共查询到20条相似文献,搜索用时 31 毫秒
1.
Theory of second harmonic generation at a metal surface is developed, when surface plasmon-polaritons are resonantly excited by the incident electromagnetic field. For harmonic generation from small metallic spheres characterized by the dielectric function ?1(ω) + i?2(ω), the resonant enhancement of the second harmonic intensity is predicted to be of the order of (. The resonant enhancement is much smaller for the case of a metallic grating. 相似文献
2.
P. Halevi 《Surface science》1978,76(1):64-90
A review of polariton modes at interfaces composed of two semiinfinite, homogeneous, and isotropic media is given. Both media are characterized by frequency-dependent dielectric functions ?i(ω), i = 1, 2, and may become “interface-wave-active” in different frequency regions. The conditions for the existance of propagation windows are analyzed and applied to two particular cases: an interface composed of (a) two dielectrics with dielectric functions , where ?t8i are the dielectric constants for very large frequencies and ωTi and ωLi are the transverse and longitudinal phonon frequencies; (b) two conductors with dielectric functions , where ωiare the plasma frequencies. In the first case there exist two propagation windows in the infrared region, while in the second case there is one propagation window in the ultraviolet, visible, or infrared region. The dispersion relations of the modes and their decay distances into the two media are presented, and various damping effects are discussed. The review is concluded with theoretical results on the optical excitation and detection (ATR) of the interface modes. 相似文献
3.
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
4.
We consider the class of non-integrable, non-linear equations, in 1+1 dimensions. We seek rational solutions K(ω1,ω2), which we call bi-solitons, with exponential type variables ωi = exp(γix + ρit). In this paper, we restrict to q = 2 and 3, and investigate the general q case in the following paper. We find that these bi-solitons exist when the operator Lq (with ± ?) can be factorized as the product of smaller order differential operators. Besides the trivial factorized bi-solitons, we show that there exist non-trivial ones whenever K may be written as Σlmaxx ωl2Fl(Z = ω1 + ω2). In order to understand the origin of the factorization property, to any polynomial K = Σωl2Fl(Z) we associate a linear transformation such that LqK has only the power ωl2 of K2. For q = 2 and 3, we find that there exist particular polynomials of this type restraining Lq to be a product of smallr order operators. For the full non-linear equations we verify that all the bi-solitons can be obtained from these particular polynomials. 相似文献
5.
In order to get dipole-moment derivatives, that are free from rotational contributions, we used Crawford's method applied to a new type of reference molecule. The agreement with earlier calculated rotational correction terms is good, the applicability of the new reference molecule is wider. The rotational contributions to the -quantities are presented for a number of C2v- and C3v-type molecules. 相似文献
6.
The temperature dependence of the field emission flicker noise spectral density functions has been investigated for potassium adsorbed on tungsten (112) planes by a probe hole technique. By integration of the spectral density functions the noise power for different frequency intervals Δ? is obtained. From the exponential temperature dependence of noise power “activation energies” qΔ? are determined. Plots of these energies versus coverage show a similar “oscillating” behaviour as recently found for or which indicates phase transitions of the adsorbed potassium submonolayers. The noise activation energies are discussed in terms of existing models and a comparison is made between the experimental q values and surface diffusion energies Ed as determined by conventional methods. 相似文献
7.
Masayuki Ito 《Physica D: Nonlinear Phenomena》1984,14(1):1-28
This paper is concerned with the competitive-diffusive systems , with homogeneous Dirichlet boundary conditions. From a global bifurcation view point, the dependency of steady-states on the parameters ai, bi, ci and di (i = 1, 2) is investigated. In particular, bifurcation of coexist ence solutions amd their stabilities are our main interests. 相似文献
8.
Calculations of vibrational and rotational level spacings of homonuclear inert gas diatomic molecules by numerical integration of the radial Schrödinger equation are presented. The potentials which were used for the ground states of Ar2, Kr2, and Xe2 were obtained from accurate fits to the molecular beam scattering data. From the calculated and Bv's, the following spectroscopic constants (in cm?1) were fitted: for Ar2ωe = 31.92, ωexe = 3.31, ωeye = 0.11, Be = 0.060, αe = 0.004; for , , , , ; for , , , , . 相似文献
9.
A theoretical investigation is carried out on the zero field current steps of a short Josephson junction under both the d.c. voltage Vd.c. and a.c. voltage Va.c. cos ωt. The steps occur when the condition is fulfilled, where , ωn is the nth eigenfrequency in the eigenfrequency in the junction cavity, p and N are integers. 相似文献
10.
Three-step optical resonance is used to execute state-selected transitions from the ground state of ICl to two van der Waals states, and , both of which correlate with the second dissociation limit, , of ICl. Since the B(0+) state also belongs to this limit, three out of five states converging to I + Cl1 are now accounted for. Principal constants of these states are: b′(2): Te = 18275.84, ωe = 31.093, ωexe = 1.672, ωeye = 0.0070, Be = 0.034834, αe = .001587, and De = 164.09 cm?1; b(1): Te = 18273.30, ωe = 26.75, ωexe = 0.882, Be = 0.03579, q = 0.00084, and De = 166.63 cm?1. In both states the equilibrium distance is near 4.2 Å, slightly greater than the sum of van der Waals contact radii, . The large value of q in the b(1) state indicates that, in the basis set (a = I, b = Cl, j = ja + jb) the b(1) and b′(2) states belong to j = 1 and j = 2 “complexes,” respectively. 相似文献
11.
J. Kwiatkowski 《Reports on Mathematical Physics》1973,4(3):203-210
The purpose of this paper is to prove the following theorem.Theorem. Given a countable subset Λ on the circle K and an integer-valued function n(λ) on Λ, there exists a dynamical system with discrete spectrum (X,,μ,T) such that Λ is the set of all eigenvalues of T and n(λ) is the multiplicity function of T if and only if there exist two systems of subgroups {Gi}i∈N and of the circle such that Λ = G ∪ S and where . 相似文献
12.
In this note we prove the following theorem. If in a flat space-time with metric gij(x) treferred to general coordinates xi a vector ξi(x) satisfies (Tijξj);i=0 (semicolon denotes covariant differentiation) for all energy-momentum tensors of the set ; Tij = Tji; Tijuiuj > 0 (where ui is a time-like vector)}, then the vector ξi defines a conformal motion. This theorem, which may be considered as a converse (in flat space-time) to a well-known result of Trautman, is a generalization of a result obtained by J. T. ?opuszański and J. Szczucka-Soko?owska [Reports on Mathematical Physics 11 (1977), 153] in which they assumed the vector ξi was a polynomial in Minkowski coordinates. 相似文献
13.
M. Fähnle 《Journal of magnetism and magnetic materials》1978,8(4):330-332
Within the framework of a perturbation theory and a quasicrystalline approximation we have solved the linearized equation of motion for the circular spin component S+j = Sxj + iSyj in a one-dimensional amorphous ferromagnet with periodic external excitation of the spin S+0 at site j = 0. It is shown that localized spin modes of the simple form with fall-off-length κ-1 are solutions of the ensemble-averaged equation of motion. On the other hand, we have a damping of extended spin waves according to exp(-Γt). A simple relation is derived between the fall-off-length κ-1 of localized spin modes and the damping factor Γ of extended spin waves. Analogous results hold for phonons in amorphous materials. 相似文献
14.
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
15.
The wavenumbers of the rotation-vibration lines of 14N16O are reported for the (2-0) and (3-0) bands. The full set of spectroscopic constants for the three bands (1-0), (2-0), and (3-0) has been determined with the method developed by Albritton, Schmeltekopf, and Zare for merging the results of separate least-squares fits. The vibrational constants ωe, ωexe, ωeye, and the vibrational dependence of the rotational constants have been deduced. The apparent spin-orbit constant and its centrifugal correction (including the spin-rotation constant) have a vibrational dependence of the following form: and ; the values of the constants in these two equations have been determined. 相似文献
16.
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
17.
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
18.
H. Kleinert 《Physics letters. [Part B]》1976,62(1):77-80
In quark gluon theory with very small bare masses, -ψ, spontaneous breakdown of chiral symmetry generates sizable masses Mu, Md, Ms, … We find (. Scalar densities have well determined non-zero vaccum expectations at an SU(3) breaking of the vacuum c′ ≡ 〈0|u8|〉/〈0|uo|0〉 ≈ ? 16% 相似文献
19.
Near the onset of intermittent chaos from quasiperiodic motion lying on an attracting 2D torus with rotation number ρ=ω2/ω1=(√5?1)/2, the power spectrum of the cartesian coordinate of the intersection point on the Poincaré section is studied. The Poincaré section is distorted from the ellipse near the onset of chaos. Then a sequence of spectral lines are excited at frequencies . Their intensities are found to obey the power law according as the Poincaré section has a sharp wrinkle or not. A similar spectrum is obtained also in the chaotic regime ε > 0. The mean value of time intervals of quasiperiodic states between two consecutive bursts and the square root of their variance are found to be inversely proportional to ε near the onset point g3 = 0. 相似文献
20.
Evans M. Harrell 《Annals of Physics》1977,105(2):379-406
This is a perturbative analysis of the eigenvalues and eigenfunctions of Schrödinger operators of the form ?Δ + A + λV, defined on the Hilbert space L2(Rn), where , A is a potential function and V is a positive perturbative potential function which diverges at some finite point, conventionally the origin. λ is a small real or complex parameter. The emphasis is on one-dimensional or separable problems, and in particular the typical example is the “spiked harmonic oscillator” Hamiltonian, , where α is a positive constant. When this kind of perturbation is very singular, the first-order Rayleigh-Schrödinger perturbative correction, (u0, Vu0), where u0 is the unperturbed eigenfunction, diverges. This analysis constructs explicitly calculable terms in a modified perturbation series to a finite order, by using linear operator theory in concert with approximation methods for differential equations. Along the way a connection between a W-K-B type approximation and Bessel functions is exploited. 相似文献