Oscillations and electron emission from laser produced cluster nanoplasma

Summary form only given. The nanoplasma produced by laser pulses of moderate intensities 10¹³-10¹⁶ W/cm² targeted at metal clusters is studied by molecular dynamics (MD) simulations. Whereas a lot of the cluster plasma studies are concerned with the Coulomb explosion of the ion core we focus on the electron dynamics just after cluster ionization. In particular we consider electron eigenmodes and electron emission depending on the cluster size and plasma temperature. One of the distinguishing features of the cluster plasma is the violation of the plasma neutrality. Due to the laser ionization and further thermionic emission from the plasma surface the cluster gains an uncompensated positive charge. With respect to a small number of particles in the clusters under consideration 10-10⁶ this charge determines the rate of plasma e,pansions, affects the rate of ionization-recombination processes, electron density profile, and optical properties of the cluster plasma. In this work we propose a model of thermionic emission of nanoclusters based on our MD simulation results. This model qualitatively e,plains known experimental results and it is in a good agreement with other simulations. The dependency of the electron oscillation spectrum on the cluster charge is discussed. The frequencies and damping rates of different electron eigenmodes including Mie and Langmuir oscillations are obtained.