Hot nanoplasmas from intense laser irradiation of argon clusters

Abstract

Argon ions with charge states of at least up to q = 9 are produced with 10 14 W cm −2 , 30 ps laser light pulses at 1064 nm from neutral Ar n clusters, whereas only Ar 3+ can be produced from monomers. Irradiation of cluster targets leads to ions with remarkably high kinetic energies exceeding 4.8 keV, depending on the ion charge state. The experimental results are understood in terms of cluster-sized nanoplasmas with internal electron temperatures of approximately 7 × 10 6 K which are heated by collisional electron-ion absorption. From these thermalized superdense nanoplasmas highly charged ions are ejected isotropically with the corresponding ion sound velocity. A simple Coulomb explosion model cannot account for the observed ion energies.

Simulation of the dynamics of laser-cluster interaction

“…One manifestation is the up-conversion of the incident infra-red laser into keV X-ray photons in rare-gas clusters, which takes place with a relatively high efficiency providing large X-ray yields just like in solids, yet is relatively debris-free, a property shared with gas targets [1]. Similar behavior has been observed for the emission of energetic electrons [2] or highly charged ions [3], thus making the interaction of intense short and ultra-short laser pulses with clusters a topic of considerable interest [4; 5].…”

“…One manifestation is the up-conversion of the incident infra-red laser into keV X-ray photons in rare-gas clusters, which takes place with a relatively high efficiency providing large X-ray yields just like in solids, yet is relatively debris-free, a property shared with gas targets [1]. Similar behavior has been observed for the emission of energetic electrons [2] or highly charged ions [3], thus making the interaction of intense short and ultra-short laser pulses with clusters a topic of considerable interest [4; 5].In a simple picture, the dynamics during the interaction of a strong laser pulse with a cluster can be summarized as follows [6]: the atoms of the cluster are first ionized by the incident laser pulse (inner ionization) and a cold "nano-plasma" of solid density is formed. The quasi-free electrons take part in a collective oscillation driven by the laser field and, moreover, interact with the field of the surrounding particles.…”

“…From an experimental point of view, the spectroscopy of the emitted ions [3] and electrons [2] gives information on the system a few microseconds after the femtosecond laser-pulse and the cluster disintegration. X-ray spectroscopy [16], on the other hand, presents the advantage of measurements on a much shorter time-scale, down to a few femtoseconds.…”

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

“…The experiments on laser interactions with atomic clusters have suggested that the laser-cluster interaction is more energetic than that of isolated atoms. Efficient generation of highly-charged atomic ions [1][2][3][4][5], generation of electrons and ions with MeV kinetic energies [4,[6][7][8], and emission of intense X-rays [2,9,10] were observed.…”

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

“…Experiments on clusters irradiated by the intense laser pulses have revealed efficient generation of extremely highly charged atomic ions [2][3][4][5][6][7][8] and generation of electrons and ions with MeV kinetic energies [6,7,[9][10][11]. Several other theoretical models have been proposed to explain the mechanism underlying the production of highly charged energetic ions in interaction of atomic clusters with intense laser pulses.…”