamma }_{1111}$ of 5.2×${10}^{\mathrm{-}31}$ and 4.7×${10}^{\mathrm{-}31}$ esu, respectively. The different optical responses of ${\mathrm{C}}_{84}$ and ${\mathrm{C}}_{70}$ were interpreted using a pure-π-conjugated-electrons model and the influence of ground-state structures of ${\mathrm{C}}_{84}$ isomers. Our results further confirmed the postulated ${\mathit{D}}_2$(22) and ${\mathit{D}}_{2\mathit{d}}$(23) structures as the ground-state structure of ${\mathrm{C}}_{84}$.