Electron dynamics in Na₄ clusters under femtosecond laser irradiation

The electron dynamics in metal clusters under femtosecond laser irradiation yield excited nonlinear phenomena under the control of laser parameters. In this study, metal clusters Na₄ as an example under femtosecond laser irradiation have been observed within the framework of time-dependent density functional theory molecular dynamics (TDDFT-MD), which self-consistently couples a quantum-mechanical TDDFT treatment of valence electrons with a classical molecular dynamics description of ionic cores. The specific excitation frequencies and polarization directions of the laser have been chosen to investigate the behavior of the dipole response and ionization process. We found that it is necessary to explore the electron dynamics of metal clusters by matching the laser frequency and polarization direction. In addition, resonant dipole oscillations induced by suitable laser parameters show pronounced enhancement of the ionization behavior.