Dynamics of Argon Clusters in an Intense Laser Pulse: Bloch-Like Hydrodynamic Model

Abstract

The dynamics of small (≤ 55 atoms) argon clusters ionized by an intense, infrared, femtosecond laser pulse is studied using a Bloch-like hydrodynamic model. Evolution of both free electrons and ions formed in the cluster explosion process is examined. Oscillations of the electron cloud in a rare-gas atomic cluster are described as a motion of a fluid obeying Bloch-like hydrodynamic equations. Our theoretical approach includes all possible ionization mechanisms: tunnel (or field) ionization both by an external laser field, and by an internal field due to the space-charge distribution inside the cluster, as well as electron-impact (or collisional) ionization. The results of our simulations are compared both with experimental findings and with predictions of other theoretical models.

Free Electrons Generation in the Interaction of Intense Laser Pulses with Atomic Clusters

“…In this paper we further extend the theoretical results obtained in our previous papers [13,15] and investigate the kinetic energy distribution of the free electrons generated in the process of laser interaction with rare-gas atomic clusters. A time-dependent Thomas-Fermi model allows us to study both the infrared and short-wavelength frequency cases in the same unified way.…”

“…The short-wavelength photons with energy sufficient to ionize isolated xenon and almost sufficient to ionize argon atoms were generated by a free-electron laser. The cluster explosion and ionization mechanisms in this frequency regime [11][12][13] turn out to be very different from that known from the infrared and optical pulses [14,15].…”

“…We assume that the oscillations of the electron cloud in a rare-gas atomic cluster can be viewed as a motion of a fluid characterized by a density, and a velocity field obeying the standard conservation equations for number of particles and momentum [14,15]. These hydrodynamic equations for the electron density ρ should be supplemented by the Newton equations of motion for the positions of the nuclei [14,15].…”

“…These hydrodynamic equations for the electron density ρ should be supplemented by the Newton equations of motion for the positions of the nuclei [14,15]. The interaction with the laser pulse is treated within the dipole approximation [14,15].…”

“…These hydrodynamic equations for the electron density ρ should be supplemented by the Newton equations of motion for the positions of the nuclei [14,15]. The interaction with the laser pulse is treated within the dipole approximation [14,15]. The linearly polarized wave of a pulse used in the simulations is assumed to have a field envelope proportional to sine squared [14,15].…”