Strong-coupling effects in the relaxation dynamics of ultracold neutral plasmas

Pohl, Thomas; Pattard, Thomas

doi:10.1088/1742-6596/11/1/022

Cited by 7 publications

(14 citation statements)

References 33 publications

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“…Hence, it provides better temporal and spatial resolution of T i than the experimental optical probes. As was shown in [73,29], the ion temperature shows clear oscillations in space (i.e. as a function of the distance from the center of the plasma) and, in fact, a wavelike oscillation pattern emanating from the plasma center (Fig.…”

Section: Kinetic Energy Oscillationssupporting

confidence: 55%

“…Such collisions can however be incorporated into the PICtreatment on the basis of the collision integrals introduced in Eqs. ( 27)- (29). Within such so-called particle-in-cell-Monte-Carlo-collision simulations (PICMCC) [86] the collision terms in Eq.…”

Section: Particle-in-cell Approachesmentioning

confidence: 99%

“…The low density implies that ultracold plasmas evolve on a time scale that is more easily accessible experimentally. Studies of ion equilibration have revealed oscillations of the ion kinetic energy [28,29,30,31] that are a fundamental characteristic of equilibration of strongly coupled systems. Expansion of a plasma into the surrounding vacuum may be directly observed with excellent spatial and temporal resolution in ultracold systems [32,33,34,13].…”

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confidence: 99%

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Ultracold neutral plasmas

Killian¹,

Chen²,

Gupta³

et al. 2005

Plasma Phys. Control. Fusion

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Ultracold neutral plasmas, formed by photoionizing laser-cooled atoms near the ionization threshold, have electron temperatures in the 1-1000 kelvin range and ion temperatures from tens of millikelvin to a few kelvin. They represent a new frontier in the study of neutral plasmas, which traditionally deals with much hotter systems, but they also blur the boundaries of plasma, atomic, condensed matter, and low temperature physics. Modelling these plasmas challenges computational techniques and theories of non-equilibrium systems, so the field has attracted great interest from the theoretical and computational physics communities. By varying laser intensities and wavelengths it is possible to accurately set the initial plasma density and energy, and charged-particle-detection and optical diagnostics allow precise measurements for comparison with theoretical predictions.Recent experiments using optical probes demonstrated that ions in the plasma equilibrate in a strongly coupled fluid phase. Strongly coupled plasmas, in which the electrical interaction energy between charged particles exceeds the average kinetic energy, reverse the traditional energy hierarchy underlying basic plasma concepts such as Debye screening and hydrodynamics. Equilibration in this regime is of particular interest because it involves the establishment of spatial correlations between particles, and it connects to the physics of the interiors of gas-giant planets and inertial confinement fusion devices.

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Section: Kinetic Energy Oscillationssupporting

confidence: 55%

Section: Particle-in-cell Approachesmentioning

confidence: 99%

mentioning

confidence: 99%

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Ultracold neutral plasmas

Killian¹,

Chen²,

Gupta³

et al. 2005

Plasma Phys. Control. Fusion

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“…Meanwhile, theoretical approaches have been developed for the description of various aspects of the dynamics of ultracold plasmas which are in very good agreement with experimental observations [8,11]. The time evolution of macroscopic properties, such as temperatures, densities, expansion velocities etc.…”

Section: Introductionsupporting

confidence: 52%

Electron–ion recombination in strongly coupled cold plasmas under nonequilibrium conditions

Pohl¹,

Pattard²

2006

J. Phys. A: Math. Gen.

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Abstract. We discuss the dynamics of recombination of an expanding ultracold plasma into highly excited Rydberg states, with emphasis on the influence of possible strong coupling between the charges and the nonequilibrium character of the electronic component. While the former does not significantly affect recombination in current experimental scenarios, the latter is shown to have a considerable influence on the system dynamics. We derive correction factors quantifying the deviation of collision rates from their respective equilibrium values. The experimentally observed unexpectedly high recombination rate at long evolution times can be reproduced by a proper inclusion of these effects without the need to invoke alternative, previously suggested mechanisms, such as an "adiabatic motion recombination" or the development of very strong electron correlations by collisional cooling.

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“…To approximately describe the long-time evolution of an expanding plasma we can refer to the Vlasov equations [11,5]:…”

Section: Expansion and Electron Temperaturementioning

confidence: 99%

On the formation and decay of a molecular ultracold plasma

Saquet

Morrison

Schulz-Weiling

et al. 2011

J. Phys. B: At. Mol. Opt. Phys.

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Abstract.Double-resonant photoexcitation of nitric oxide in a molecular beam creates a dense ensemble of 50f (2) Rydberg states, which evolves to form a plasma of free electrons trapped in the potential well of an NO + spacecharge. The plasma travels at the velocity of the molecular beam, and, on passing through a grounded grid, yields an electron time-of-flight signal that gauges the plasma size and quantity of trapped electrons. This plasma expands at a rate that fits with an electron temperature as low as 5 K, colder that typically observed for atomic ultracold plasmas. The recombination of molecular NO + cations with electrons forms neutral molecules excited by more than twice the energy of the NO chemical bond, and the question arises whether neutral fragmentation plays a role in shaping the redistribution of energy and particle density that directs the short-time evolution from Rydberg gas to plasma. To explore this question, we adapt a coupled rate-equations model established for atomic ultracold plasmas to describe the energy-grained avalanche of electron-Rydberg and electron-ion collisions in our system. Adding channels of Rydberg predissociation and two-body, electron-cation dissociative recombination to the atomic formalism, we investigate the kinetics by which this relaxation distributes particle density and energy over Rydberg states, free electrons and neutral fragments. The results of this investigation suggest some mechanisms by which molecular fragmentation channels can affect the state of the plasma.

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Strong-coupling effects in the relaxation dynamics of ultracold neutral plasmas

Cited by 7 publications

References 33 publications

Ultracold neutral plasmas

Ultracold neutral plasmas

Electron–ion recombination in strongly coupled cold plasmas under nonequilibrium conditions

On the formation and decay of a molecular ultracold plasma

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