Frequencies, times, and forces in the dynamics of Na clusters

Abstract.

Laser excitation of metal clusters depends on various parameters such as frequency, intensity, and pulse time. We give here an overview of relevant time scales and forces for the example of Na clusters. Variation of laser intensity is studied in connection with second harmonic generation. We see a rather sudden transition from a perturbative regime at low intensities to a field-dominated regime for larger intensities. We use the non-linearized time-dependent local density approximation (TDLDA), together with a local pseudopotential for the interaction of the valence electrons with the ions. Explicit ionic motion is taken into account in one test case where we demonstrate the importance of ionic effects for the detailed time evolution at times larger than 100 fs.