共查询到20条相似文献,搜索用时 15 毫秒
1.
V. E. Fortov A. P. Nefedov O. F. Petrov A. A. Samaryan A. V. Chernyshev 《Journal of Experimental and Theoretical Physics》1997,84(2):256-261
The formation of spatially ordered CeO2 particle structures in a thermal plasma at atmospheric pressure and temperatures of 1700–2200 K is studied. The spatial structure
of the particles in the plasma is analyzed using laser time-of-flight counting of individual particles. Probe and optical
diagnostics are used to determine the parameters of the thermal plasma. The CeO2 particles were positively charged (about 103 electronic charges). The resulting Coulomb interaction parameter for the particles is γ
p>120, which corresponds to a highly nonideal plasma.
Zh. éksp. Teor. Fiz. 111, 467–477 (February 1997) 相似文献
2.
A. S. Ioselevich 《JETP Letters》2010,91(1):40-47
A granular system slightly below the percolation threshold is a collection of finite metallic clusters, characterized by wide
spectrum of sizes, resistances, and charging energies. Electrons hop from cluster to clusters via short insulating “links”
of high resistance. At low temperatures all clusters are Coulomb blockaded and the dc-conductivity σ is exponentially suppressed.
At lowest T the leading transport mechanism is variable range cotunneling via largest (critical) clusters, leading to the modified Efros-Shklovsky
law. At intermediate temperatures the principal suppression of ρ originates from the Coulomb zero bias anomaly occurring,
when electron tunnels between adjacent large clusters with large resistances. Such clusters are essentially extended objects
and their internal dynamics should be taken into account. In this regime the T-dependence of ρ is stretched exponential with a nontrivial index, expressed through the indices of percolation theory. Due
to the fractal structure of large clusters the anomaly is strongly enhanced: it arises not only in low dimensions, but also
in d = 3 case. 相似文献
3.
An analytic expression of the potential energy surface (PES) of the ground state of the Ne-HF complex is obtained by utilizing
nonlinear least square method to fit the intermolecular interaction energies [Zhang Y. Guizhou Science, 2003, 21(3): 9–13 (in Chinese)], which have been computed using the augmented correlation-consistent polarized quadruple
zeta basis set aug-cc-pVQZ at the theoretical level of CCSD (T). On the basis of the PES, the partial cross sections (PCSs)
at the incident energies of 60, 75, 100 and 150 meV for collisions between Ne atoms and HF molecules are calculated using
the quantum close coupling approach. The effects of the long-range attractive and the short-range anisotropic interactions
on the inelastic PCSs are discussed in detail. The results show: (1) The long-range attractive well of the EPS makes the significant
contribution to the lower excitation PCSs, especially the tail maximum for j = 0→j′ = 1 transitions, whereas no contribution is to the j′⩾3 inelastic transitions. (2) The short-range (the repulsive and attractive) interaction makes the significant contribution
to the lower excitation PCSs, especially the main peak for j = 0→j′ = 1, 2. As for the transitions of j′⩾3, the short-range interaction plays a key role in the inelastic excitation. (3) Although the positions of the maximums
and minimums of the inelastic PCSs are different at the collision energies, they correspond to almost the same impact parameter.
Supported by the National Natural Science Foundation of China (Grant Nos. 10676025 and 10574096) 相似文献
4.
V. F. Gantmakher 《JETP Letters》2011,94(8):626-628
It has been shown that the observed correlation between the resistivity ρ of high-resistivity metallic alloys and the sign
of the temperature derivative of their resistivity can be explained by taking into account the weak localization effect. This
correlation is as follows: the derivative dρ/dT is negative for alloys with resistivity in the range of 150–300 μΩ cm, which corresponds to the mean free path of electrons
about the interatomic distance; however, this derivative is positive for alloys with lower resistivities (Mooij rule). 相似文献
5.
We study the energy spectrum of the impurity states in tunnel-coupled double quantum wells for Coulomb and short-range donor
potentials. We calculate the impurity contribution and the density of states and detect the transformation of a localized
donor state into a resonant state when the binding energy of the donor in an isolated quantum well is less than the separation
of the energy levels of the double quantum wells. In the opposite case, where the binding energy is greater than the level
separation, there is tunneling repulsion between adjacent impurity levels, with the degree of degeneracy of the levels changing
when there is tunneling mixing of the ground and excited impurity states from different wells. Resonant states emerge in an
asymmetric double quantum well, while in a symmetric double quantum well the impurity level at the barrier’s center proves
to be localized even against the background of the continuum. The calculations are based on a general expression for the impurity
contribution to the density of states in terms of a 2-by-2 matrix Green’s function, i.e., only a pair of tunnel-coupled levels
of the double quantum wells is taken into account. For an impurity with a short-range potential, we derive a matrix generalization
of the Koster-Slater solution, while the impurity with a Coulomb potential is analyzed by using the approximation of a narrow
resonance and close arrangement of the repulsive levels.
Zh. éksp. Teor. Fiz. 115, 1337–1352 (April 1999) 相似文献
6.
A. A. Valuev A. S. Kaklyugin G. É. Norman 《Journal of Experimental and Theoretical Physics》1998,86(3):480-488
This paper shows how the concepts commonly used for a Debye plasma—Landau damping, collisional damping, short-range and long-range
collisions, and plasma waves—must be revised to describe a nonideal electron-ion plasma. The degrees of freedom of a nonideal
plasma are divided into collective and individual. The increase and saturation of the fraction of collective degrees of freedom
as the coupling constant increases is discussed. The Tatarskii approach for a system of coupled oscillators makes it possible
to model the collective degrees of freedom of a nonideal plasma by a set of Langevin oscillators in a thermostat. The correlation
energy and the energy of the plasma waves are found. The concepts developed here made it possible to determine the dispersion
of the plasma waves and their damping. The effect of damping on the discrepancy between the position of the maximum of the
dynamic structure factor and the real part of the solution of the dispersion equation is considered. The effective collision
frequency of the individual degrees of freedom (the electrons) is estimated, taking into account both short-range pairwise
scattering and scattering at plasma waves.
Zh. éksp. Teor. Fiz. 113, 880–896 (March 1998) 相似文献
7.
Analytical expressions are obtained for the ionization potentials of neutral atoms and ions in the screened Coulomb potential
of a nonideal plasma. Among all the chemical elements considered, cesium exhibits the greatest relative lowering of the ionization
potentials in comparison with the case of an unscreened interaction.
Zh. Tekh. Fiz. 68, 45–50 (June 1998) 相似文献
8.
The spectral reflectivity ρ in the region 0.36–2.1 μm and its change Δρ with irradiation by 30 keV electrons versus the average
grain sizer
av in a TiO2 (rutile) powder has been studied in the range 1–7.5 μm. It has been established that the dependence of ρ onr
av differs for different regions of the spectrum, but there is a common increase of ρ in the size range 2.5–4 μm. The value
of Δρ after irradiation is also less in powders with this range of sizes. It has been shown that the dependence Δρ=f(r
av) with increasing electron fluence from 2·1015 to 4·1016 is strengthened for one band and weakened for another.
Tomsk Polytechnic University, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 41, No. 12, pp.
52–58, December, 1998. 相似文献
9.
A. G. Lipson B. F. Lyakov D. M. Sakov V. A. Kuznetsov 《Physics of the Solid State》1997,39(12):1891-1894
An increase has been found in the electrical conductivity of electrochemically dehydrogenated palladium hydrides (deuterides)
as compared with original samples of pure palladium in a wide temperature range (75–300 K). It is shown that this effect is
due to the suppression of the scattering of conduction electrons by phonons in the palladium lattice for T⩾θ (θ is the Debye temperature) in the presence of clusters of quasimetallic hydrogen (deuterium).
Fiz. Tverd. Tela (St. Petersburg) 39, 2113–2117 (December 1997) 相似文献
10.
M. D. Volnyanskii S. N. Plyaka M. P. Trubitsyn Yahia A. H. Obaidat 《Physics of the Solid State》2012,54(3):499-503
The electrical properties of a lithium heptagermanate (Li2Ge7O15) crystal have been studied in DC and AC measuring fields at temperatures from 500 to 700 K. In a DC field, a substantial
decrease of electrical conductivity σ with time has been detected. On the basis of kinetic dependences σ(t), estimates of the charge carrier diffusion coefficient D have been obtained. In the frequency range 101–105 Hz, the spectra of complex impedance ρ*(f) have been measured. The analysis of diagrams in the complex plane (ρ″–ρ′) has been performed within the equivalent circuit
approach. It has been shown that, in the considered temperature and frequency intervals, the electrical properties of Li2Ge7O15 crystals have been determined by the hopping conduction of interstitial lithium ions A
Li and accumulation of charge carriers near the blocking Pt electrodes. 相似文献
11.
Gamzatov A. G. Batdalov A. B. Khanov L. N. Mankevich A. S. Korsakov I. E. Kaul’ A. R. 《Physics of the Solid State》2012,54(3):617-621
Results of investigation of resistivity and magnetoresistance of manganites La1 − x
K
x
MnO3 (x = 0.050–0.175) are presented. Behavior of resistivity ρ(T) in the paramagnetic and ferromagnetic phases has been described. To describe ρ(T) near the phase-transition temperature, notions of the percolation theory have been used. Two maxima have been found in the
dependence ρ(T); their appearance has been attributed to the ceramic nature of the studied samples. The observed increase in magnetoresistance
with a decrease in temperature is caused by intergranular spin-polarized tunneling of charge carriers. 相似文献
12.
S C Phatak 《Pramana》1982,18(2):175-198
The real and imaginary parts of pion-nucleus optical potential arising from pion absorption channel have been computed. A
two-nucleon model of pion absorption which includesπ andρ rescattering andS-wave interaction has been used. The effects of short-range nucleon-nucleon correlations, Pauli blocking and formfactors have
been included. The threshold values of imaginary absorption potential are reasonably close to density-squared terms of phenomenological
potentials. The real part ofP-wave potential is attractive and that ofS-wave potential is weakly attractive at lower pion energies and changes sign as pion energy is increased. The calculation
shows that the real part of absorption is significantly affected by short-range correlations and Pauli-blocking. 相似文献
13.
Sineeba Ramadas Vishnu M. Bannur 《The European Physical Journal C - Particles and Fields》2012,72(4):1975
From an analogy with non-relativistic degenerate QED plasma we make an estimate of the coupling strength of QGP hypothesized
to be present in compact star interiors. At densities ranging from 3ρ
0–10ρ
0 (normal nuclear density ρ
0=0.16 fm−3), quark matter is found to be strongly to intermediately coupled. The equation of state for QED plasma obtained via Pade
approximation, modified to QGP, yields stable stellar sequences with maximum mass ≳2M
⊙ for B
1/4≲215 MeV. 相似文献
14.
A. E. Kar’kin D. A. Shulyatev A. A. Arsenov V. A. Cherepanov E. A. Filonova 《Journal of Experimental and Theoretical Physics》1999,89(2):358-365
A comparative study of the longitudinal ρ
xx
and transverse ρ
xy
resistivities and magnetic susceptibility χ
ac of La0.8Sr0.2MnO3 single crystals and ceramic samples has been conducted in a wide range of temperatures T=1.7–370 K and magnetic fields, H=0–13.6 T. It turned out that the relation ρ
xy
∼ρ
xx
, which is expected to hold in the case of carrier scattering by magnetic fluctuations, applies to the single crystals. In
polycrystals, an additional H-dependent contribution to the resistivity tentatively attributed to plane (near grain boundaries) and bulk “defects” of the
magnetic sublattice has been detected. The scattering of carriers by these defects does not make a notable contribution to
the anomalous Hall effect and magnetic susceptibility χ
ac. As a result, the curve of ρ
xy
versus ρ
xx
seems to be steeper than a linear dependence. Under the assumption that the materials under investigation are metals with
constant carrier concentrations, the conductivity σ=1/ρ
xx
due to the critical magnetic scattering calculated in the molecular field approximation reproduces the main features of experimental
data, namely, the drop in the amplitude and shift of the resistivity peak near the Curie point with increasing magnetic field
H and also a relatively slow change in the derivative dσ/dH with increasing temperature in the region T⩽T
C
. The large hole concentration of about two per unit cell derived from Hall measurements indicates that carriers of opposite
signs can coexist in these materials.
Zh. éksp. Teor. Fiz. 116, 671–683 (August 1999) 相似文献
15.
V. E. Fortov V. Ya. Ternovoi S. V. Kvitov V. B. Mintsev D. N. Nikolaev A. A. Pyalling A. S. Filimonov 《JETP Letters》1999,69(12):926-931
The electrical conductivity of a nonideal hydrogen plasma is measured under shock-wave compression to pressures ∼1.5 Mbar.
It is found that the conductivity increases sharply (by five orders of magnitude) at a density ρ∼0.3−0.4 g/cm3, reaching close to liquid-metal values ∼103 S/cm. The data obtained can be described by a nonideal-plasma model taking into account the increase in the number of conduction
electrons as a result of “ionization by pressure.”
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 12, 874–878 (25 June 1999) 相似文献
16.
A. Alastuey V. Ballenegger F. Cornu Ph. A. Martin 《Journal of statistical physics》2008,130(6):1119-1176
We study hydrogen in the Saha regime, within the physical picture in terms of a quantum proton-electron plasma. Long ago,
Saha showed that, at sufficiently low densities and low temperatures, the system behaves almost as an ideal mixture made with
hydrogen atoms in their groundstate, ionized protons and ionized electrons. More recently, that result has been rigorously
proved in some scaling limit where both temperature and density vanish. In that Saha regime, we derive exact low-temperature
expansions for the pressure and internal energy, where density ρ is rescaled in units of a temperature-dependent density ρ
*
which controls the cross-over between full ionization (ρ
≪
ρ
*
) and full atomic recombination (ρ≫ρ
*
). Each term reduces to a function of ρ/ρ
*
times temperature-dependent functions which decay exponentially fast when temperature T vanishes. Scaled expansions are ordered with respect to the corresponding decay rates. Leading terms do reduce to ideal contributions
obtained within Saha theory. We consistently compute all corrections which are exponentially smaller by a factor exp (β
E
H
) at most, where E
H
is the negative groundstate energy of a hydrogen atom and β=1/(k
B
T). They include all effects arising from both the Coulomb potential and the quantum nature of the particles: excitations of
atoms H, formation of molecules H
2, ions H
2+ and H
−, thermal and pressure ionization, plasma polarization, screening, interactions between atoms and ionized charges, etc. Scaled
low-temperature expansions can be viewed as partial resummations of usual virial expansions up to arbitrary high orders in
the density. 相似文献
17.
The weak-field Hall voltage in Si-MOS structures with different mobility is studied on both sides of the metal-insulator transition.
In the vicinity of the critical density on the metallic side of the transition, the Hall voltage is found to deviate by 6–20
% from its classical value. The deviation does not correlate with the strong temperature dependence of the diagonal resistivity
ρ
xx
(T). In particular, the smallest deviation in R
xy
is found in the highest-mobility sample, which exhibits the largest variation in the diagonal resistivity ρ
xx
with temperature.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 1, 48–52 (10 July 1999)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
18.
Galina A. Vergunova Sergey Yu. Gus’kov Vladislav B. Rozanov Olga N. Rozmej 《Journal of Russian Laser Research》2010,31(5):509-518
We investigate theoretically the formation of a plasma in a plane layer of polymer foam (density ρ = 0.002 g/cm3 and thickness 800 μm) under the action of an external source of soft X-ray radiation under the conditions of PHELIX experiments. The incident
flux is assumed to have a Planck’s distribution over the spectrum with T
rad = 20–40 eV. In numerical calculations, the flux of incident X-ray radiation and the spectral constants of the target substance
are varied. The action of an external X-ray radiation source on a low-density foam substance with a density of 2 mg/cm3 causes a plasma to be formed with relatively homogeneous profiles of density and temperature T = 15–35 eV. Absorption of externalradiation energy is distributed in the volume. The plasma temperature increases with increase
in the external energy, and the energy passed through the plasma also increases. The results prove to be sensitive to the
values of optical constants used in numeral simulation. The spectral flux of external radiation passed through the plasma
is chosen as a criterion of correctness of the optical constants used in the calculations. In future experiments using the
PHELIX facility, we plan to investigate the slowing-down of an ion beam in a plasma formed as a result of indirect heating
of low-density polymer triacetate cellulose (TAC) foam with densities ρ = 0.001–0.01 g/cm3 under the action of a pulse of X-ray radiation, into which the laser radiation is preliminarily transformed. 相似文献
19.
An estimate is made for the energy of a virtual atomic structure on the metallic side of the metal-nonmetal transition in
a dense plasma. On the assumption of a nearly uniform valence electron density, the interatomic interaction is treated as
a Madelung energy, which is found to be approximately one-third of that for the one-component plasma model. Our estimate is
verified by solving numerically the pseudowave equation for the valence electrons in ellipsoidal atomic cells which are compatible
with the percolation structure of overlapping classically accessible spheres. The critical value of the Coulomb coupling parameter
has been shown to agree with experiment at the liquid-gas critical points of cesium and rubidium, which can be identified
with the plasma-phase-transition critical points.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 11, 849–854 (10 June 1996)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
20.
L. S. Ewe I. Hamadneh H. Salama N. A. Hamid S. A. Halim R. Abd-Shukor 《Applied Physics A: Materials Science & Processing》2009,95(2):457-463
The magnetotransport and magnetoresistive (MR) properties of manganese-based La0.67Ca0.33MnO3 perovskite with different grain sizes are reported. The electrical resistivity was measured as a function of temperature
in magnetic fields of 0.5 and 1 T. The insulator–metal transition temperature, T
IM, shifted to a higher temperature with the application of the magnetic field. In zero field, T
IM is almost constant (∼271 K) for all samples except for the sample with the largest grain size, where T
IM=265 K. The temperature dependence of resistivity was fitted with several equations in the metallic (ferromagnetic) region
and the insulating (paramagnetic) region. The density of states at the Fermi level, N(E
F), and the activation energy of electron hopping were estimated by fitting the resistivity versus temperature curves. The
ρ–T
2 curves are nearly linear in the metallic regime, but the ρ–T
2.5 curves exhibit a deviation from linearity. The variable range hopping model and small polaron hopping model fit the data
well in the high-temperature region, indicating the existence of the Jahn–Teller distortion that localizes the charge carriers.
MR was found to increase with an increase in the magnetic field, an effect which is attributed to the intergrain spin tunneling
effect. 相似文献