C₆₀ in intense femtosecond laser pulses: Nonlinear dipole response and ionization

We study the interaction of strong femtosecond laser pulses with the C₆₀ molecule employing time-dependent density-functional theory with the ionic background treated in a jellium approximation. The laser intensities considered are below the threshold of strong fragmentation but too high for perturbative treatments such as linear response. The nonlinear response of the model to excitations by short pulses of frequencies up to 45 eV is presented and analyzed with the help of Kohn-Sham orbital resolved dipole spectra. In femtosecond laser pulses of 800 nm wavelength ionization is found to occur multiphotonlike rather than via excitation of a “giant” resonance.