Recollision-induced plasmon excitation in strong laser fields

Recolliding electrons are responsible for many of the interesting phenomena observed in the interaction of strong laser fields with atoms and molecules. We show that in multielectron targets such as C-60 an important recollision pathway opens up: the returning electron may excite collective modes even if the laser frequency is far off-resonant. We formulate a simple analytical theory which predicts that the recollision-induced excitation of collective modes should dominate over the usual harmonic generation yield at 800 nm wavelength. In this case the tomographic imaging of complex multielectron systems may be obscured. We employ a time-dependent density functional model of C-60 and show that with increasing laser wavelength the dynamics becomes more and more single-active-electron-like, suggesting that long wavelengths are to be preferred for imaging purposes.