Recombination effects in soft-x-ray cluster interactions at the xenon giant resonance

Ackad, Edward; Bigaouette, Nicolas; Mack, Stephanie; Popov, K. G.; Ramunno, Lora

doi:10.1088/1367-2630/15/5/053047

Cited by 20 publications

(30 citation statements)

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“…When the classical binding becomes stronger, the classical electron is removed and the occupation number of the corresponding orbital is incremented by one. Although treating recombination the above way is somewhat phenomenological (e.g., no cross section derived from inverse processes is used), in particle simulations similar treatments are common [39][40][41].…”

Section: B Impact Ionization and Recombinationmentioning

confidence: 99%

Molecular-dynamics approach for studying the nonequilibrium behavior of x-ray-heated solid-density matter

et al. 2017

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When matter is exposed to a high-intensity x-ray free-electron-laser pulse, the x rays excite inner-shell electrons leading to the ionization of the electrons through various atomic processes and creating high-energy-density plasma, i.e., warm or hot dense matter. The resulting system consists of atoms in various electronic configurations, thermalizing on sub-picosecond to picosecond timescales after photoexcitation. We present a simulation study of x-ray-heated solid-density matter. For this we use XMDYN, a Monte-Carlo molecular-dynamics-based code with periodic boundary conditions, which allows one to investigate non-equilibrium dynamics. XMDYN is capable of treating systems containing light and heavy atomic species with full electronic configuration space and 3D spatial inhomogeneity. For the validation of our approach we compare for a model system the electron temperatures and the ion charge-state distribution from XMDYN to results for the thermalized system based on the average-atom model implemented in XATOM, an abinitio x-ray atomic physics toolkit extended to include a plasma environment. Further, we also compare the average charge evolution of diamond with the predictions of a Boltzmann continuum approach. We demonstrate that XMDYN results are in good quantitative agreement with the above mentioned approaches, suggesting that the current implementation of XMDYN is a viable approach to simulate the dynamics of x-ray-driven non-equilibrium dynamics in solids. In order to illustrate the potential of XMDYN for treating complex systems we present calculations on the triiodo benzene derivative 5-amino-2,4,6-triiodoisophthalic acid (I3C), a compound of relevance of biomolecular imaging, consisting of heavy and light atomic species.2

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Section: B Impact Ionization and Recombinationmentioning

confidence: 99%

Molecular-dynamics approach for studying the nonequilibrium behavior of x-ray-heated solid-density matter

et al. 2017

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“…Thus, this more stringent test of the change in the ionization energy approximated by the simple LIT model of argon in a cluster demonstrates its usefulness and accuracy in laser-cluster interaction modeling. 16 …”

Section: Resultsmentioning

confidence: 99%

“…Further, the implementation of LIT model is straight-forward and may easily include all cluster particles (including electrons) with results that agree well with experiments. 4,9,15,16 Atoms and ions in nanoplasmas will also have their ionization probabilities further altered due to electron and ion screening. 17,18 There have largely been two methodologies for dealing with these changes.…”

Section: Introductionmentioning

confidence: 99%

“…Further, the LIT model is easily implemented in atomistic-scale calculations and has met with good success in matching the results of experimental cluster studies. 16 The LIT model also leads to a precise definition for the inner-ionization threshold, an integral part of quantumclassical hybrid models of laser-cluster interactions which seek to describe the microscopic, time-dependent interaction of ultra-intense lasers with clusters. An accurate model of ionization will, thus, significantly improve the confidence in the transient properties of the laser-cluster interaction, which are now being probed experimentally, [25][26][27] and not just the final products.…”

Section: Introductionmentioning

confidence: 99%

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A validation of a simple model for the calculation of the ionization energies in X-ray laser-cluster interactions

White

Ackad

2015

Physics of Plasmas

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The outer-ionization of an electron from a cluster is an unambiguous quantity, while the inner-ionization threshold is not, resulting in different microscopic quantum-classical hybrid models used in laser-cluster interactions. A simple local ionization threshold model for the change in the ionization energy is proposed and examined, for atoms and ions, at distances in between the initial configuration of the cluster to well into the cluster's disintegration. This model is compared with a full Hartree-Fock energy calculation which accounts for the electron correlation effects using the coupled cluster method with single and double excitations with perturbative triples (CCSD(T)). Good agreement is found between the two lending a strong theoretical support to works which rely on such models for the final and transient properties of the laser-cluster interaction.

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“…For instance, the generation of seed electrons in a cluster by an extreme-ultraviolet (XUV) pulse allows the time-resolved investigation of strong-field processes induced by near-infrared (NIR) pulses [5]. Amongst the various processes that take place during the cluster expansion, electron-ion recombination processes are known to play an important role [1,3,[6][7][8][9]. Recently, recombination resulting in the production of a large number of excited atoms and ions was temporally resolved using pump-probe photoion and -electron spectroscopy [10][11][12], showing similar dynamics for clusters ionized by intense XUV and intense NIR pulses, respectively.…”

mentioning

confidence: 99%

Tracing transient charges in expanding clusters

Schütte¹,

Vrakking²,

Rouzée³

2017

Phys. Rev. A

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We study transient charges formed in methane clusters following ionization by intense nearinfrared laser pulses. Cluster ionization by 400 fs (I = 1 × 10 14 W/cm 2 ) pulses is highly efficient, resulting in the observation of a dominant C 3+ ion contribution. The C 4+ ion yield is very small, but is strongly enhanced by applying a time-delayed weak near-infrared pulse. We conclude that most of the valence electrons are removed from their atoms during the laser-cluster interaction, and that electrons from the nanoplasma recombine with ions and populate Rydberg states when the cluster expands, leading to a decrease of the average charge state of individual ions. Furthermore, we find clear bound-state signatures in the electron kinetic energy spectrum, which we attribute to Auger decay taking place in expanding clusters. Such nonradiative processes lead to an increase of the final average ion charge state that is measured in experiments. Our results suggest that it is crucial to include both recombination and nonradiative decay processes for the understanding of recorded ion charge spectra.The ionization of clusters by intense laser pulses induces highly complex dynamics that take place on attosecond to nanosecond timescales and that involve a large number of interacting particles. Intense lasercluster interactions commonly involve an ionization stage, the establishment of a nanoplasma and the subsequent expansion and break-up of this nanoplasma. Disentangling the different mechanisms is a very challenging task that requires sophisticated theoretical and experimental approaches. In spite of the large efforts that have been devoted to the study of laser-cluster interactions in the past 20 years (see e.g. [1-4]), the understanding of both the ionization and relaxation dynamics taking place during the cluster expansion are still far from being complete. For instance, up to now, experiments have only provided limited information about the relative importance of direct laser-induced (multi-photon and tunneling) ionization and electron-impact ionization by laserdriven electron-atom/ion collisions The development and application of pump-probe techniques promises novel insights into the relevant processes. For instance, the generation of seed electrons in a cluster by an extreme-ultraviolet (XUV) pulse allows the time-resolved investigation of strong-field processes induced by near-infrared (NIR) pulses [5]. Amongst the various processes that take place during the cluster expansion, electron-ion recombination processes are known to play an important role [1,3,[6][7][8][9]. Recently, recombination resulting in the production of a large number of excited atoms and ions was temporally resolved using pump-probe photoion and -electron spectroscopy [10][11][12], showing similar dynamics for clusters ionized by intense XUV and intense NIR pulses, respectively. These results suggest that the charge distributions that can be measured after the nanoplasma has expanded may differ significantly from the transient charge distributions ...

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Recombination effects in soft-x-ray cluster interactions at the xenon giant resonance

Cited by 20 publications

References 28 publications

Molecular-dynamics approach for studying the nonequilibrium behavior of x-ray-heated solid-density matter

Molecular-dynamics approach for studying the nonequilibrium behavior of x-ray-heated solid-density matter

A validation of a simple model for the calculation of the ionization energies in X-ray laser-cluster interactions

Tracing transient charges in expanding clusters

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