Observation of shells in Coulomb explosions of rare-gas clusters

Erk, Benjamin; Hoffmann, K.; Kandadai, Nirmala; Helal, A.; Keto, John W.; Ditmire, T.

doi:10.1103/physreva.83.043201

Cited by 13 publications

(7 citation statements)

References 21 publications

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“…Among the most interesting effects of laser illumination of metal clusters is the emission of higher harmonics of the laser radiation [85], the emission of energetic electrons and, in case of strong ionization, Coulomb explosion of the whole cluster [86]. A similar rapid expansion of Coulomb and Yukawa dust clusters has been recently predicted in Ref.…”

Section: Finite Dust Clusters and Comparison With Metal Clusterssupporting

confidence: 63%

Controlling strongly correlated dust clusters with lasers

Thomsen

Ludwig

Bönitz

et al. 2014

J. Phys. D: Appl. Phys.

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Lasers have been used extensively to manipulate matter in a controlled way -from single atoms and molecules up to macroscopic materials. They are particularly valuable for the analysis and control of mesoscopic systems such as few-particle clusters. Here we report on recent work on finite size complex (dusty) plasma systems. These are unusual types of clusters with very strong inter-particle interaction so that, at room temperature, they are practically in their ground state. Lasers are employed as a tool to achieve excited states and phase transitions.The most attractive feature of dusty plasmas is that they allow for a precise diagnostic with single-particle resolution. From such measurements, the structural properties of finite two-dimensional (2D) clusters and three-dimensional (3D) spherical crystals in nearly harmonic traps-so-called Yukawa balls-have been explored in great detail. Their structural features-the shell compositions and the order within the shells-have been investigated and good agreement to theoretical predictions was found. Open questions on the agenda are the excitation behavior, the structural changes, and phase transitions that occur at elevated temperature.Here we report on recent experimental results where laser heating methods were further improved and applied to finite 2D and 3D dust clusters. Comparing to simulations, we demonstrate that laser heating indeed allows to increase the temperature in a controlled manner. For the analysis of thermodynamic properties and phase transitions in these finite systems, we present theoretical and experimental results on the basis of the instantaneous normal modes, pair distribution function and the recently introduced center-two-particle correlation function.arXiv:1402.7182v2 [physics.plasm-ph] 7 Jul 2014 ‡ Strictly, the definition (1) is an appropriate measure for the potential energy only when the pair interaction is Coulombic. In the case of screening, the effective coupling parameter depends on the screening length λ D [7]. For the results reported in this paper, the dust-dust interaction is moderately screened and the definition (1) is sufficiently accurate.

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Section: Finite Dust Clusters and Comparison With Metal Clusterssupporting

confidence: 63%

Controlling strongly correlated dust clusters with lasers

Thomsen

Ludwig

Bönitz

et al. 2014

J. Phys. D: Appl. Phys.

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“…The characteristic signature of a lychee core is its intense low-energy peak in the ion kinetic energy distribution. Such low-energy peaks are exhibited in the ion kinetic energy distributions of Erk et al [50], which deserve further analysis. In case of non-vertical outer ionization by short pulses (example (B)), the lychee model shows very poor numerical agreement with the simulation results but was very useful in interpreting and characterizing the underlying physical processes.…”

Section: Discussionmentioning

confidence: 82%

“…Erk et al [50] have recently published experimentally obtained ion kinetic energy distributions (KEDs) for xenon and argon clusters. To make contact with their experimental results, the simulated single-trajectory KEDs must be doubly averaged over the cluster size distribution and over the laser intensity profile [22].…”

Section: Simulation Resultsmentioning

confidence: 99%

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Ion energetics in electron-rich nanoplasmas

2012

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Based on trajectory calculations of xenon clusters up to ≈ 6000 atoms irradiated by laser pulses (peak intensities I M = 10 14 -10 16 W cm −2 , Gaussian pulse lengths τ = 10-230 fs and frequency 0.35 fs −1 ), we have analyzed the interrelation between outer ionization and ion kinetic energies. The following three main categories have been identified. (A) For short pulses (τ = 10 fs) of higher intensity I M = 10 16 W cm −2 , the outer ionization level leads to a sufficiently high positive cluster charge, which confines the remaining nanoplasma electrons to the cluster center. In this case, ion energies can be reasonably well accounted for by a multi-charge state lychee model, according to which outer ionization is vertical and the nanoplasma can be described by a non-expanding neutral cluster interior, causing a zero-energy component in the ion kinetic energy distribution and an expanding electron-free cluster periphery. (B) For a very low outer ionization level, which is realized for short pulses of low intensity (I M = 10 14 W cm −2 ) and/or large clusters, a slow gradual evaporation of nanoplasma electrons under laser-free conditions on the picosecond time scale is observed, making the entire outer ionization process highly non-vertical despite the short laser pulse. Accordingly, ions are accelerated only by a gradual buildup of the total cluster charge. (C) For long pulses (τ = 230 fs), the cluster expansion during the laser pulse is large and outer ionization is non-vertical. The nanoplasma electrons attain high kinetic energies by resonance heating and are distributed over the entire ion framework without a neutral cluster interior. Consequently, a zero-energy component in the ion energy distribution is missing.

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“…As a matter of fact, numerical simulations reveal that there is a faint border between the two mechanisms [33]. Moreover, when non-uniform expansion processes are considered, the cluster dynamics becomes extremely complicated, since shock ion shells can be predicted [34] and have been also indirectly observed in the ion kinetic energy distribution of exploding clusters [35]. Further complications in the modelling of cluster dynamics come from transient phenomena such as inner three-body recombination [17] and macroscopic effects as the interaction among ions and Rydberg excited clusters [36].…”

Section: Cluster Expansionmentioning

confidence: 99%

CO₂exploding cluster dynamics probed by XUV fluorescence

et al. 2014

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Clusters excited by intense laser pulses are a unique source of warm dense matter, that has been the subject of intensive experimental studies. The majority of these investigations concern atomic clusters, whereas the evolution of molecular clusters excited by intense laser pulses is less explored. In this work we trace the dynamics of CO 2 clusters triggered by a few-cycle μ 1.45 m driving pulse through the detection of XUV fluorescence induced by a delayed 800 nm ignition pulse. Striking differences among fluorescence dynamics from different ionic species are observed.

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Observation of shells in Coulomb explosions of rare-gas clusters

Cited by 13 publications

References 21 publications

Controlling strongly correlated dust clusters with lasers

Controlling strongly correlated dust clusters with lasers

Ion energetics in electron-rich nanoplasmas

CO₂exploding cluster dynamics probed by XUV fluorescence

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Observation of shells in Coulomb explosions of rare-gas clusters

Cited by 13 publications

References 21 publications

Controlling strongly correlated dust clusters with lasers

Controlling strongly correlated dust clusters with lasers

Ion energetics in electron-rich nanoplasmas

CO2exploding cluster dynamics probed by XUV fluorescence

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CO₂exploding cluster dynamics probed by XUV fluorescence