共查询到20条相似文献,搜索用时 31 毫秒
1.
V. B. Shikin 《JETP Letters》1998,68(10):799-803
The problem of the stability of a massive, charged helium film is studied with allowance for the possible motion of the film
relative to the electron system localized on its surface. Here a peculiar sort of Doppler effect is intertwined with processes
that cause the charged helium surface to become unstable, affecting its critical characteristics.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 10, 759–762 (25 November 1998) 相似文献
2.
Negative Ca− and Ba− ions of large radii on the surface of and in bulk liquid helium have been studied. Our results indicate that these ions are
adsorbed on the helium surface. Ions on free liquid helium surfaces have not been studied previously because it was thought
impossible to confine them on the surface. Ca− and Ba− ions have very low binding energies, therefore, like electrons, they form a bubble of large radius in bulk helium, whose
energy is higher than on the surface. The behavior of ions on the surface exhibits a number of previously unknown features
owing to their large masses and strong localization in the horizontal plane. Even in the absence of confining electric field,
a hole is formed under an ion due to the polarization attraction between the liquid helium and the charged ion. This hole
formation reduces the ion mobility by several orders of magnitude and increases its effective mass severalfold. The critical
density of electrons and ions is approximately the same on the surfaces of thin and thick helium films.
Zh. éksp. Teor. Fiz. 115, 593–604 (February 1999) 相似文献
3.
A. B. Voitkiv 《Journal of Experimental and Theoretical Physics》1997,85(6):1074-1080
Ionization of hydrogen and helium atoms is studied for the case of “soft” collisions with highly charged fast ions with v≲Z≪v2 and v≫v
0, where Z is the ion charge, v is the collision velocity, and v
0∼1 is the characteristic velocity of the electron in the ground state of the atom. Analytical expressions are derived for
the singly and doubly differential cross section for ionization of a hydrogen atom accompanied by the ejection of a slow electron
v
e≲v
0, where v
e is the velocity of the ejected electron with respect to the recoil ion). The results are generalized to the case of single
ionization of helium. It is shown that soft collisions provide the main contribution to the hydrogen ionization cross section
and for all practical purposes determine the cross section for single ionization of helium. The asymmetry in the angular distribution
of the ejected slow electrons and the properties of momentum exchange in such collisions are discussed. Finally, a formula
for the cross section for single ionization of helium is proposed.
Zh. éksp. Teor. Fiz. 112, 1966–1977 (December 1997) 相似文献
4.
A nonstationary theory of double ionization of two-electron atoms in collisions with multiply charged ions or by an intense
electromagnetic field is developed. An approach that permits investigating both problems by a single method is formulated.
A two-electron continuum wave function that takes into account the interaction of the electrons with the atomic nucleus and
the external ionizer as well as with one another is obtained as a product of Coulomb waves with modified Sommerfeld parameters.
The computational results obtained for the double ionization of helium atoms by multiply charged ions are in good quantitative
agreement with the existing experimental data.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 1, 23–26 (10 July 1997) 相似文献
5.
Photographs of pulsed microwave discharges initiated by a metallic sphere placed at the focus of a quasioptical electromagnetic
beam with linear polarization of the field in air, sulfur hexafluoride, hydrogen, and helium under a pressure of several hundred
Torr are presented. The common and distinctive features of the discharges in these gases are noted.
Zh. Tekh. Fiz. 68, 33–36 (April 1998) 相似文献
6.
I. V. Vinyar 《Technical Physics》1999,44(5):511-515
A ten-barrel pneumatic injector for periodic introduction of fuel pellets into steady-state thermonuclear experiments has
been developed. Solid hydrogen pellets with diameters of 2.7 mm and lengths of 3 to 4 mm are formed in each barrel at a rate
of 0.1–0.2 Hz with periodic pulsed heating of a porous insert, which is continuously filled with hydrogen and cooled with
liquid helium, and accelerated to 1–1.2 km/s.
Zh. Tekh. Fiz. 69, 35–39 (May 1999) 相似文献
7.
A. B. Voitkiv 《Technical Physics》1998,43(3):265-270
Expressions for the cross sections for single and double ionization of atomic helium in collisions with fast multiply charged
ions are obtained in the collision parameter range υ
2≫Z≳υ, υ
0<c, where Z and υ are, respectively, the ion charge and ion velocity, υ
0 is the characteristic velocity of electrons in the atomic helium ground state, and c is the velocity of light.
Zh. Tekh. Fiz. 68, 1–7 (March 1998) 相似文献
8.
D. V. Afanas’ev A. A. Bogdanov G. A. Dyuzhev V. I. Karataev A. A. Kruglikov D. Deininger 《Technical Physics》1999,44(12):1440-1443
The production of fullerenes in an arc with graphite electrodes in mixtures of helium with oxygen and hydrogen as well as
in pure oxygen and hydrogen is investigated. The radiation spectra of the arc and the mass spectra of the soot obtained in
the arc are recorded; the content of fullerenes in the soot is determined. It is shown that fullerenes are formed in appreciable
quantities (∼1%) even in pure hydrogen.
Zh. Tekh. Fiz. 69, 48–51 (December 1999) 相似文献
9.
V. B. Shikin 《JETP Letters》1999,70(4):283-287
The reasons why supersaturated states appear for a 2D electron system on a liquid-helium surface and the possibility of stationary
existence of such states are discussed. The main characteristics of a 2D electron system on helium under stationary saturation
conditions are calculated. It is shown that the well-known saturation state for electrons above helium is one of a continuum
of supersaturated states. The experimental possibilities for observing and identifying supersaturated states for electrons
on a helium surface are noted.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 4, 274–278 (25 August 1999) 相似文献
10.
The catalogue of negative ions in superfluid helium has been extended using the example of Ar−, Kr−, and Xe−. Such objects cannot exist in vacuum, since the polarization attraction of an electron to the inert A atom is insufficient
for the formation of the bound state A−. However, these objects exist in helium as stable or metastable with a very long lifetime. The effect is due to the electron
localization in liquid helium. If a mixture of excited A* atoms and electrons is prepared in the gas phase above liquid helium,
the reaction A* + e = A*− becomes possible for all atoms of the periodic table. Such charges can be immersed into liquid helium by the electric field.
In this case, the radiative decay A*− = A + e allowed in vacuum can be forbidden in liquid. This leads to the formation of the new unique objects A−, which can exist in liquid helium but are absent in nature. The size of such charged formations has been determined and is
close the radius of a usual electron bubble in helium. 相似文献
11.
A method for obtaining finite electronic systems on a liquid-helium surface is proposed. If a thin film of liquid helium lies
above a bottom capacitor plate made in the form of metal rings connected with one another, then electrons will accumulate
in potential troughs near these rings. The purity of the helium surface, i.e., the absence of impurities and pinning centers
on it, affords an excellent opportunity for investigating the Aharonov-Bohm effect in an ideal ring of a Wigner crystal and
a Luttinger liquid
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 6, 410–414 (25 March 1998) 相似文献
12.
The problem of the equilibrium form of a charged surface of a dielectric liquid in a strong electric field, such that a flat
surface becomes unstable, is studied. A periodic long-wavelength structure with a small amplitude can arise when the gap between
the surface and a charged electrode is small compared with the capillary length and the charge completely screens the electric
field. The equilibrium form of the surface is calculated assuming that the resulting wave is one-dimensional. The effect of
the boundary conditions at the vessel walls on the dependence of the amplitude of the standing wave on the applied voltage
is estimated. It is shown that this dependence is very sensitive to the conditions of contact between the vessel walls and
the liquid. The possibility is discussed of using the theory developed in this paper to explain the experimental results obtained
with a charged liquid-hydrogen surface.
Zh. éksp. Teor. Fiz. 115, 43–49 (January 1999) 相似文献
13.
It is shown that the critical self-charge for the onset of instability of a charged drop in a flow of an ideal fluid decreases
as the flow velocity of the fluid past the drop increases, i.e., a complex instability arises which is a superposition of
the instabilities of the free surface of the drop with respect to the tangential discontinuity of the velocity field at the
free surface of the drop and with respect to the self-charge.
Zh. Tekh. Fiz. 69, 7–14 (May 1999) 相似文献
14.
V. V. Ivanov T. V. Rakhimova A. O. Serov N. V. Suetin A. F. Pal’ 《Journal of Experimental and Theoretical Physics》1999,88(6):1105-1114
Elementary processes in dusty, beam-driven plasma discharges are studied experimentally and theoretically for the first time.
A theoretical model is constructed for a beam-driven plasma containing macroscopic particles. The effect of macroscopic particles
on the electron energy distribution function is estimated assuming a Coulomb field for the particles. The resulting rate of
electron-ion recombination on the macroscopic particles is compared with the electron loss constant calculated from the electron
energy distribution function with an electron absorption constant in the orbital-motion approximation. This approximation,
which is valid in the collisionless case, is found to work satisfactorily beyond its range of applicability. The distributions
of the charged particles and electric fields created by macroscopic particles in a helium plasma are determined. The experimental
data demonstrate the importance of secondary emission by high-energy electrons.
Zh. éksp. Teor. Fiz. 115, 2020–2036 (June 1999) 相似文献
15.
P. D. Grigor’ev 《JETP Letters》1997,66(9):630-636
The energies and widths of the levels of an electron on impurity centers on the surface of liquid helium are calculated with
allowance for the deformation of the surface. The level shift associated with the deformation effects is small and decreases
very slowly with increasing level number. However, even a small shift of the energy levels relative to one another affects
ripplon scattering, which makes the main contribution to the level width at low temperatures. It is predicted theoretically
that this width depends very strongly on the external parameters and on the level number and that a maximum obtains at a clamping
field E
⊥=51500 V/cm. The width of the levels of an electron in a bound state is found to be less than for free electrons. This makes
it possible to perform a beautiful spectroscopic experiment.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 9, 599–604 (10 November 1997) 相似文献
16.
Electron cyclotron resonance (ECR) plasma breakdown is studied in a small linear cylindrical system with four different gases
— hydrogen, helium, argon and nitrogen. Microwave power in the experimental system is delivered by a magnetron at 2.45 ± 0.02
GHz in TE10 mode and launched radially to have extra-ordinary (X) wave in plasma. The axial magnetic field required for ECR in the system
is such that the fundamental ECR surface (B = 875.0 G) resides at the geometrical centre of the plasma system. ECR breakdown parameters such as plasma delay time and
plasma decay time from plasma density measurements are carried out at the centre using a Langmuir probe. The operating parameters
such as working gas pressure (1 × 10−5−1× 10−2 mbar) and input microwave power (160–800 W) are varied and the corresponding effect on the breakdown parameters is studied.
The experimental results obtained are presented in this paper.
相似文献
17.
E. Scifoni F.A. Gianturco 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(3):323-333
Experimental and theoretical studies in large ionic helium clusters have suggested the presence of a diatomic (and occasionally triatomic) charged molecular core surrounded by the other atoms which are bound to it by weaker interactions [1-3]. The understanding of the interactions between the system He 2 + and an additional He atom of the cluster is therefore important in order to start modelling the full cluster interaction potential. In the present work we carry out a new set of calculations on the full potential and on the bound states supported by the He 2 + isolated ion and further extend them to generate a Rigid Rotor (RR) potential energy surface (PES) for the triatomic system with He 2 + kept at its equilibrium geometry (2.0 a.u.). The 13 bound states which were found and the overall angular anisotropy that exists for this Potential Energy Surface (PES) are discussed in detail. We additionally show results of calculations on the surface vibrational extension to nine different values of the He 2 + interatomic distance, thereby generating a fuller, three-dimensional interaction potential. A simpler modelling of the latter via “Pseudo Rigid Rotor” calculations for the bound states with a vibrationally excited core is also presented and discussed. 相似文献
18.
The implications of magnetic translations for internal optical transitions of charged mobile electron-hole (e-h) complexes and ions in a uniform magnetic field B are discussed. It is shown that transitions of such complexes are governed by a novel exact selection rule. Internal intraband
transitions of two-dimensional (2D) charged excitons X
− in strong magnetic fields are considered as an illustrative example.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 8, 504–509 (25 October 1999)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
19.
Thermal desorption of helium from presaturated crystals was used for mass spectrometric investigations of the diffusion and
solubility of helium in lead fluoride crystals in the temperature range 606–714K which precedes the transition of the crystal
to the superionic state. The experimental apparatus and measurement method are described and mechanisms for the diffusion
and solubility of helium in PbF2 are discussed.
Zh. Tekh. Fiz. 68, 85–89 (December 1998) 相似文献
20.
B. A. Saranin 《Technical Physics》1999,44(12):1407-1412
The electric field at the surface of two conducting spherical charged particles and their interaction force are calculated.
It is shown that as particles carrying like charge approach each other, the force changes sign and becomes attractive. The
case where the charge on each particle varies as the square of its radius is an exception (repulsion at any distance between
the particles). Self-similar asymptotic solutions for the interaction force and energy are found for particles of identical
size. For a pair of charged water drops falling simultaneously in the atmosphere, a numerical simulation shows that a drop
formed by coalescence of the pair may be subject to the Rayleigh instability.
Zh. Tekh. Fiz. 69, 12–17 (December 1999) 相似文献