Mobility of Electrons in Low-Temperature Helium Gas

Levine, James L.; Sanders, T. M.

doi:10.1103/physrev.154.138

Cited by 246 publications

(61 citation statements)

References 23 publications

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“…This void is often referred to as a bubble and it has typical radii between 10-14 Å depending on the electron's orbital radius [14]. Bubbles of similar type are well known to enclose electrons in liquid and even dense gaseous helium [15][16][17]. Within the confinement of these bubbles the perturbation by surrounding ground state helium atoms is low and the electronic life time of the excited atoms or excimers is almost similarly long as for free species in the vacuum.…”

Section: Introductionmentioning

confidence: 99%

Luminescence from Liquid Helium Excited by Corona Discharges

Bonifaci

Aitken

et al. 2009

IEEE Trans. Dielect. Electr. Insul.

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Liquid helium (LHe) at 4.2 K was electronically excited using a corona discharge for both negative and positive high voltages. The experiments were carried out for different pressures in the range from 0.1 to 10 MPa at constant temperature. The light emitted from the zone close to the tip was spectroscopically analyzed showing features from atoms and excimer helium. The shifts and widths of the observed lines and bands were found to depend on the applied hydrostatic pressure and on the tip polarity. Our analysis showed that classic pressure broadening theory cannot account for the observed widths and shifts rather than the presence of bubbles which surround single excited atoms and molecules. For positive tip polarities red shifted features distinct from pure He and He 2 * were observed and tentatively assigned to "red satellites".

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Section: Introductionmentioning

confidence: 99%

Luminescence from Liquid Helium Excited by Corona Discharges

Bonifaci

Aitken

et al. 2009

IEEE Trans. Dielect. Electr. Insul.

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“…The single electron bubble formation proves energetically favourable at sufficiently low temperatures and sufficiently high densities (threshold values of temperature and density follow the relation n T 2 3 / ), and all the parameters of arising bubble well satisfy the adopted assumptions: the bubble size is much larger than the interatomic distance, the free energy minimum depth substantially exceeds temperature, etc. We omit any quantitative details since for a 0 0 > the non-linearity of V n 0 ( ) does not introduce any qualitative corrections to the bubble parameters and the resulting picture is practically identical to that obtained earlier [11,12].…”

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confidence: 63%

“…Formally, the problem of finding the ground state of a single electron in the gaseous media reduces to minimizing the free energy F of the entire «electron+gas» system with respect to variations of the (spherically symmetric) electron wave function y( ) r and gas atom number density n r ( ) [11,12],…”

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confidence: 99%

“…For single electron bubbles, where a 0 0 > , this program was realized in [11,12] where the linear approximation for V 0 was employed. The single electron bubble formation proves energetically favourable at sufficiently low temperatures and sufficiently high densities (threshold values of temperature and density follow the relation n T 2 3 / ), and all the parameters of arising bubble well satisfy the adopted assumptions: the bubble size is much larger than the interatomic distance, the free energy minimum depth substantially exceeds temperature, etc.…”

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confidence: 99%

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Localized electrons in dense heavy noble gases

Nazin

Shikin

2009

Low Temperature Physics

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The paper addresses counterintuitive behavior of electrons injected into dense cryogenic media with negative scattering length a 0 . Instead of expected polaronic effect (formation of density enhancement clusters) which should substantially reduce the electron mobility, an opposite picture is observed: with increasing | | a 0 (the trend taking place for inert gases with the growth of atomic number) and the medium density, the electrons remain practically free. An explanation of this behavior is provided based on consistent accounting for the non-linearity of electron interaction with the gaseous medium in the gas atom number density.PACS: 71.10.-w Theories and models of many-electron systems.Keywords: delocalized electron, heavy inert gases, negativ scattering length.One of the most interesting and still important issues in physics of cryogenic media is the problem of electron clusters which emerged almost simultaneously with that of electron bubbles. However, it is much less transparent (compared to the case of electron bubbles) from the experimental side. Although there are some indications of the existence of electron clusters in xenon [1], they are not observed on the expected scale in media with comparatively high atomic polarizabilities (krypton, xenon) which are presumably likely to develop various electron autolocalization phenomena. On the contrary, the data on electron mobility in Ar, Kr, and Xe [2-4] reveal that electrons remain practically free (compared to mobility of positive ions possessing the structure of massive polaronic-type formations) in their motion, at least in the vicinity of the characteristic electron mobility peak which is observed for all heavy inert gases.The existing description [5][6][7] of electron clusters in cryogenic media with negative scattering lengths a 0 employs the well-known approximation [8,9] for electron-medium interaction energy which is linear in the gas density n. Within this approximation, the minimal energy V 0 of delocalized electron injected into the gaseous media is calculated aswhere m is the free electron mass. In terms of electron energy bands in solids, V 0 is the conduction band bottom energy. The case of a 0 0 > corresponds to formation a single-electron bubble. On the other hand, a density enhancement domain with higher gas atom concentration (i.e., a cluster) may develop around the electron if a 0 0 < . The authors of Refs. 5-7 made every effort to provide a quantitatively accurate description of the gas density around the localized electron in the linear approximation. In addition to (1), they also introduced a non-local electron-gas interaction of the typewhere y( ) r is the electron wave function, took into account the deviation of the gas entropy contribution to the total free energy from the ideal gas, etc. Their final conclusions [5][6][7] practically coincide with the intuitively expected picture: the electron cluster should exist, and the electron localization degree as well as the cluster mass should monotonously grow with the density media a...

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“…(1). Anomalous density effects have been experimentally observed in a number of compressed gases [2][3][4][5][6][7][8][9][10][11][12][13]. A negative density effect, i.e., the density-normalized mobility at thermal energies, 0 N, decreases with incresing N at constant T (and eventually drops rapidly to very low values because of the formation of localized electron states), is shown by gases, such as He and Ne, whose interaction with the excess electrons is dominated by the short-range repulsive exchange forces.…”

Section: Introductionmentioning

confidence: 99%

Electron mobility in dense Argon gas at several temperatures

Borghesani

Lamp²

Proceedings of 2002 IEEE 14th International Conference on Dielectric Liquids. ICDL 2002 (Cat. No.02CH37319)

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The mobility of excess electrons in dense Argon gas has been measured as a function of the applied electric field E and of the gas density N at several temperatures in the range 142.6T c and the small negative effect previously observed for T 90 K. In any case, the data at all temperatures confirm the interpretation of the anomalous density effect as being essentially due by the density-dependent quantum shift of the electron ground state kinetic energy in a disordered medium as a result of multiple scattering (MS) processes, although other MS processes do influence the outcome of the experiment.

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Mobility of Electrons in Low-Temperature Helium Gas

Cited by 246 publications

References 23 publications

Luminescence from Liquid Helium Excited by Corona Discharges

Luminescence from Liquid Helium Excited by Corona Discharges

Localized electrons in dense heavy noble gases

Electron mobility in dense Argon gas at several temperatures

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