Nonlinear electron dynamics in metal clusters

Recent experimental developments give more and more access to cluster excit ations beyond the regime of linear response. Most theoretical descriptions of the induced nonlinear electron dynamics are based on the time-dependent local density approximation (TDLDA) and related schemes. We review the pres ent status of TDLDA calculations for metal clusters, considering formal asp ects of the theory, recipes for its numerical implementation as well as a v ariety of applications. These applications are presented by first summarizi ng basic linear spectral properties of the systems under study and then int roducing two mechanisms for strong excitations: collision with highly charg ed and fast ions, and irradiation with strong femtosecond laser pulses. We present results for observables that are relevant for experiments, includin g ionization, energy balance, second-harmonic generation, electron emission spectra and, last but not least, we discuss the effects of ionic motion du ring the electronic dynamics. On the theoretical side, we also discuss semi classical approaches and extensions beyond TDLDA, such as self-interaction corrections and the influence of electron-electron collisions. (C) 2000 Els evier Science B.V. All rights reserved.