共查询到20条相似文献,搜索用时 109 毫秒
1.
The cyclotron resonance of inversion-layer electrons on (100)p-type Si is found to depend sensitively on an externally applied compressive stress. At low temperatures (T ? 10 K) we observe a considerable increase of the cyclotron mass m1c with stress S along the [001] direction. The effect is most strongly observed at low electron densities ns. For and ns~2 × 1011cm-2 we obtain instead of the expected 0.2m0. Along with this change of a strong narrowing of the resonance is noted. Raising the temperature gives an additional ns- dependent increase of . 相似文献
2.
We consider semi-inclusive reactions of the type p + p → (particle with large pT) + n charged particles + neutrals, and propose the following scaling law for the distribution function of the large-pT particle produced in association with n charged particles. This scaling rule is shown to be consistent with present information on single-particle spectra and average associated multiplicities at large pT. Also, we show that if the associated multiplicity were to continue to increase linearly with pT, then moments of the multiplicity distribution would increase like powers of s. 相似文献
3.
The mobility μ of a very pure semiconductor at very low temperatures is investigated in terms of a model where electrons are scattered by charged impurities distributed uniformly in space, and the electron-electron interaction is taken into account by the Debye-Hueckel screening in the interaction potential. The equation for the current relaxation rate Γ, derived previously by the proper connected diagram expansion, incorporates the quasi-particle effect in a self-consistent manner. The solution of this equation at high carrier concentrations n yields the so-called Brooks-Herring formula. At lower concentrations, the solution deviates significantly from the latter. The solution is in general smaller than the standard expression for the rate based on the Boltzmann equation; and this is consistent with the existing conductivity data available. At the very low concentrations e.g. n = n3 = 1013cm?3 or lower for Ge, the mobility calculated is inversely proportional to the square-root of the impurity concentration ns, and has a -dependence (T: temperature). , where k is the dielectric constant. The conductivity data directly comparable with this formula are not available at present. However, the quasi-particle effect which led to this peculiar concentration-dependence should also show itself in the cyclotron resonance width; there, experiment and theory both show the -dependence for very pure semiconductors. 相似文献
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The predictions of perturbative QCD are derived in the deep euclidean region, whereas the physical region for most observables is timelike. The confrontation of these predictions with experiment thus necessitates an analytic continuation. This we find introduces large higher order corrections in terms of αs(|Q2|), the usual choice ofperturbative expansion parameter. These corrections are naturally absorbed by changing to the expansion parameter , where αs(Q2)n is the leading term in the spacelike region. For the intermediate range of Q2 experimentally accessible at present, where is significantly smaller than αs(|Q2|), we find the resulting phenomenology is improved. In particular, we demonstrate how the values of obtained from analyses of quarkonium decays become consistent. 相似文献
6.
The low temperature mobility μ limited by charged impurities is calculated by solving the equation for the relaxation rate previously derived. The calculated μ behaves like In for lowest concentrations ns<1011cm?3 for Ge and for intermediate concentrations ns ~ 1012?1014cm?3. 相似文献
7.
A model for large p⊥ production, yielding three different scaling relations in different regions of s and p⊥ is presented. The couplings may be chosen such that scaling is valid at present energies while at higher energies scaling should manifest itself. 相似文献
8.
Charalampos A. Kolassis 《Physics letters. A》1983,95(2):82-84
We consider a neutrino field with geodesic rays in interaction with a gravitational field admitting a Killing vector field nμ. It is found that for solutions of the Einstein-Weyl field equations the neutrino field ξA and the neutrino flux vector lμ are restricted by the equations: and , whereas s is a real constant. In the case of pure radiation neutrino fields these equations become: , , where p and s are in general real functions of the coordinates. 相似文献
9.
B. Ghidini F. Navach A. Palano V. Picciarelli G. Zito J. Bröring K. Müller E. Paul W. Renneberg W. Rühmer J. Eades B. French L. Mandelli J. Moebes M.E. Edwards I. Smith R.A. Donald C. Palazzi-Cerrina 《Nuclear Physics B》1978,132(5):429-438
The reaction , where ps is a slow proton, was measured at 12 GeV/c incident momentum with the CERN-OMEGA spectrometer. Both antiproton and proton were identified uniquely by electronics information. We obtained 1844 events with four-momentum Transfer squared in the range 0.13 ? |t| ? 0.33 GeV2 and with invariant masses up to 2.5 GeV. The corresponding cross section in this t range is determined to be σ = 4 ± 0.4 μb. Extrapolating the differential cross section over the whole t range assuming dσ/dt ≈ exp(5.3t) we estimate a cross section of σ = 9.3 ± 2.0 μb. Comparison with data on (where ns is a slow neutron) in the same t range shows that the cross sections have approximately the same magnitude. 相似文献
10.
t-channel unitarity equations are derived for n-particle overlap functions. Together with s-channel unitarity they lead to scaling laws for the inelastic s-channel partial-wave amplitudes in the limits . Assuming the validity of the scaling law in the whole range, allowed by s-channel unitarity — i.e. for we obtain constant production cross sections σ(n)(s) at high energies s → ∞ up to s factors. 相似文献
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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
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C. Defoix L. Dobrzynski P. Espigat M. Laloum P.Ladrón de Guevara C. Angelini A. Bigi R. Casali R. Pazzi 《Nuclear Physics B》1980,162(1):12-40
An experimental analysis of interactions between the p threshold (√s = 1878 MeV) and √s = 2 100 MeV leads to clear evidence for an s-channel effect in the reaction . A comparison is made with the backward elastic scattering and charge-exchange behaviour. An interpretation in terms of an object strongly coupled to mesonic decay modes, with small or middle-sized elasticity (x ? 0.135?0.06+0.13) is given. No significant narrow structure is observed in the backward elastic scattering between 1.9 and 2 GeV. The experimental resolution of √s in this case is 2 MeV. 相似文献
15.
y.И. caфpoнoвa 《Journal of Quantitative Spectroscopy & Radiative Transfer》1975,15(3):231-242
Energies and dipole matrix elements have been calculated for He, Li, Be, B, C, N, O, F, and Ne-like ions (configurations 1s22sn12pn2?1s22sn1?12pn2+1). The Hartree-Fock energy, the correlation energy, and relativistic corrections were taken into account. Relativistic corrections were obtained by computing the entire quantity HB. Numerical results are presented for energies of the terms in the form , and for the fine structure of the terms in the form . Dipole matrix elements are required for calculation of oscillator strengths or transition probabilities. For the dipole matrix elements, two terms of the expansion in have been obtained. Numerical results are presented in the form P(a, a′) = (a/Z)[1 + (τ/Z)]. 相似文献
16.
S. Fujita 《Solid State Communications》1975,17(8):915-917
The low temperature mobility μ limited by charged impurities in very pure semiconductors (Ge) is interpreted in terms of the Coulomb collision in medium. The theory yields a peculiar dependence in temperature T and charged impurity concentration . 相似文献
17.
Metastable He2 molecules are produced by a dc discharge in a flowing He stream. Laser excitation downstream of the discharge produces excitation spectra for a number of He2 states. LIF spectra are observed for the series for n = 4–9, excepting 5 and the series for n = 5–15. 相似文献
18.
Based on the proper connected diagram expansion, we calculated cyclotron resonance widths Γn associated with neighboring Landau states (n, n +1) for free electrons in interaction with more than one kind of impurities. In 3D usual Matthiessen's rule Γn=Γ(1)n+Γ(2)n+…where Γ(i)n represent widths calculated separately for each kind, is obtained. In 2D a new rule: is obtained. 相似文献
19.
H. Albrecht U. Binder G. Harder A. Philipp W. Schmidt-Parzefall H. Schröder H.D. Schulz R. Wurth A. Drescher B. Gräwe U. Matthiesen H. Scheck J. Spengler D. Wegener K.R. Schubert J. Stiewe R. Waldi H. Gennow 《Physics letters. [Part B]》1985,158(6):525-530
Using the ARGUS detector at DORIS II, we have observed a signal of 36.7±8.0 events in the decay channel D0→Ks0φ. In the same data sample, we have observed the well established decay D0→Ks0π+π?, and find the ratio, , to be 0.186±0.052. The substantial value of (0.99±0.32±0.17)% then derived for the branching ratio for gives direct evidence that W exchange contributes D0 decay. 相似文献
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