Modeling many-particle mechanical effects of an interacting Rydberg gas

Amthor, Thomas; Reetz‐Lamour, M.; Giese, Christian; Weidemüller, Matthias

doi:10.1103/physreva.76.054702

Cited by 57 publications

(52 citation statements)

References 15 publications

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“…This assumption is consistent with our experimental observation that the Rydberg resonance does not significantly shift after plasma formation, but only becomes broadened [16]. On the observed timescale, the repulsive |55S 1/2 atoms are not expected to undergo ionizing Rydberg-Rydberg collisions at a sufficient rate to seed the avalanche [27]. Instead, we attribute the seed processes to a combination of blackbody photoionization [12] and ionizing collisions either with ground-state atoms or with the relatively large population in the intermediate state |5P 3/2 [23].…”

Section: Fig 1 (Color Online)supporting

confidence: 91%

Spontaneous Avalanche Ionization of a Strongly Blockaded Rydberg Gas

Robert-De-Saint-Vincent

Hofmann²,

Schempp³

et al. 2013

Phys. Rev. Lett.

110

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We report the sudden and spontaneous evolution of an initially correlated gas of repulsively interacting Rydberg atoms to an ultracold plasma. Under continuous laser coupling we create a Rydberg ensemble in the strong blockade regime, which at longer times undergoes an ionization avalanche. By combining optical imaging and ion detection, we access the full information on the dynamical evolution of the system, including the rapid increase in the number of ions and a sudden depletion of the Rydberg and ground state densities. Rydberg-Rydberg interactions are observed to strongly affect the dynamics of plasma formation. Using a coupled rate-equation model to describe our data, we extract the average energy of electrons trapped in the plasma, and an effective crosssection for ionizing collisions between Rydberg atoms and atoms in low-lying states. Our results suggest that the initial correlations of the Rydberg ensemble should persist through the avalanche. This would provide the means to overcome disorder-induced-heating, and offer a route to enter new strongly-coupled regimes.Ultracold plasmas (UCPs) formed by photo-ionizing ultracold neutral atomic or molecular gases [1,2] offer an ideal laboratory setting to better understand exotic phases of matter such as dense astrophysical plasmas [3] and laser induced plasmas [4]. Experimental and theoretical progress is driven by the potential to reach the so-called strongly-coupled regime [5,6], in which the Coulomb interaction energy dominates over the kinetic energy of the ions, giving rise to collective effects and strong spatial correlations between particles. It is quantified by the coupling parameter Γ = q 2 /4πǫ 0 ak B T ≫ 1, where a is the Wigner-Seitz radius, q the electron charge, and T the ion temperature. In laser-cooled gases, Γ ≈ 0.1 − 2 is readily achieved, which has allowed the observation and driving of collective mechanical modes [7]. Reaching deep into the strongly-coupled regime, however, has remained out of reach partly due to disorder-inducedheating (DIH), where the Coulomb interaction energy due to the initially random distribution of the atoms is converted into kinetic energy of the ions [8,9].Gases of atoms in high-lying (Rydberg) states offer an alternative approach to study UCPs, as they can be easily ionized, and the strong Rydberg-Rydberg interactions lead to dramatic new effects. The spontaneous evolution of an attractively interacting Rydberg gas into an UCP has been observed in several experiments [10,11], which initiated in-depth studies on the ionization mechanisms [12][13][14] and on the electron-ion recombination dynamics towards Rydberg states [15]. Recently [16], the long-term formation of an ionic cloud from attractive and repulsive Rydberg states has been observed, and its back-action onto Rydberg laser-excitation rates has been characterized. At the high densities achievable using optical or magnetic traps, the Rydberg blockade effect [17] gives rise to strong correlations in the initial gas [18]. Since these correlations resemble ...

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Section: Fig 1 (Color Online)supporting

confidence: 91%

Spontaneous Avalanche Ionization of a Strongly Blockaded Rydberg Gas

Robert-De-Saint-Vincent

Hofmann²,

Schempp³

et al. 2013

Phys. Rev. Lett.

110

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“…An isolated pair of atoms will be drawn apart immediately, so that the ionization probability is small. In a many-particle system where all atoms are repelling each other, each particle may come into the vicinity of other atoms several times while moving across the cloud [7]. This increases the average time spent at close distance and thus increases the ionization probability.…”

Section: Repulsive Many-particle Dynamicsmentioning

confidence: 99%

“…This is attributed to a series of resonant dipole-coupled pair states which may allow one of the atoms of a pair to ionize within a time much shorter than the timescale of interaction-induced motion. In more a Present address: Physikalisches Institut, Universität Heidelberg, Philosophenweg 12, 69120 Heidelberg, Germany dilute gases, simulations of atom trajectories in manyparticle systems are found to underestimate the observed ionization rate at high principal quantum numbers [7]. Apparently there exists a distance-dependent coupling of two-particle or many-particle states to other states involving the continuum.…”

Section: Introductionmentioning

confidence: 99%

“…The dynamics of the system is then calculated by solving the equations of motion for all atoms according to the van der Waals interaction potentials in the same way as described in Ref. [7], and the results are averaged over 50 runs of the simulation. For typical nearest-neighbor distances of about 4 µm, the surrounding atoms in this example enhance the probability to ionize within 30 µs by roughly a factor of 1.4.…”

Section: Repulsive Many-particle Dynamicsmentioning

confidence: 99%

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Autoionization of an ultracold Rydberg gas through resonant dipole coupling

et al. 2009

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Abstract. We investigate a possible mechanism for the autoionization of ultracold Rydberg gases, based on the resonant coupling of Rydberg pair states to the ionization continuum. Unlike an atomic collision where the wave functions begin to overlap, the mechanism considered here involves only the long-range dipole interaction and is in principle possible in a static system. It is related to the process of intermolecular Coulombic decay (ICD). In addition, we include the interaction-induced motion of the atoms and the effect of multi-particle systems in this work. We find that the probability for this ionization mechanism can be increased in many-particle systems featuring attractive or repulsive van der Waals interactions. However, the rates for ionization through resonant dipole coupling are very low. It is thus unlikely that this process contributes to the autoionization of Rydberg gases in the form presented here, but it may still act as a trigger for secondary ionization processes. As our picture involves only binary interactions, it remains to be investigated if collective effects of an ensemble of atoms can significantly influence the ionization probability. Nevertheless our calculations may serve as a starting point for the investigation of more complex systems, such as the coupling of many pair states proposed in [1].

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“…This is quantified in Fig. 6 Rydberg atoms with repulsive interactions are known to Penning ionize and produce plasma [68,72,73], but at a much slower rate than for attractive potentials [73]. However, because this growth is slow, other processes must be considered that might contribute to the growth in the number of visible ion cores after 1 D 2 excitations, such as population redistribution to states with attractive potentials by blackbody radiation (BBR) and BBR-induced photoionization.…”

Section: Rydberg Gas Dynamics With Attractive and Repulsive Interamentioning

confidence: 99%

Imaging the evolution of an ultracold strontium Rydberg gas

et al. 2013

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Clouds of ultracold strontium 5s48s 1 S 0 or 5s47d 1 D 2 Rydberg atoms are created by two-photon excitation of laser-cooled 5s 2 1 S 0 atoms. The spontaneous evolution of the cloud of low orbital angular momentum (low-) Rydberg states towards an ultracold neutral plasma is observed by imaging resonant light scattered from core ions, a technique that provides both spatial and temporal resolution. Evolution is observed to be faster for the S states, which display isotropic attractive interactions, than for the D states, which exhibit anisotropic, principally repulsive interactions. Immersion of the atoms in a dilute ultracold neutral plasma speeds up the evolution and allows the number of Rydberg atoms initially created to be determined.

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Modeling many-particle mechanical effects of an interacting Rydberg gas

Cited by 57 publications

References 15 publications

Spontaneous Avalanche Ionization of a Strongly Blockaded Rydberg Gas

Spontaneous Avalanche Ionization of a Strongly Blockaded Rydberg Gas

Autoionization of an ultracold Rydberg gas through resonant dipole coupling

Imaging the evolution of an ultracold strontium Rydberg gas

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