共查询到20条相似文献,搜索用时 31 毫秒
1.
A. A. Levchenko G. V. Kolmakov L. P. Mezhov-Deglin V. B. Shikin E. Teske P. Leiderer 《JETP Letters》1997,65(7):572-578
A change in the shape of a charged surface of liquid hydrogen and helium — the formation of a solitary wave (a positively
charged hump for hydrogen and a negatively charged dimple for helium)-is observed in an electric field exceeding a critical
value under conditions of total compensation of the applied field by the surface charge.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 7, 547–552 (10 April 1997) 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 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
4.
V. B. Shikin 《JETP Letters》2002,76(11):660-663
The details of charging a free liquid-helium surface with electrons are discussed. It is shown that the thickness of the helium film varies during this process and gradually decreases under the action of electron pressure on the helium surface. In turn, the pressure depends on the film thickness. Hence, the self-consistent kinetic problem arises with characteristic relaxation time τ mainly of hydrodynamic origin (viscous adjustment of the film thickness to the variable electron pressure). The value of τ is quite sensitive to the film thickness d (τ∝d3). In the most representative interval 10?1 cm>d>10?4 cm, τ varies in the range 10?3s≤τ≤10+8 s. The situation is most intriguing in the vicinity of the critical point (at the critical point, the charged helium film becomes unstable). As it is approached, τ increases to infinity. 相似文献
5.
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
6.
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
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.
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
9.
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
10.
A dispersion relation is proposed and analyzed for the spectrum of capillary motion at a charged flat liquid surface with
allowance made for the finite rate of charge redistribution accompanying equalization of the potential as a result of the
wave deformation of the free surface. It is shown that when the conductivity of the liquid is low, a highly charged surface
becomes unstable as a result of an increase in the amplitude of the aperiodic chargerelaxation motion of the liquid and not
of the wave motion, as is observed for highly conducting media. The finite rate of charge redistribution strongly influences
the structure of the capillary motion spectrum of the liquid and the conditions for the establishment of instability of its
charged surface when the characteristic charge relaxation time is comparable with the characteristic time for equalization
of the wave deformations of the free surface of the liquid.
Zh. Tekh. Fiz. 67, 34–41 (August 1997) 相似文献
11.
S.V. Romanov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,2(3):217-230
In recent experiments performed at the Paul Scherrer Institute (PSI) measurements were made of the yield of the two-photon transition of the fully-ionized muonic boron formed and quenched in a gaseous mixture of diborane B2H6 and helium. In the present work this yield is calculated for an idealized case of a very low diborane density when the main
2
s state decay modes competing with the two-photon transition are due to the electron transfer from helium to the μ-ion. As
the rate of this transfer depends strongly on the relative velocity, a treatment is needed of the whole kinetics of processes
occurring with the μ-ion in helium. Accordingly, within the optical model with a complex potential constructed before we calculate
cross-sections of the elastic scattering and electron transfer. Then the time evolution of the μ-ion energy is considered
and, finally, the yield is calculated. It proves that at helium pressures Torr this yield may be written in the form: ,where the factor C is greater than unity and increases rapidly with the initial energy E0 which the μ-ion has after its formation in the diborane molecule. Thus measurement of the pressure dependence of allows E0 to be estimated. The results obtained make it possible to suggest a similar parametrization of the PSI data.
Received: 21 October 1997 / Revised: 16 January 1998 / Accepted: 2 March 1998 相似文献
12.
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
13.
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
14.
B. Audoin M. Perton N. Chigarev C. Rossignol 《The European physical journal. Special topics》2008,153(1):235-237
Investigation of thin metallic film properties by means
of picosecond ultrasonics [C. Thomsen et al., Phys. Rev. Lett. 53, 989 (1984)] has been under the scope of several studies.
Generation of longitudinal and shear waves [T. Pézeril et al., Phys. Rev. B 73, 132301 (2006); O. Matsuda et al., Phys. Rev. Lett. 93, 095501 (2004)] with a wave vector normal
to the film free surface has been demonstrated. Such measurements cannot
provide complete information about properties of anisotropic films. Extreme
focusing of a laser pump beam (≈0.5 μm) on the sample surface
has recently allowed us to provide evidence of picosecond acoustic
diffraction in thin metallic films (≈1 μm) [C. Rossignol et al., Phys. Rev. Lett. 94, 166106 (2005)]. The resulting
longitudinal and shear wavefronts propagate at group velocity through the
bulk of the film. To interpret the received signals, source directivity
diagrams are calculated taking into account material anisotropy, optical
penetration, and laser beam width on the sample surface. It is shown that
acoustic diffraction increases with optical penetration, so competing with
the increasing of directivity caused by beam width. Reflection with mode
conversion at the film-substrate interface is discussed. 相似文献
15.
On the basis of the longitudinal field Green function, in a three-layer non-symmetrical system of media with spatial dispersion the image-force potential is calculated for surfaces of the semi-infinite helium bath and a liquid helium film, and also for a surface of the phase-separated 3He4He mixture. The dependence of the surface electron spectrum on the film thickness and on the pressing electric field strength is analyzed. 相似文献
16.
采用离子束辅助磁控溅射方法沉积出了纳米晶LaNiAl膜和纳米晶渗氦LaNiAl膜(膜厚约10 m),通过调节Ar-He气氛的比例可控制纳米晶膜中的含氦量(He/LaNiAl的原子分数5.7%~13.8%),通过该方法引入到LaNiAl金属薄膜中的氦量远高于采用球磨法制备的纳米LaNiAl粉中的含氦量。研究结果表明:渗氦LaNiAl膜中的氦含量(原子分数)可达13.9%,氦在膜的深度方向分布均匀;热解析分析恒温条件下沉积的渗氦膜的起始释放温度为848 K,最高释放温度为1407 K,主释放峰为1080 K,初步确定了氦主要是以团簇的形式存在于在纳米晶膜中。 相似文献
17.
Abstract A pseudo-potential technique has been applied to calculate the annihilation rates for positrons in bubbles of helium gas in gold and silver. The positron pseudo-wavefunction in each case was found to be in a surface state of the metal, the exact form of which displayed a slight dependance on the density of the helium gas. The annihilation rate of the positron was the sum of a nearly constant surface rate and a strongly density dependant annihilation rate with the helium electrons. There is a trend for annihilation with the helium to be greater in metals with low free electron densities, the helium in such metals resting closer to the metal surface thus increasing the overlap of the positron wavefunction with the helium. 相似文献
18.
Time-resolved photoluminescence from porous silicon coated with a diamondlike carbon film is investigated. The intensity of
the photoluminescence from the carbon film is obserd to increase after deposition, and there is an accompanying change in
the intensity and a shortwavelength shift of the photoluminescence band of porous silicon that depends on the porosity of
its original layers. These changes are explained by the formation of carbon nanoclusters on the surface of the silicon filaments.
Zh. Tekh. Fiz. 68, 83–87 (April 1998) 相似文献
19.
E. H. Baksht M. I. Lomaev D. V. Rybka D. A. Sorokin V. F. Tarasenko 《Technical Physics》2008,53(12):1560-1564
The parameters of an electron beam generated in helium in the pressure range p = 10−4−12 atm are studied. Nanosecond high-voltage pulses are applied to a gap between a tubular cathode and planar anode, which
is made of 45-μm-thick AlBe foil. Behind the anode, an electron beam is detected at a helium pressure of 12 atm. The pressure
dependence of the beam current amplitude shows three peaks at p ≈ 0.01, ≈ 0.07, and ≈ 3 atm. The beam-induced glow of a luminescent film placed behind the foil and the discharge glow at
different helium pressures in the gas-filled diode are photographed. 相似文献
20.
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