共查询到20条相似文献,搜索用时 46 毫秒
1.
We study the electromagnetic radiation at twice the plasma frequency, which emerges because of the interaction of two identical counterpropagating short laser pulses in a rarefied plasma and caused by excitation of small-scale standing plasma waves in the pulse overlap region. The energy, spectral, and angular characteristics of radiation are investigated, and the dependence of these characteristics on the parameters of the laser pulses is analyzed. The possibility of applying this effect for diagnostics of localized plasma oscillations is discussed. 相似文献
2.
The theory of the electromagnetic radiation from channeled particles is developed with inclusion of a virtual photon interaction with the crystal. Simple estimates are made for the spectral and angular distribution of the radiation. It is shown that the polarisation of the medium may lead to a drastic shrinking of the frequency range allowed for the radiation. The possibility of an increase of the transverse energy of a particle caused by radiation is predicted. 相似文献
3.
R. Tomaschitz 《Applied physics. B, Lasers and optics》2010,101(1-2):143-165
Superluminal radiation from electrons accelerated in electromagnetic waves is investigated. The radiation field is a Proca field with negative mass-square, minimally coupled to the electron current. The spectrum is continuous in the ultra-relativistic regime, where steepest-descent asymptotics can be used to evaluate the power coefficients. The time averaging of Lissajous orbits in polarized wave fields is discussed, and the tachyonic spectral densities of electrons orbiting in intense laser beams are derived. In the ultra-relativistic limit, realized by high injection energy or high field intensity, the spectral functions are evaluated in closed form in terms of Airy integrals. In contrast to electromagnetic radiation, there is a longitudinal polarization component, and oscillations emerge at high beam intensity in the longitudinal and transversal spectral slopes, generated by the negative mass-square of the tachyonic quanta. The thermal ultra-relativistic electron plasma of two active galactic nuclei is analyzed in this regard, based on TeV spectral maps obtained with imaging air Cherenkov detectors. Specifically, tachyonic cascade fits are performed to γ-ray flares of the TeV blazars RGB J0152+017 and 3C 66A, and the transversal and longitudinal radiation components are disentangled in the spectral maps. The curvature of the spectral slopes is shown to be intrinsic, caused by the Boltzmann factor of the electronic source plasma radiating the tachyonic cascades. 相似文献
4.
The paper considers the action of an external radiation field with arbitrary spectral composition on an electron moving in the field of a monochromatic plane electromagnetic wave (the first wave). The problem is studied of the change in the average energy of a relativistic electron as a result of its interaction with the radiation field. Conditions are found under which the acceleration of the electron by the external field is compensated by the energy loss due to natural radiation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 7–16, January, 1973. 相似文献
5.
6.
N. N. Rozanov 《Optics and Spectroscopy》2002,92(2):239-242
Propagation of short pulses of electromagnetic radiation in a transparent medium with a frequency dispersion is considered for the linear and nonlinear modes. The role of back reflection of radiation in the spectral regions with the negative dielectric constant was clarified. For the nonlinear mode, the exact form of the stationary solitary wave whose profile includes a point with infinite steepness is found. 相似文献
7.
A. G. Zagorodnii A. S. Usenko I. P. Yakimenko 《Radiophysics and Quantum Electronics》1994,37(10):798-814
The electromagnetic radiation field of sources arbitrarily distributed throughout space is found for the case of a semi-bounded plasma when the charged plasma particles are specularly and randomly scattered by the plasma interface. The spectral distributions of the thermal radiation emitted by a nonisothermal semi-bounded plasma into an external medium having a nonzero temperature are calculated.Institute of Theoretical Physics, Ukrainian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, No. 10, pp. 1237–1261, October, 1994. 相似文献
8.
Sten Yngström 《International Journal of Theoretical Physics》1994,33(7):1479-1501
The theoretical derivation of a new spectral line intensity formula for atomic radiative emission is presented. The theory is based on first principles of quantum physics, electrodynamics, and statistical physics. Quantum rules lead to revision of the conventional principle of local thermal equilibrium of matter and radiation. Study of electrodynamics suggests absence of spectral emission from fractions of the numbers of atoms and ions in a plasma due to radiative inhibition caused by electromagnetic force fields. Statistical probability methods are extended by the statement: A macroscopic physical system develops in the most probable of all conceivable ways consistent with the constraining conditions for the system. The crucial role of statistical physics in transforming quantum logic into common sense logic is stressed. The theory is strongly supported by experimental evidence. 相似文献
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10.
Light scattering property of environment is very important in theoretical study and application of the remote sensing. What's more, it is valuable for infrared radiation, imaging, and the detection of target and tracking. In this paper, solar and atmospheric background radiation, and their scattering property from target are discussed. BRDF (Biodirectional Reflectance Distribution Function) is a very important quantity that shows the radiation and reflection feature of target. According to electromagnetic radiant and scattering theories, the relationship between laser radar scattering cross section (LRCS) and BRDF is introduced. LOWTRAN model is an effective method of calculating the spectral distribution of solar and atmospheric radiation. Here it is applied to compute solar and atmospheric background radiation scattered from a target. The relative equations are deduced. Thus, the spatial and spectral distribution of scattering light is given. As a special example, for the Lambert's surface, the equations are simplified. As a result, the spatial and spectral distributions scattering radiation of solar and atmospheric background from a rough painted surface are present. The scattering of solar radiation plays a primary role in MIR region, but scattering of atmospheric background radiation is higher in LIR region. At the same time, there is obviously specular reflectance for solar radiation due to coherent scattering from rough surface. 相似文献
11.
S. V. Barakhvostov M. B. Bochkarev N. B. Volkov K. A. Nagayev V. P. Tarakanov S. I. Tkachenko O. R. Timoshenkova E. A. Chingina 《JETP Letters》2011,94(7):549-555
The results of the experiments on the destruction of micron-diameter conductors by an electromagnetic pulse, which is generated
in an inhomogeneous coaxial line by a high-voltage power source and has a subnanosecond front, are reported. The role of electrodynamic
processes in the surface layer of microconductors and in environment in the formation of the spatial structure of the plasma
channel and in the transformation of the energy of the source to the energy of radiation has been revealed. The spectral characteristics
of the radiation of the plasma channel have been analyzed. It has been shown that the radiation spectrum at the time of the
formation of the plasma corona is continuous. The most intense spectral lines of copper (510.554, 515.324, 521.82 nm) appear
at ∼3 ns after the formation of the plasma corona. The temperature has been estimated from the ratio of the intensities of
the spectral lines as T
e
∼ 0.7 eV. 相似文献
12.
开展了波长为532 nm、脉宽为8 ns的纳秒激光诱导空气等离子体射频电磁辐射特性实验研究,基于锥形天线探测空气等离子体在30-800 MHz频谱范围有较强的射频电磁辐射,是等离子体内电偶极子振荡变速运动造成的.实验结果表明:随激光能量增加,30-200 MHz范围内射频辐射强度逐渐变强,但360-600 MHz频率范围射频辐射强度逐渐变弱.等离子体射频辐射的空间分布依赖于入射激光的偏振方向,当激光偏振方向与天线放置方向一致时,该方向上空气等离子体的射频辐射强度高,谱线较丰富.射频辐射总功率随激光能量先增加后降低,采用等离子体电子密度变化对等离子体频率及等离子体衰减系数影响(制约)关系,对射频辐射总功率随激光能量的变化规律进行了解释. 相似文献
13.
S. V. Dyul'Dya N. N. Nasonov V. V. Rozhkov V. I. Vit'Ko A. V. Vojtsenya 《辐射效应与固体损伤》2013,168(3-4):293-305
The spectral, angular and polarization characteristics of the electromagnetic radiation generated by relativistic positrons reflected at small angles by a solid surface are obtained in the dipole approximation of classical electrodynamics. The effects investigated are produced by coherent interaction of the reflected positrons with atomic chains on the solid surface. The interference effects accompanying positron multireflection by two parallel solid surfaces are discussed. 相似文献
14.
The spectral distribution of the intensity of radiation from a chain of 1 N > equidistant relativistic charged particles uniformly rotating about a dielectric ball weakly absorbing radiation, in its
equatorial plane is investigated. In the case of a single particle (N = 1) and of a special values of problem parameters (frequency of charge gyration, distance between the charge and the ball
surface, dielectric permittivity of the ball material), the radiation at certain harmonics with k ≫ 1 may be more intensive by tens of times than that for a charge uniformly rotating in a continuous and infinite medium
(having the same dielectric permittivity as that for the ball material). Numerical results testify that if one replaces a
single particle rotating about a ball by a chain of N = mk charges (m = 1;2;3...), then the radiation may be amplified by N
2 times due to the constructive interference of electromagnetic waves generated by different charges of the chain. The increase
in radiated energy is caused by an additional work of external forces sustaining the uniform rotation of charged particles
about a dielectric ball. 相似文献
15.
I. M. Sokolov D. V. Kupriyanov M. D. Havey 《Journal of Experimental and Theoretical Physics》2011,112(2):246-260
Based on the developed quantum microscopic theory, the interaction of weak electromagnetic radiation with dense ultracold
atomic clouds is described in detail. The differential and total cooperative scattering cross sections are calculated for
monochromatic radiation as particular examples of application of the general theory. The angular, spectral, and polarization
properties of scattered light are determined. The dependence of these quantities on the sample size and concentration of atoms
is studied and the influence of collective effects is analyzed. 相似文献
16.
V. M. Babin V. V. Vorob’ev A. S. Medvedev E. S. Mironchuk A. A. Narits A. D. Kondorskii 《Bulletin of the Lebedev Physics Institute》2013,40(5):122-125
Numerical calculations are performed and spectral characteristics and spatial field distributions are studied upon excitation of a chain of two and three nanoparticles by a near-field optical microscope probe. It was found that there is a set of frequencies near the absorption line of nanoparticle material, at which the electromagnetic field can most efficiently propagate along the chain. It is shown that the efficiency of the electromagnetic energy transfer due to the quadrupole interaction between particles can exceed the efficiency of the transfer caused by the dipole interaction. 相似文献
17.
We have found an analytical expression for the absorption coefficient of electromagnetic radiation in a quantum channel with a parabolic confinement potential. The calculation has been performed using the second-order perturbation theory taking into account the scattering of a quasi-one-dimensional electron gas by ionized impurities. We have analyzed the dependences of the absorption coefficient on the frequency of the electromagnetic radiation and the magnetic field. The appearance of additional resonant peaks, which are caused by scattering by impurities, has been found. 相似文献
18.
Yu. B. Kotov V. D. Popov T. A. Semenova V. F. Fedorov 《Russian Journal of Physical Chemistry B, Focus on Physics》2012,6(1):109-111
The special features of the generation of microwave radiation by a high-power air explosion accompanied by ionizing radiation
are discussed. Coherent pulse caused by asymmetry of the ejection of gamma quanta from a source, incoherent bremsstrahlung
of a partially ionized plasma, incoherent radiation of the shock wave front, and radiation in spectral lines lying inside
air transparency windows are considered. 相似文献
19.
The late time asymptotics of the physical solutions to the Lorentz–Dirac equation in the electromagnetic external fields of simple configurations–the constant homogeneous field, the linearly polarized plane wave (in particular, the constant uniform crossed field), and the circularly polarized plane wave–are found. The solutions to the Landau–Lifshitz equation for the external electromagnetic fields admitting a two-parametric symmetry group, which include as a particular case the above mentioned field configurations, are obtained. Some general properties of the total radiation power of a charged particle are established. In particular, for a circularly polarized wave and constant uniform crossed fields, the total radiation power in the asymptotic regime is independent of the charge and the external field strength, when expressed in terms of the proper-time, and equals a half the rest energy of a charged particle divided by its proper-time. The spectral densities of the radiation power formed on the late time asymptotics are derived for a charged particle moving in the external electromagnetic fields of the simple configurations pointed above. This provides a simple method to verify experimentally that the charged particle has reached the asymptotic regime. 相似文献
20.
Yu.?P.?Vo?nov N.?F.?Gabitova V.?S.?Gorelik L.?I.?Zlobina P.?P.?Sverbil’ 《Physics of the Solid State》2009,51(7):1409-1413
This paper reports on a comparison of transmission, reflection, and secondary radiation spectra of unloaded synthetic opals and samples filled with the sodium nitrite ferroelectric (NaNO2). The radiation is provided by semiconductor light-emitting diodes operating in the ultraviolet and visible spectral regions. Selective excitation of slow electromagnetic waves in a photonic crystal, an effect observed when the exciting radiation frequency approaches the stop-band edge, is studied. 相似文献