共查询到20条相似文献,搜索用时 156 毫秒
1.
A. V. Korol’ A. G. Lyalin O. I. Obolenskii A. V. Solov’ev 《Journal of Experimental and Theoretical Physics》1998,87(2):251-259
This paper develops an effective method for calculating the bremsstrahlung cross section with allowance for the polarization
mechanism. We calculate the cross section of bremsstrahlung produced in the scattering of electrons and positrons by H and
Kr atoms. We also demonstrate the important role of polarization bremsstrahlung in the formation of the total emission spectrum
over the entire frequency range.
Zh. éksp. Teor. Fiz. 114, 458–473 (August 1998) 相似文献
2.
This paper discusses the distinctive features of radiation of electromagnetic waves with anomalously large values of the wave
vector and small phase velocity that exist near narrow absorption lines. The distribution of radiated energy with respect
to angle and frequency is calculated for Čerenkov radiation and bremsstrahlung of the slow waves. It is shown that the angular
distribution of the slow-wave bremsstrahlung exhibits a characteristic maximum in the direction perpendicular to the plane
of motion of the particles.
Zh. éksp. Teor. Fiz. 112, 1557–1562 (November 1997) 相似文献
3.
4.
The radiation emission spectra of polarized photons emitted from charged particles in single oriented crystals are obtained
in Bayer-Katkov-Strakhovenko semiclassical approach. The results of numerical calculations are presented in the region of
small angles of incidence for which the coherent theory fails but the magnetic bremsstrahlung region is not yet achieved.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 3, 171–175 (10 February 1999) 相似文献
5.
K. Yu. Amosov V. A. Verzilov I. E. Vnukov B. N. Kalinin G. A. Naumenko A. P. Potylitsyn 《JETP Letters》1996,63(3):153-158
The radiation spectra from 900 and 400 MeV electrons in thin Ta, Cu, and Sn foils are measured at an angle of 19° with respect
to the direction of motion of the beam. The radiation yield and its dependence on the electron energy agree satisfactorily
with the theory of polarization bremsstrahlung. This result represents the first direct observation of polarization bremsstrahlung
from ultrarelativistic electrons in homogeneous condensed matter.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 3, 145–149 (10 February 1996) 相似文献
6.
V. P. Silin 《JETP Letters》1999,69(7):521-525
The laws characterizing the radiation of high harmonics due to the coherent bremsstrahlung effect are indicated in the limit
of high intensity of the laser pump photoionizing a gas in regime of suppression of the ionization barrier. It is shown that
the intensity of the harmonics is determined by the quantum properties of the electron distribution in an atom before it is
ionized.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 7, 486–490 (10 April 1999) 相似文献
7.
Electron-positron production processes occurring in the interaction of 1018–1020 W/cm2 laser radiation with high-Z targets are examined. Computational results are presented for the pair production and the positron yield from the target
with allowance for the contribution of pair production processes due to electrons and bremsstrahlung photons. Monte Carlo
simulations using the PRIZMA code confirm the estimates obtained. The possible positron yield from high-Z targets irradiated with 102–103 TW laser radiation is estimated to be 109–1011.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 4, 239–244 (25 February 1998) 相似文献
8.
A. Yu. Romanov V. P. Silin S. A. Uryupin 《Journal of Experimental and Theoretical Physics》1997,84(4):687-693
We investigate the Weibel instability in a plasma with a nonstationary three-temperature electron distribution generated by
inverse bremsstrahlung of an intense elliptically polarized electromagnetic wave. We show that electron-ion collisions in
this strong high frequency field are simultaneously the cause of the development of the instability and the reason it is suppressed.
We find plasma and radiation parameters for which spontaneous quasistationary solenoidal electromagnetic fields can increase
by many times.
Zh. éksp. Teor. Fiz. 111, 1245–1257 (April 1997) 相似文献
9.
We develop a quantitative theory of the effect of multiple scattering on the bremsstrahlung of ultrarelativistic electrons
in a thin layer of matter. The effect is an analog of the Landau-Pomeranchuk-Migdal (LPM) effect of suppression of the radiation
emitted by high-energy particles in an infinite amorphous medium, but certain differences do exist. On the basis of our approach
we analyze the data recently obtained at SLAC (E-146) in experiments set up to verify the LPM effect. We show that in addition
to the LPM effect, this experiment exhibited the suppression of bremsstrahlung in a thin layer of matter, theoretically predicted
in our earlier papers.
Zh. éksp. Teor. Fiz. 113, 58–70 (January 1998) 相似文献
10.
11.
V. P. Silin 《JETP Letters》1998,67(5):329-333
The polarization of the high harmonics generated in plasmas by the bremsstrahlung of electrons oscillating under the influence
of high-power plasma-heating electromagnetic radiation is described on the basis of a simple model of a cold plasma. It is
shown that when the polarization of the heating radiation differs from plane polarization by a small but finite amount, the
high harmonics are generated with almost perpendicular polarization, and the degree of circular polarization of the harmonics
increases with the number of the harmonic.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 5, 313–316 (10 March 1998) 相似文献
12.
V. A. Astapenko 《Journal of Experimental and Theoretical Physics》1999,88(5):889-894
The polarization dependence of the stimulated bremsstrahlung and inverse bremsstrahlung (SBIB) of quasiclassical electrons
on highly charged ions with a core is calculated in the approximation of a specified Coulomb current. Emission frequencies
close to an eigenfrequency of the ion core are considered. The contributions of the static and polarization channels are taken
into account in the amplitude of the process. When the nondipole nature of the interaction between the incident particle and
a resonant transition in the ion core is taken into account, interference between these channels causes the spectral-amplitude
characteristics of the process to assume a specific dependence on the angle α between the electric field intensity vector of the electromagnetic wave and the initial velocity vector of the incident particle.
This dependence, which persists after integration of the cross section over the scattering angle of the incident particle,
causes interference effects, viz., asymmetry of the line shape and dips in the dependence of the SBIB cross section on electric
field intensity, to appear for α=π/2 and significantly reduces them for α=0.
Zh. éksp. Teor. Fiz. 115, 1619–1629 (May 1999) 相似文献
13.
This paper presents, for the general relativistic case, a theoretical study of nonresonance spontaneous bremsstrahlung by
an electron scattered by a nucleus in the field of two elliptically polarized light waves propagating in the same direction.
We show that there are two significantly different kinematic regions: the noninterference region where the main multiphoton
parameters are the Bunkin-Fedorov quantum parameters γ
1,2, and the interference region where interference effects play an important role and where the quantum interference parameters
α(±) act as multiphoton parameters. We encounter the spontaneous interference bremsstrahlung effect in two cases: in the special
case of the same linear polarization of both waves, and in the general case of elliptical polarization of the waves. The effect
manifests itself in the interference region and is due to stimulated, correlated emission and absorption of photons of both
waves. For moderately strong fields, we find the cross sections of spontaneous bremsstrahlung by an electron scattered by
a nucleus in the given kinematic regions. Finally, we show that the differential cross section in the interference region
with correlated emission (absorption) of equal numbers of photons of both waves can be much greater than the corresponding
cross section in any other geometry.
Zh. éksp. Teor. Fiz. 116, 1210–1240 (October 1999) 相似文献
14.
A. V. Maksimov K. N. Ovchinnikov V. P. Silin S. A. Uryupin 《Journal of Experimental and Theoretical Physics》1998,86(4):710-716
In this paper we evaluate theoretically the modification of the distribution function of slow subthermal electrons heated
by radiation in a completely ionized plasma. The new solution we have found to the kinetic equation under conditions typical
of weak-collisional plasmas can be used to predict new nonlinear behavior arising from perturbations of the nonuniform electron
density and the coefficient of nonlocal heat transfer that depend on the intensity of the radiation heating the plasma, which
is absorbed via inverse bremsstrahlung. It is predicted that this new nonlinear behavior manifests itself at unexpectedly
small radiation intensities.
Zh. éksp. Teor. Fiz. 113, 1299–1312 (April 1998) 相似文献
15.
Yu. K. Zemtsov A. Yu. Sechin A. N. Starostin A. G. Leonov A. A. Rudenko D. I. Chekhov 《Journal of Experimental and Theoretical Physics》1998,87(1):76-86
The purely thermal visible and infrared radiation emitted by a dense resonant medium (sodium vapor) heated nonuniformly to
temperatures of 600–1200 K was investigated experimentally for the first time under conditions where the photon mean free
path is comparable with the emission wavelength. The profile of the recorded spectra and the absolute luminescence intensities
in the different spectral ranges show good agreement with the results of a numerical simulation using a previously developed
theory of resonance radiation transport which assumes a Boltzmann spectral distribution of the resonant level population proportional
to exp(−ℏω/T). The self-reversed resonant sodium line exhibited strong asymmetry and it was shown that under certain conditions, the luminescence
spectrum of the medium may exhibit an additional broad peak on the far “red” limb of the resonance line. Calculations and
measurements demonstrated that the intensity of the thermal emission of sodium vapor at this red peak is several orders of
magnitude higher than that obtained from the standard theory of resonance radiation transport. This effect is arbitrarily
termed an infrared “ catastrophe.” It is noted that in a solar corona plasma and in gas-discharge lamps, the far red limbs
of the resonant lines may make a substantial contribution to the total luminescence intensity and in some cases, considerably
exceed the intensity of the photorecombination and bremsstrahlung continuum.
Zh. éksp. Teor. Fiz. 114, 135–154 (July 1998) 相似文献
16.
Yu. K. Zemtsov A. Yu. Sechin A. N. Starostin A. G. Leonov D. I. Chekhov 《JETP Letters》1997,65(11):839-844
The purely thermal infrared emission spectra of a resonance medium (sodium vapor) are investigated experimentally. It is shown
that the emission intensity in the 2–3 μm range at temperatures of 600–1200 K is several orders of magnitude higher than the
intensity obtained from the standard theory of resonance radiation transfer. This phenomenon can be conventionally termed
an “infrared catastrophe.” The form of the recorded spectra and the absolute intensity of the emission in both the infrared
and visible regions of the spectrum are in agreement with the theory developed by Yu. L. Zemtsov and A. M. Starostin, Zh.
éksp. Teor. Fiz. 103, 345 (1993) [JETP 76, 186 (1993)], in which the Boltzmann spectral distribution of the population of the resonance level is proportional to exp(−ħω/T).
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 11, 807–811 (10 June 1997) 相似文献
17.
A. P. Sebedash 《JETP Letters》1997,65(3):276-281
A new method of pressure regularization in the measuring cell is proposed for experiments on self-cooling of weak solutions.
Preliminary results are presented for solutions with concentrations of 2% and 7%. Cooling by a factor of 1.5–2 was observed
in the starting-temperature range 40–140 mK.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 3, 263–267 (10 February 1997) 相似文献
18.
We have obtained macroscopic fractal aggregates of fullerite ranging in size from 100 to 400 μm. The fractal structure of
fullerite is formed by microscopic (30–100 nm) fullerite crystals in the presence of a temperature gradient under conditions
of diffusion-limited aggregation.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 9, 684–685 (10 May 1998) 相似文献
19.
Giant (up to 68%) room-temperature magnetoresistance is observed in (110) V films on mica with a periodic system of 5–25 nm
wide, thin (⩽10 nm) Co strips, separated by 1–2 nm gaps, grown on the films. The effect is observed only for samples in which
the magnetization tilts out of the plane of the film.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 5, 346–349 (10 September 1996) 相似文献
20.
A. G. Leonov D. I. Chekhov A. N. Starostin 《Journal of Experimental and Theoretical Physics》1997,84(4):703-715
An experimental investigation and numerical simulation of resonant laser breakdown are performed. As a result, quantitative
agreement between the experimental data on the parameters of a dense resonant plasma (the electron density and the electron
temperature) and the results of calculations in the range of detunings of the laser radiation from resonance Δλ>2–2.5 nm, in which the spatial instability of the intense resonant laser beam and the absorption of radiation are minimal,
is obtained for the first time. It is shown that the previously proposed mechanism of resonant breakdown associated with laser-induced
associative ionization introduces only a small correction to the final extent of ionization of the resonant plasma and scarcely
alters its temperature. The influence of quantum stimulated inverse bremsstrahlung processes, which are usually described
as collisions of the second kind in the resonance case, on the energy gain by electrons is analyzed for the first time in
reference to specific experimental findings. The numerical calculations show that at detunings of the order of the Rabi frequency,
the mechanism by which electrons gain energy through the resonant system does not reduce to collisions of the second kind
and can significantly increase the density of the resonant plasma. However, in this range of detunings the laser beam is still
strongly perturbed by instability processes, precluding a proper comparison of the theory with experiment. At large Δλ the classical and quantum cases differ from one another only slightly, and the values of N
e calculated for both mechanisms lie within the measurement error.
Zh. éksp. Teor. Fiz. 111, 1274–1296 (April 1997) 相似文献