Ionization and expansion dynamics of atomic clusters irradiated with short intense VUV pulses

Abstract

Kinetic Boltzmann equations are used to model the ionization and expansion dynamics of xenon clusters irradiated with short intense VUV pulses. This unified model includes predominant interactions that contribute to the cluster dynamics induced by this radiation. The dependence of the evolution dynamics on cluster size, $N_{atoms}=20-90000$, and pulse fluence, $F=0.05-1.5$ J/cm${}^2$, corresponding to intensities in the range, $10^{12}-10^{14}$ W/cm${}^2$ and irradiation times, $\le 50$ fs, is investigated. The predictions obtained with our model are found to be in good agreement with the experimental data. We find that during the exposure the cluster forms a shell structure consisting of a positively charged outer shell and a core of net charge equal to zero. The width of these shells depends on the cluster size. The charged outer shell is large within small clusters ($N_{atoms}=20,70$), and its Coulomb explosion drives the expansion of these clusters. Within the large clusters ($N_{atoms}=2500,90000$) the neutral core is large, and after the Coulomb explosion of the outer shell it expands hydrodynamically. Highly charged ions within the core recombine efficiently with electrons. As a result, we observe a large fraction of neutral atoms created within the core, its magnitude depending on the cluster size.

4 pages, 2 figures

References in corpus (9)

• Femtosecond Diffractive Imaging with a Soft-X-ray Free-Electron Laser
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• Small rare gas clusters in soft X-ray pulses
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• Imaging atom-clusters by hard x-ray free electron lasers
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• Femtosecond non-equilibrium dynamics of clusters irradiated with short intense VUV pulses
• Interaction of intense vuv radiation with large xenon clusters
• Atomic clusters of various sizes irradiated with short intense pulses of VUV radiation

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• Multi-temperature atomic ensemble: nonequilibrium evolution after ultrafast electronic excitation
• Hydrodynamic model for expansion and collisional relaxation of x-ray laser-excited multi-component nanoplasma
• Modeling warm dense matter formation within tight binding approximation
• Multi-electron-recombination rates estimated within dense plasmas