Energy distributions of trapped atomic hydrogen

Doyle, John M.; Sandberg, Jon C.; Masuhara, N.; Yu, Ite A.; Kleppner, Daniel; Greytak, Thomas J.

doi:10.1364/josab.6.002244

Cited by 31 publications

(4 citation statements)

References 24 publications

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“…It could be experimentally tested, for instance, using an electric pulse to extract electrons (Roberts et al 2004; Vanhaecke et al 2005) similarly to ‘runaway electron’ experiments (Kulsrud et al 1973). A similar technique has been used in neutral atom BEC confined in a static external potential (Doyle et al 1989). The extraction should lead to an instantaneous picture of the energy distribution of the electrons in the plasma.…”

Section: Evaporation Experiments and Electron Temperature Measurementmentioning

confidence: 99%

Star cluster dynamics in a laboratory: electrons in an ultracold plasma

Comparat

Vogt

Mudrich

et al. 2005

Monthly Notices of the Royal Astronomical Society

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Electrons in a spherical ultracold, quasi‐neutral plasma at temperature in the Kelvin range can be created by laser excitation of an ultracold, laser‐cooled atomic cloud. The dynamical behaviour of the electrons is similar to the one described by conventional models of star cluster dynamics. The single mass component, the spherical symmetry and no star evolution are here accurate assumptions. The analogue of binary star formations in the cluster case is a three‐body recombination in Rydberg atoms in the plasma case with the same Heggie's law: soft binaries get softer and hard binaries get harder. We demonstrate that the evolution of such an ultracold plasma is dominated by Fokker–Planck kinetics equations formally identical to the ones controlling the evolution of a star cluster. The Virial theorem leads to a link between the plasma temperature and the ions and electron numbers. The Fokker–Planck equation is approximate using gaseous and fluid models. We found that the electrons are in a Kramers–Michie–King type quasi‐equilibrium distribution as stars in clusters. We suggest that the evaporation rate can be used to determine the temperature. As an example, knowing the electron distribution and using forced fast electron extraction, in a ‘violent extraction’ way, we are able to determine the plasma temperature knowing the trapping potential depth.

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Section: Evaporation Experiments and Electron Temperature Measurementmentioning

confidence: 99%

Star cluster dynamics in a laboratory: electrons in an ultracold plasma

Comparat

Vogt

Mudrich

et al. 2005

Monthly Notices of the Royal Astronomical Society

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“…This is close to the electron thermalisation time and we probably also extract some rethermalized electrons. A similar technique has been used in neutral atom Bose Einstein Condensation experiments in a static external potential [16]. Our case, electrons in the plasma, is more complex due to the fact our potential φ (sum of the electronic, ionic and external potential) depends on the number of particles trapped via Poisson's equation.…”

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confidence: 99%

Ionization of Rydberg atoms embedded in an ultracold plasma

et al. 2005

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We have studied the behavior of cold Rydberg atoms embedded in an ultracold plasma. We demonstrate that even deeply bound Rydberg atoms are completely ionized in such an environment, due to electron collisions. Using a fast pulse extraction of the electrons from the plasma we found that the number of excess positive charges, which is directly related to the electron temperature Te, is not strongly affected by the ionization of the Rydberg atoms. Assuming a Michie-King equilibrium distribution, in analogy with globular star cluster dynamics, we estimate Te. Without concluding on heating or cooling of the plasma by the Rydberg atoms, we discuss the range for changing the plasma temperature by adding Rydberg atoms.PACS numbers: 32.80. Pj, 52.25.Dg, 98.10.+z One challenge in ultra-cold plasma physics is to reach the correlated regime where the Coulomb energy dominates the kinetic energy. One suggested way, unfortunately limited to non alkali ions, is to cool the plasma ions by lasers [1]. An alternative way might be to use the binding energy of Rydberg states as "ice cubes" to cool the plasma. The physics of ultracold Rydberg gases [2,3] and ultracold plasmas [4] formed by laser excitation of a cold atomic sample have strong similarities. Indeed, Rydberg atom formation in an ultracold plasma [5] and spontaneous evolution of an ultracold Rydberg gas to plasma [6] have been demonstrated. The Rydberg ionization process starts with blackbody photoionization and initial electrons leave the cloud region. A second phase occurs when the positive ion potential is deep enough to trap subsequent electrons, which then collide with Rydberg atoms creating more electrons in an avalanche ionization process [7,8,9]. However, other relevant processes have been proposed whose effects need to be investigated, such as continuum lowering [10], and manybody effects or long-range interactions [11] that can lead to autoionization of Rydberg atom pairs [12].In this letter, we report the behavior of a mixture of an almost neutral ultracold plasma and a cold Rydberg atom sample. A related experiment has been reported, but in the case of rubidium Rydberg atoms created in a purely ionic plasma [13]. In this letter, we analyze the fast avalanche ionization of deeply bound Rydberg states embedded in a quasi-neutral plasma. We also study, with a theory based on analogy with globular star cluster dynamics, the evolution of the temperature of the plasma when Rydberg atoms are added.The cesium magneto-optical trap (MOT) apparatus has been described in a previous paper [6]. Two dye lasers pulses (Coumarin 500) that are focused to the cold atom cloud diameter excite atoms initially in the 6p 3/2 state. The time origin of the experiment is the first laser (L 1 ) pulse, with typical energy P 1 = 10 µJ, which creates a quasi-neutral plasma of N i ≈ 4 × 10 5 ions with peak density 10 10 cm −3 . The second laser (L 2 ) pulse (ASE < 1%), has a 18 ns delay and excites typically 4 × 10 5 Rydberg atoms. The Rydberg number fluctuates from pulse to pulse due to...

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“…The temperature [17] and density [16] are measured by rapidly lowering the trap threshold to zero while monitoring the power deposited on a bolometer. The power results from molecular recombination and is proportional to the flux of atoms escaping from the trap.…”

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confidence: 99%

Cold Collision Frequency Shift of the1S-2STransition in Hydrogen

et al. 1998

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We have observed the cold collision frequency shift of the 1S-2S transition in trapped spin-polarized atomic hydrogen. We find ∆ν 1S−2S = −3.8 ± 0.8 × 10 −10 n Hz cm 3 , where n is the sample density. From this we derive the 1S-2S s-wave triplet scattering length, a 1S−2S = −1.4 ± 0.3 nm, which is in fair agreement with a recent calculation. The shift provides a valuable probe of the distribution of densities in a trapped sample.

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Energy distributions of trapped atomic hydrogen

Cited by 31 publications

References 24 publications

Star cluster dynamics in a laboratory: electrons in an ultracold plasma

Star cluster dynamics in a laboratory: electrons in an ultracold plasma

Ionization of Rydberg atoms embedded in an ultracold plasma

Cold Collision Frequency Shift of the1S-2STransition in Hydrogen

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