共查询到20条相似文献,搜索用时 31 毫秒
1.
W. Stocker 《Zeitschrift für Physik A Hadrons and Nuclei》1966,193(2):310-317
In order to obtain a regular but energy-dependent nuclear potential, the following modification of the separation method ofMoszkowski andScott is used: we replace the nuclear potentialv c (r) by a long-range potentialv l (r)=v c (r) Θ(r? d 0) together with a short-range energy dependent repulsionv s =h(k) Θ(r c ?r), whered 0 is the separation distance for vanishing energy andr c is the hard-core radius. The potentialv=v s +v l (r) is fitted to theS-wave scattering data and the binding energy of the deuteron.h(k) turns out to be almost proportional to the scattering energyE rel for energiesE rel<150 MeV. 相似文献
2.
Expressions for the probabilities of l-photon transitions (for arbitrary l) between the upper valence band v and lower conduction band c at two-photon resonance on the adjacent transition between the band c and the upper conduction band c 1 are obtained by means of the S transformation of the electron-photon Hamiltonian. The effects of electron band spectrum transformation and photon reemission are taken into account. 相似文献
3.
A consistent procedure for determining the ionization potential of a large metal cluster of radius R N, v , consisting of N atoms and N v vacancies, is proposed. The perturbation theory in small parameters R v /R N, v and L v /R v (Rv and L v are average distance between vacancies and the length of electron scattering on vacancies, respectively) is constructed in the effective-medium approximation for the electron ground state energy. The effective vacancy potential profile, the electron scattering phase and length are calculated by the Kohn–Sham method for a macroscopic metal in the stable jelly model. The obtained analytical dependences can be useful to analyze the results of photoionization experiments and to determine the size dependence of the vacancy concentration, including that near the melting temperature. 相似文献
4.
A. A. Bykov 《JETP Letters》2009,89(11):575-578
The effect of millimeter microwave radiation on the electron transport of two-dimensional (2D) ballistic microbars formed on the basis of individual GaAs quantum wells at a temperature of T = 4.2 K in magnetic fields B < 0.6 T has been investigated. Differences have been revealed in the magnetic field dependences of the microwave photoresistance of a 2D electron gas in Hall bars with a length L and a width W for the cases L, W > l p and L, W < l p , where l p is the electron mean free path for momentum. The microwave photoresistance in macroscopic bars (L, W > l p ) is a periodic alternating function of the inverse magnetic field; in microbars (L, W < l p ), it is a periodic positive function of 1/B. The experimental results indicate that the mechanisms of the microwave photoresistance of a 2D electron gas are different for macroscopic and microscopic bars. 相似文献
5.
I. B. Krasnyuk 《Technical Physics》2007,52(5):565-570
The penetration of a magnetic flux into a type-II high-T c superconductor occupying the half-space x > 0 is considered. At the superconductor surface, the magnetic field amplitude increases in accordance with the law b(0, t) = b 0(1 + t)m (in dimensionless coordinates), where m > 0. The velocity of penetration of vortices is determined in the regime of thermally activated magnetic flux flow: v = v 0exp?ub;?(U 0/T )(1-b?b/?x)?ub;, where U 0 is the effective pinning energy and T is the thermal energy of excited vortex filaments (or their bundles). magnetic flux “Giant” creep (for which U 0/T? 1) is considered. The model Navier-Stokes equation is derived with nonlinear “viscosity” v ∝ U 0/T and convection velocity v f ∝ (1 ? U 0/T). It is shown that motion of vortices is of the diffusion type for j → 0 (j is the current density). For finite current densities 0 < j < j c, magnetic flux convection takes place, leading to an increase in the amplitude and depth of penetration of the magnetic field into the superconductor. It is shown that the solution to the model equation is finite at each instant (i.e., the magnetic flux penetrates to a finite depth). The penetration depth x eff A (t) ∝ (1 + t)(1 + m/2)/2 of the magnetic field in the superconductor and the velocity of the wavefront, which increases linearly in exponent m, exponentially in temperature T, and decreases upon an increase in the effective pinning barrier, are determined. A distinguishing feature of the solutions is their self-similarity; i.e., dissipative magnetic structures emerging in the case of giant creep are invariant to transformations b(x, t) = βm b(t/β, x/β(1 + m/2)/2), where β > 0. 相似文献
6.
A classification of the eigenstates of the harmonic quadrupole oscillator is given within the framework of the Lie-AlgebraB 2 ofR(5). There still exists the problem of complete classification, since the multiplicityd v (l 2) for seniority numbersv≧6 may be greater than one. For these multiplicitiesd v (l 2) easily managable recursion formulae are derived and therefore their explicit calculation for arbitraryv andl 2 is easily possible. 相似文献
7.
The electron excitation of nucleon resonances is discussed both from the theoretical and from the experimental point of view. This discussion is based on a phenomenological approach that employs the conservation of the electromagnetic and vector-meson hadronic currents and the requirements of limiting chiral invariance. For the electron excitation of Jπ=1/2±,3/2±,5/2±,... nucleon resonances, the structure functions are defined in terms of Sachs transition form factors. The resulting resonance structure functions for l+N → l+R processes are used in parametrizing smooth (background) structure functions for l+N → l+X inelastic scattering. 相似文献
8.
A set of observables describing a macroscopic system — an observation level — defines a generalized canonical statistical operator ?. The case is considered that parts þ v of the Hamiltonian form the observation level; it leads to systems with several temperatures. Generally the Hamiltonians þ v do not only operate in partsU v of a product space, so that the statistical operator ? is not a product of operators ? v . In this case the observation level is called undivisible. Examples: a system with different Zeeman and interaction temperatures; several temperatures within a system of effective spins>1/2; a Fermi or Bose gas with different spin and orbital temperatures. Zeroth, first, second, third law of such generalized statistical thermodynamics are discussed. As a consequence of the undivisibility each internal energyU v depends on all temperaturesT 1,...,T v ,... Hence there are more heat capacities than in normal thermodynamics. However, there exists only one entropy for the whole system. Finally the possibility of linear transformations of the Hamiltonians þ v , is considered. 相似文献
9.
Darlan A. Moreira Gilberto Corso 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(5):120
The Lucena network (LN) is the dual of a multifractal partition of the square. We analyzethe relation between the typical topologic distance l and the number ofvertices Nof the LN. The multifractal partition has one parameter ρ which controls thegeometrical asymmetry of the multifractal. In the limit of ρ → 1 the blocks of thepartition are squared, the connections amont the blocks are short range, the LN is moreregular and the relation l ∝ √N is observed. For the limit ρ → 0 the blocks arestrongly asymmetric, long range connections appear, and the topologic distance followsl ∝(log?N)α, a weak smallworld phenomenon. For any network size we calculate analytically the size of the minimumdistance lmin (ρ → 0) and the maximaldistance lmax (ρ → 1). The distance in theweak small world regime is calculated using the number of vertices inside a radius oflength land taking into account the network average connectivity and the exponent α. 相似文献
10.
11.
A. V. Golubkov L. S. Parfen’eva I. A. Smirnov D. Wlosewicz H. Misiorek J. Mucha A. Jezowski A. I. Krivchikov G. A. Zvyagina I. B. Bilich 《Physics of the Solid State》2007,49(11):2042-2046
This paper reports on a measurement of the heat capacity at constant pressure (C p ) in the temperature range 3–320 K and the sound velocity (v) at 77 K for the “light” heavy-fermion compound YbMgCu4. The present experimental data on C p and v of YbMgCu4, combined with our earlier phonon thermal conductivity data for YbMgCu4 in the range 5–300 K, have been used to calculate the phonon mean free path l in this compound. The temperature dependence of l obtained is found to be characteristic of classical amorphous materials. 相似文献
12.
V. P. Dick 《Optics and Spectroscopy》2007,103(4):632-639
The maximum value of the light extinction coefficient μ, which can be observed in a dispersive medium with a relative refractive index n of the scattering particles, is studied within the framework of a quasi-crystalline approximation for nonabsorbing dispersive media consisting of monodisperse spherical scatterers. A change in the diffraction parameter x of the scattering particles and their volume concentration c v is accompanied by nonmonotonic variations of the extinction coefficient, and the function μ(x, c v ) exhibits several maxima. The dimensions and concentrations of particles are determined, for which the extinction coefficient reaches the absolute maximum μmax. The μmax value exhibits a monotonic growth with increasing relative refractive index n of the scattering particles. The conditions of validity of the Ioffe-Regel criterion of radiation localization have been studied. It is established that the localization in nonabsorbing dispersive media can be observed only for n ? 2.7. The intervals of x and c v in which the criterion of radiation localization is satisfied in dispersive media consisting of particles with n = 3.0 and 3.5 are determined. 相似文献
13.
The scattering amplitudes of point charged particles is calculated analytically taking into account the spin–orbit interaction. We have considered two cases typical of a hydrogen-like plasma: scattering of an electron by a heavy ion and scattering of an electron by a free electron. The results have been obtained taking into account the ranges of low collision energies smaller than α2 m e c 2, where α is the fine structure constant. 相似文献
14.
15.
The velocityv of the propagation of discharge along the anode of a self-quenchingG—M-counter is a function of total pressureP, pressure of the quenching gasP D, radius of the cathoder a and of the anoder i andV ü the difference between working- and starting-potential. For the mixtures argon-methylal, argon-alcohol and helium-alcohol isv=v 0·exp[k·(V ü/V e)1/2] withv 0 the velocity at the starting potentialV e v 0=(a+b·P D/P)·V n 1/2 ·exp [(c?d·PD/P·V n ?1/2 ] andV n=V e·(lnr a/r i)?1.k, a, b, c andd are characteristical constants of the filling gas. 相似文献
16.
G. Sommer 《Zeitschrift für Physik A Hadrons and Nuclei》1966,193(3):426-438
Unphysical regions on the right hand cut in partial wave dispersion relations for a two-particle processA+B→A′+B′ are expressed by measurable quantities, under the assumption that there is only one important 2-particle channel in the unphysical region. The solution is unique, if the phase shiftδ l for the elastic scattering in the channel responsible for the appearance of the unphysical region takes a value between 0 andπ at the physical threshold forA+B→A′+B′. The difference between non resonant (δl≠π/2 in the unphysical region) and resonant contributions is shortly discussed. 相似文献
17.
A. V. Gordeev 《Czechoslovak Journal of Physics》2006,56(2):B73-B79
The current equilibrium is investigated, where the generation of the Hall electric field on the magnetic Debye radius r B = B 0/(4πen e) is considered by the drifting of the relativistic electrons crosswise to the strong magnetic field. In this case, the electron propagation is possible at the distance d that is essentially larger than the electron radius of the backward reflection in the magnetic field r 0 ? m e v z c/(eB 0). The instability of the joint drift motion of ions and electrons is investigated for the frequency oscillation w much higher than the ion cyclotron frequency w Bi and by 4π n i m i c 2 ? B 0 2 and (k · B 0) = 0. It is shown that the resonance effects by the ion beam’s plasma frequency w ? kv 0 = w pi leads to the generation of the nonpotential perturbations with the characteristic increment Imw ~ 10?1 ÷ 10? 2 w pi. Estimates show that the instability, associated with the propagation of the high-energy ion beam through the strong magnetic field, can essentially be like the edge-localized mode in tokamaks. 相似文献
18.
The isotopically invariant Dunham parameters U mj , Δ mj H and Δ mj Cl were determined by simultaneously fitting the line centers of vibration-rotation transitions of six isotopic HCl forms in the ground electronic state. Fitting included relations between U mj values. The parameters of the isotopically invariant potential of HCl were determined using independent U m0 and U m1 values. The contributions to the vibrational terms of H35Cl caused by violation of the Born-Oppenheimer approximation were calculated. 相似文献
19.
We present an exact diagrammatic approach for the problem of dimer-dimer scattering in 3D for dimers being a resonance bound state of two fermions in a spin-singlet state, with corresponding scattering length a F . Applying this approach to the calculation of the dimmer-dimer scattering length a B , we recover exactly the already known result a B = 0.6 a F . We use the developed approach to obtain new results in 2D for fermions and bosons. Namely, we calculate bound state energies for three bbb and four bbbb resonantly interacting bosons in 2D. For the case of resonance interaction between fermions and bosons, we exactly calculate bound state energies of the following complexes: two bosons plus one fermion bbf, two bosons plus two fermions bf↑bf↓, and three bosons plus one fermion bbbf. 相似文献
20.
M. Finger 《Physics of Particles and Nuclei》2008,39(3):348-381
A survey of available experimental data on the measurement of spin observables in neutron-proton (np) elastic scattering in the neutron energy range 200–600 MeV is presented. Sixteen spin observables (the polarization of recoil particles P 0n00, the analyzing power A 00n0, the spin correlation parameters A 00nn , A 00ss , A 00sk , and A 00kk , the spin transfer parameters K 0nn0, K 0ss0, and K 0sk0, the depolarization parameters D 0n0n , D 0s0s , and D 0s0k , and the three-spin parameters N 0nkk , N 0skn , N 0ssn , and N 0sns for energies of 200–590 MeV and scattering angles in the center of mass system of 60°–164°) were studied in experiments using polarized neutron beams and polarized proton targets at the Paul Scherrer Institute. The results of these investigations present a complete set of precision data on np elastic scattering which, along with the complete set of data for proton-proton (pp) elastic scattering obtained earlier, provides a basis for unambiguous determination of the amplitudes of the scattering matrix for nucleon-nucleon (NN) elastic scattering for the channel with the isotopic spin I = 0 and makes it possible to describe NN interaction in a model-independent way. 相似文献