COLLECTIVE CHARGE-DENSITY FLUCTUATIONS AND NONLINEAR-OPTICAL RESPONSEOF C-60

The absolute magnitude of the optical susceptibility X((3)), for C-60 and its frequency dispersion are calculated using the Pariser-Parr-Pop le (PPP) model by deriving equations of motion for the single electron density matrix and solving them using the time-dependent Hartree-Fock procedure. Collective charge density fluctuations induced by the radi ation fields are shown to provide the mechanism for the linear and the nonlinear optical response. The insight provided by the present real space picture allows the direct comparison with linear conjugated poly enes.