Communication: Ionization and Coulomb explosion of xenon clusters by intense, few-cycle laser pulses

Abstract

Intense, ultrashort pulses of 800 nm laser light (12 fs, ∼4 optical cycles) of peak intensity 5×10 14 W cm −2 have been used to irradiate gas-phase Xe n clusters (n=500-25,000) so as to induce multiple ionization and subsequent Coulomb explosion. Energy distributions of exploding ions are measured in the few-cycle domain that does not allow sufficient time for the cluster to undergo Coulombdriven expansion. This results in overall dynamics that appear to be significantly different to those in the many-cycle regime. One manifestation is that the maximum ion energies are measured to be much lower than those obtained when longer pulses of the same intensity are used. Ion yields are cluster-size independent but polarization dependent in that they are significantly larger when the polarization is perpendicular to the detection axis than along it. This unexpected behavior is qualitatively rationalized in terms of a spatially anisotropic shielding effect induced by the electronic charge cloud within the cluster.

Molecular dynamic simulation for laser–cluster interaction

“…Recently some experiments are carried out by couple of groups on the interaction of atomic clusters with few cycle laser pulses ($10 fs), and it is observed that the ions with higher energy are emitted along the perpendicular to laser polarization direction. [29][30][31] Which is in complete contrast to the experiments performed with long pulses, where we obtain the asymmetry along the laser polarization direction. The understanding of the dynamics of few cycle laser pulses would be a matter of future investigation.…”

Molecular dynamic studies on anisotropic explosion of laser irradiated Xe cluster

“…6 Recently, anisotropy in the cluster explosion has been observed by a number of experimental groups for different cluster species (Xe, Ar, and H 2 ) and for various laser pulse durations. [7][8][9][10]12 For heavy clusters like Xe, a directional anisotropy in ion emission showing preference along laser polarization direction is observed for long pulse durations (hundreds of femtosecond) and it is explained by the laser induced surface polarization effects. 12 Results of anisotropic ion emission in Ar clusters are explained by "charge flipping" model.…”

Attosecond Nanophysics

“…Ultrafast processes resulting from the interaction of the laser with the particles can therefore be studied even up to conditions where the particles Coulomb explode after exposure to the laser pulse. Using few-cycle pulses allows us to restrict laser the interaction with the particles to a few femtoseconds and separates the laser-induced electron emission and acceleration from any electronic and nuclear dynamics taking place on longer timescales [33,34].…”

“…Though resonant plasmon enhancement is typical in strong-field laser-cluster experiments, its direct time-domain analysis has not been achieved yet. Such analysis is, however, important to advance the understanding of collective electronic processes in intense laser fields and their signatures in the electron and ion emission [57][58][59].…”