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1.
We have carried out a high-resolution X-ray critical scattering experiment in the isotropic phase connected with the isotropic-smectic-B transition in 4,4-di-n-hexyl-biphenyl. The measurements yield the following parameter values: d = 23.92 A?, q0 = 0.268 A??1 and the critical exponents γ = 1.51 ± 0.12, ν = 0.65 ± 0.06, ν = 0.70 ± 0.08. At the temperature t = 10?3 (t = TTc?1) the correlation lengths are ξ = 390 A? and ξ = 1080 A?.  相似文献   

2.
The interaction of three drift waves is considered at finite parallel wavelength. The coupling to ion sound waves has a profound effect on the saturation levels. For k|Ln~ 1. turbulent amplitudes are of the magnitude eΦ?Te1kLn as predicted by usual estimates, in contrast to previous studies neglecting this effect.  相似文献   

3.
The dependence of inclusive cross sections of the production of hadrons pp → hX on p (and also on x and √s) is calculated at high energy in the region of small p ? 1–2 GeV. The model of production and decay of quark-gluon strings is used under the simplest assumptions about the k dependence of the quark distributions in nucleons ~ exp(?γ1k2) and about the form of the string fragmentation function G?hexp[?γh(p ? zk)2] where γ1 and γh are some constants. The theory reproduces all existing experimental data and yields the “seagull effect” for the dependence of 〈p〉 on x. Predictions are given for the p dependence of the spectra of π± mesons produced at high energies at SPS and other future colliders.  相似文献   

4.
Atom transport in high-purity tin single crystals due to the influence of large direct currents has been measured by the “vacancy flux” technique. Cylindrical specimens were selected with c-axis oriented with 9° perpendicular or parallel to the direction of current flow. Rates of both longitudinal and transverse dimensional changes were used to calculate the anode-directed atom drift velocity. The results gave Z16?6 = ?18±2 and z1? = ?18 ±2, where Z1 is the effective charge number and ?6 = 0.89 and ? = 0.54 are the estimated correlation factors in the parallel and perpendicular directions. These values for Z1 are appreciably smaller than the results reported earlier for polycrystalline tin by Kuz'memko. The activation energies for Z1? agree within experimental error with those of self-diffusion.  相似文献   

5.
Magnetic and optical properties of two types of F centres, calledF(F?) and F (Cl?), created in BaClF and SrClF tetragonal crystals are described. The experimerttal position of the absorption bands and the [g] principal values of each centre are the following at 78K. In BaClF, F(Cl?): λ=438nm, λ=550nm, g=1.9690 ± 0.0003, g=1.9798±0.0003; F(F?): λ=532nm, λ=430nm446nm, g=1.9836 ± 0.0003, g=1.9695±0.0003. In SrCIF, F(Cl?): γ=380nm, λhu=465nm, g=1.996±0.002, g=1.993±0.002; F(F?): λ=410nm, λ=345nm363nm, g=1.997±0.001, g=1.993+0.001. (∥ and refer to the light polarization or the magnetic field direction with respect to the fourfold axis of the crystal).This attribution disagrees with that proposed by Nicklaus and Fischer, but accounts for the values of the energy levels of F(F?) and F(C1?) in BaClF and SrClF calculated by S. Lefrant and A.H. Harker.  相似文献   

6.
At about 200K where the Hall coefficient of p-Te reverses its sign, magnetophonon oscillation of electron in the conduction band was observed for the first time in H6c and Hc. It was attained by measuring the second derivative of the longitudinal magneto-Seebeck coefficient (?2α6/?H2). It is found to be explained fairly well by a simple parabolic band model even for H6c. Effective mass values of the conduction band at 200K are deduced on an interpretation; m1=0.160m0 and m16= 0.072m0. Rather large contribution of electron in ?2α6/?H2 may be due to the enhanced electron diffusion in a transition region from p-type to intrinsic as reported recently in p-InSb. This interpretation is supported also by the oscillation of longitudinal magnetoresistance (?2?6/?H2) which was observed for H6c.  相似文献   

7.
The Heidelberg shape-effect model for heavy-ion tensor interactions is reformulated and generalized using the Hooton-Johnson formulation. The generalized semiclassical model (the turning-point model) predicts that the components of the tensor analysing power T2q have certain relations with each other for each type of tensor interaction (TR, TP and TL types). The predicted relations between the T2q are very simple and have a direct connection with the properties of the tensor interaction at the turning point. The model predictions are satisfied in quantum-mechanical calculations for 7Li and 23Na elastic scattering from 58Ni in the Fresnel-diffraction energy region. As a consequence of this model, it becomes possible to single out effects from a TP? or TL-type tensor interaction in polarized heavy-ion scattering. The presence of a TP-type tensor interaction is suggested by measured T20/T22 ratios for 7Li+58Ni scattering. In the turning-point model the three types of tensor operator are not independent, and this is found to be true also in a quantum-mechanical calculation. The model also predicts relations between the components of higher-rank tensor analysing power in the presence of a higher-rank tensor interaction. The rank-3 tensor case is discussed in detail.  相似文献   

8.
The generalised Gruneisen parameters γ′ = ?? log ω/??′ and γ″ = ?? log ω/??″ have been calculated for various normal mode frequencies using the force model for Zirconium obtained on Keating's approach. There is a general agreement between the normalised frequency distribution curve of Zirconium obtained on the present model and that of Bezdek et al. The temperature dependence of the effective Gruneisen functions γ?(T) and γ?| (T) has been calculated using the procedure of Blackman. The high temperature limits of γ?(T), γ?|(T) and γ?v are in good agreement with those obtained by Goldak et al. from an analysis of the thermal expansion data of Zirconium.  相似文献   

9.
The behaviour of the transport coefficients of a Van der Waals fluid is studied in the one-phase region along the critical isochore of the liquid-vapour phase transition. When ?=(T?Tc)Tc→0 the strongest singularity is found in the case of the bulk viscosity (???2). The divergence of the heat conductivity is shown to be weaker than ??13. The shear viscosity tends to a finite limit. The coefficients of the asymptotic laws are explicitly given. All the results are established in the region where the Ornstein-Zernike theory applies.  相似文献   

10.
We have derived an expression for the adiabatic differential temperature change (?T?H)s of a semiconductor in the extreme quantum region. The transition to non-degeneracy is characterised by a sharp negative dip in (?T?H)s, which may be greatly modified by the Zeeman splitting. A numerical calculation of (?T?H)s has been made for GaAs with electron concentrations of 1.2 × 1016 and 3.8 × 1016 cm?3 at temperatures of 2,1 and 0.5 K.  相似文献   

11.
The Callan-Gross relation is shown to be consistent with MIT-SLAC data for σL(Q2)σT(Q2) for x ? 0.33 in deep inelastic eN scattering, despite the fact that these data are taken in the large Q2 region where F1 and F2 individually exhibit scaling violation. Comparison is made with asymptotic freedom predictions, and color excitation is proposed to explain large values of σLσT at small x.  相似文献   

12.
The cross sections for π±, K±, p, and p production in pp collisions have been measured at transverse momenta from 0.48 up to 2.21 GeV/c at 70 GeV. The data are compared with results obtained at lower and higher proton energies and also with the quantum chromodynamics parton model (QPM) calculations. Common behaviour of the cross sections of the form g(p)?(x) in the energy range above 200 GeV does not take place at lower energies. Qualitatively QPM fits the data and the best agreement is for π+/π? and K+/π+ ratios.  相似文献   

13.
We consider the contribution to σLσt in deep inelastic lepton-hadron scattering from a certain class of 4-quark operators in the framework of QCD. We find for this case by explicit calculation that σLσT is of order g2(Q2), with g2(Q2) the running coupling strength of QCD, in agreement with a general result of Politzer.  相似文献   

14.
Spin lattice relaxation T1 of naturally abundant 13C nuclei in squaric acid was measured close to the antiferroelectric-paraelectric phase transition temperature Tc = 373 K. A rapid increase in 1T1 is observed close to Tc coming from above, which follows the power law 1T1 ~ ε?1.4 where ε = (T ? Tc)Tc. This behaviour is explained on the basis of the two-dimensional character of the fluctuations.  相似文献   

15.
Reflectance spectra due to 3d core-levels of Ge have been measured in the photon-energy region from 29 to 38 eV by means of synchrotron radiation. Second-energy-derivative spectra have newly shown pairs of doublet structures with energy separation of the Ge 3d52?32 core-level splitting. The observed doublet structures are assigned to the transitions from the 3d52 and 3d32 core-levels to the flat regions of the conduction band around the particular symmetry points of Δ6c and L(3c(L6c, L4,5c).  相似文献   

16.
The specific heat CP is found to vary as dRdT in the critical region above TN for the antiferromagnets GdSb and HoSb. This correspondence holds despite a dramatic difference between the two systems in the strength of the divergence CP = A??α, ? = (T ? TN)TN, where for HoSb we find α = 0.83 ± 0.10 while for GdSb α = 0.20 ± 0.10.  相似文献   

17.
Oscillator strengths for 11S?n1P transitions for some members of the helium isoelectronic sequence have been calculated by utilizing the dipole length, velocity and acceleration forms of the transition matrix element with coupled H.F. wave functions. Good agreement has been obtained between the values of the oscillator strengths. The quantities (?A??L) and (?A??V) decrease slowly with nuclear charge Z, whereas (?L-?V) first increase to a maximum value and then decreases slowly.  相似文献   

18.
EPR of 61Ni+ doped CuGaS2 at 4.2 K leads to the following experimental data: g = 1.918 ± 0.006 A  < 12 × 10-4cm-1, g = 2.328±0.006 A = (65±2) × 10-4cm-1. High axial field splitting of 2T2 state stabilizes the center against Jahn-Teller interaction. Covalency reduction factor k is 0.76.  相似文献   

19.
The simplest four-quark SU(2) ? U(1) models with an anomally-free heavy lepton sector can have two charged heavy leptons and one or two neutral leprons. Such models also explain the rise in R (the ratio of hadronic to muon pair production in e+e? collisions). We study some consequences of different choices of leptonic numbers for L1 and L2. In particular, we derive, the leptonic decay width when several final-stae leptons are massive; the cross section for e+e?L1L2 production; the branching ratio for e+e?L2L2e3μ+missing energy.  相似文献   

20.
Let 0 ?q(x) ∈L1,loc(Rm),m? 1.Consider the operatorT0 = ?Δ+q with domain consisting of all bounded measurable functions u(x), x ∈ Rm, having bounded support, for which the distribution ?Δu+qu belongs to L2(Rm). The main result of the paper is essential self-adjointness of T0 in L2(Rm). The proof is independent of a method due to Kato who recently established the self-adjointness of a maximal Schrödinger operator corresponding to such potential.  相似文献   

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