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1.
The usual condition for static balance, for two bodies with masses and charges mi and ei (i = 1, 2), is . From a post-Newtonian analysis of the two-body problem, an alternate condition for static balance has been found. We do not know if this condition is exact beyond the post-Newtonian approximation. 相似文献
2.
T. Sone 《Solid State Communications》1984,52(3):325-327
The concentration dependence of the magnetic susceptibility for the system of randomly distributed dilute magnetic impurities in a d-dimensional metal or on a metal surface is studied at zero-temperature under the mean-random-field approximation. It is shown that, if the amplitude of the RKKY-type interaction between the magnetic impurities behaves like at a large distance r, the susceptibility is proportional to , where c is the concentration of the magnetic impurities. 相似文献
3.
Dependence of static dielectric susceptibility and correlation length of charge density waves (CDW) with weak defects on parameter of incommensurability with lattice is investigated. In almost commensurate phase (h?hchc), and Rc ~ (h ? hc). In. Far from commensurability , , where a is the dimensionless ratio of random potential intensities, corresponding to backward and forward scattering impurities. 相似文献
4.
Electron and hole-drift velocity is measured in the layer semiconductors HgI2, GaSe, PbI2 and GaS, mainly on the direction parallel to the c-axis between 80 and 400 K. In the electric field range in question, electron and hole-drift velocity is proportional to the field except in the case of GaS, where a superohmic behaviour is observed. At 300 K the mobility parallel to the c-axis is , for HgI2; , for GaSe; , for PbI2. The highest hole mobility observed in GaS is .Where it is possible to compare these data with mobility values perpendicular to the c-axis, the three-dimensional character of the energy bands near the fundamental gap is proved.For HgI2 and GaSe we find no evidence for the large anisotropy of charge-carrier transport properties usually attributed to layered semiconductors. The mobility-temperature dependences found are interpreted on the basis of polar and non-polar optical phonon scattering mechanisms, except in the case of GaS, where a trapping model is used. The effective masses of electrons and holes are reported for PbI2 and, for the first time, for HgI2. 相似文献
5.
We calculate the effective electron-hole interaction Vre in the presence of an exciton gas, which reads in real space: The parameters Ci and Zi are given explicitly for GaAs. For this material, we show the binding energy of the exciton is weakly modified so long as . (R0, exciton Rydberg, a0 exciyon radius, ?ex exciton density, T temperature). 相似文献
6.
M. Pelizzone B. Lachal H.W. Meul A. Treyvaud J. Muller A. Perrin 《Journal of magnetism and magnetic materials》1984,42(2):167-172
The magnetic susceptibility, magnetization, specific heat and electrical resistivity were measured on the new material Tl2Fe6Te6. All the data show a very sharp anomaly revealing a phase transition to ferromagnetism at Tc≈220 K. The presence in the structure of one-dimensional metallic clusters is evidenced by a very strong magnetic anisotropy in the ferromagnetic state, showing an interesting intermediate situation between a pure linear chain and 3-dimensional iron. Furthermore, the unusual sharpness of the transition leads us to anticipate a first-order phase transformation, but the lack of detectable thermal hysteresis was surprising. The molecular field model proposed by Bean and Rodbell in order to account for the similar behavior of MnAs gives a close representation of our magnetic data. Thus, a pronounced dependence of the exchange interaction upon interatomic spacing may well be the dominant mechanism leading to the observed phenomena. 相似文献
7.
Richard L. Liboff 《Journal of Physics and Chemistry of Solids》1985,46(11):1327-1330
A quasiclassical formulation for mobility in extrinsic semiconductors is presented based on scattering from ionized impurity atoms. Quantum theory enters the otherwise classical Chapman-Enskog expansion of the Boltzmann equation through incorporation of the Thomas-Fermi interaction potential together with the Bom approximation for evaluation of scattering integrals. The following expression results for mobility μi, (cgs): , , where ns is impurity concentration, m1 is effective mass, E1(γ) is the exponential integral, ? is dielectric constant and γ is dimensionless Thomas-Fermi energy. The structure of the dimensional factor in the preceding expression for μi agrees with previous expressions for this parameter. 相似文献
8.
An analysis of dynamic and nonlocal longitudinal dielectric response properties of a two-dimensional Landau-quantized plasma is carried out, using a thermodynamic Green's function formulation of the RPA with a two-dimensional thermal Green's function for electron propagation in a magnetic field developed in closed form. The longitudinal-electrostatic plasmon dispersion relation is discussed in the low wavenumber regime with nonlocal corrections, and Bernstein mode structure is studied for arbitrary wavenumber. All regimes of magnetic field strength and statistics are investigated. The class of integrals treated here should have broad applicability in other two-dimensional and finite slab plasma studies.The two-dimensional static shielding law in a magnetic field is analyzed for low wavenumber, and for large distances we find . The inverse screening length (? = density, ξ = chemical potential) is evaluated in all regimes of magnetic field strength and all statistical regimes. k0 exhibits violent DHVA oscillatory behavior in the degenerate zero-temperature case at higher field strengths, and the shielding is complete when , but there is no shielding when . A careful analysis confirms that there is no shielding at large distances in the degenerate quantum strong field limit . Since shielding does persist in the nondegenerate quantum strong field limit , there should be a pronounced change in physical properties that depend on shielding if the system is driven through a high field statistical transition. (It should be noted that the static shielding law of semiclassical and classical models has no dependence on magnetic field in two dimensions, as in three dimensions.) Finally, we find that the zero field two-dimensional Freidel-Kohn “wiggle” static shielding phenomenon is destroyed by the dispersal of the zero field continuum of electron states into the discrete set of Landau-quantized orbitals due to the imposition of the magnetic field. 相似文献
9.
It is proved that the quantum mechanical Hamiltonian for bosons (resp, fermions) is bounded from below if N ≤ cbκ?1 (resp. ). H is unbounded from below if N ≥ cblκ?1 (resp. ). The constants cb and cbl (resp. cf and cfl) differ by about a factor 2 (resp. 4). 相似文献
10.
The 0-0, 1-1, 2-2, and 3-3 bands of the A2Π-X2Σ+ transition of the tritiated beryllium monohydride molecule have been observed at 5000 Å in emission using a beryllium hollow-cathode discharge in a He + T2 mixture. The rotational analysis of these bands yields the following principal molecular constants. From the pure electronic energy difference (EΠ - EΣ)BeT = 20 037.91 ± 1.5 cm?1 and the corresponding previously known values for BeH and BeD, the following electronic isotope shifts are derived and related to the theoretical approach given by Bunker to the problem of the breakdown of the Born-Oppenheimer approximation. 相似文献
11.
The influence of self-fields on the equilibrium and stability properties of relativistic beam-plasma systems is studied within the framework of the Vlasov-Maxwell equations. The analysis is carried out in linear geometry, where the relativistic electron beam propagates through a background plasma (assumed nonrelativistic) along a uniform guide field , It is assumed that for the beam electrons (ν is Budker's parameter, and γ0mc2 is the electron energy), but no a priori assumption is made that the beam density is small (or large) in comparison with the plasma density, or that conditions of charge neutrality or current neutrality prevail in equilibrium. It is shown that the equilibrium self-electric and self-magnetic fields, and , can have a large effect on equilibrium and stability behavior. Equilibrium properties are calculated for beam (j = b) and plasma (j = e, i) distribution functions of the form fb0(H, Pθ, Pz) = F(H ? ωrbPθ) × δ(Pz ? P0)(j = b), and (j = e, i), where H is the energy, Pθ is the canonical angular momentum, Pz is the axial canonical momentum, and ωrj (the angular velocity of mean rotation for j = b, e, i), Vj (the mean axial velocity for j = e, i), and P0 are constants. The linearized Vlasov-Maxwell equations are then used to investigate stability properties in circumstances where the equilibrium densities of the various components (j = b, e, i) are approximately constant. The corresponding electrostatic dispersion relation and ordinary-mode electromagnetic dispersion relation are derived (including self-field effects) for body-wave perturbations localized to the beam interior (r <Rb). These dispersion relations are analyzed in the limit of a cold beam and cold plasma background, to illustrate the basic effect that lack of charge neutrality and/or current neutrality can have on the two-stream and filamentation instabilities. It is shown that relative rotation (induced by self-fields) between the various components (j = b, e, i) can (a) result in modified two-stream instability for propagation nearly perpendicular to , and (b) significantly extend the band of unstable kz-values for axial two-stream instability. Moreover, in circumstances where the beam-plasma system is charge-neutralized but not current-neutralized, it is shown that the azimuthal self-magnetic field has a stabilizing influence on the filamentation instability for ordinary-mode propagation perpendicular to . 相似文献
12.
Although is forbidden in near case c molecules the A′ ← X transition can be efficiently accomplished by the three-step sequence . Transitions to a range of levels of A′, vA′ = 2–38, have been recorded by this means, using J-selective polarization-labeling spectroscopy. Principal constants of the A′ state of I35Cl are Te = 12682.05, ωe = 224.57, ωeχe = 1.882, ωeye = ?0.0107, Be = 0.08653, and αe = 0.000675 cm?1. The A′ state is therefore similar in its physical characteristics to two other (relatively) deep states, and , of the 2431 configuration. 相似文献
13.
A weak emission spectrum of I2 near 2770 Å is reanalyzed and found to to minate on the A(1u3Π) state. The assigned bands span v″ levels 5–19 and v′ levels 0–8. The new assignment is corroborated by isotope shifts, band profile simulations, and Franck-Condon calculations. The excited state is an ion-pair state, probably the 1g state which tends toward . In combination with other results for the A state, the analysis yields the following spectroscopic constants: T″e = 10 907 cm?1, ″e = 1640 cm?1, ω″e = 95 cm?1, ; T′e = 47 559.1 cm?1, ω′e = 106.60 cm?1, . 相似文献
14.
The He2 band systems and are described in detail, and the i and l states characterized. A number of significant perturbations in the i and l states are identified, and the possible perturber states discussed. The following molecular constants (cm?1) are reported:
State | |||||
1707.95 | 35.00 | 7.242g | 0.222 | 1.0782 | |
1703.86 | 34.97 | 7.2264 | 0.2188 | 1.0794 |