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1.
A compact expression is derived for the part of the cross section for light scattering by axisymmetrically polarized atomic systems proportional to the third-rank state multipole. The effect of the second-order orientation determined by this state multipole on the polarization and angular distribution of the scattered light is studied. The polarization of the incident light can be arbitrary and is specified by the Stokes parameters. A number of orientation effects in the scattering process are shown to be induced precisely by the second-order orientation. In particular, when nonpolarized light is scattered by an oriented atom, the scattering intensity in the perpendicular direction depends on the second-order orientation alone. The second-order orientation also preserves circular dichroism in the linear polarization of the forward-and back-scattered light.  相似文献   

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The multichannel diffraction approximation is used to consider excitation of lithium atom by proton and antiproton impact. The sign-of-charge effect in the alignment of produced 1s23d excited state and in the linear polarization of the subsequent spontaneous 1s23d→1s22p radiation is expected to be considerable.  相似文献   

4.
An expression for the cross section of light scattering by axisymmetrically aligned atomic systems is derived in a compact form. The cross section under consideration is proportional to the state multipole of the fourth rank. The effect of the second-order alignment determined by the fourth-rank state multipole on the polarization and the angular distribution of scattered light is investigated. The polarization of incident light can be arbitrary and, in the general case, is specified by the Stokes parameters. In particular, it is demonstrated that the second-order alignment cannot induce circular polarization of scattered light and does not influence the dissipation-induced effects of circular dichroism associated with the first-order alignment but leads to a change in the angular distribution and the degree of linear polarization of the scattered light.  相似文献   

5.
Scattering of a resonance electromagnetic field from excited atoms cannot be described by the semiclassical theory of radiation operating with nonquantized electromagnetic fields. Field quantization effects are manifested in this case on the macroscopic level and lead to evolution of statistical properties of radiation in the course of scattering. It is found that a combined process coupling elastic scattering from an atom and induced emission from the same atom, which cannot be studied by the methods of the standard perturbation theory, plays a significant role in this effect. The process of combined scattering in extended media exhibits coherent properties that cannot be described by the standard refractive index.  相似文献   

6.
The properties of the collision integral in a quantum Boltzmann-type kinetic equation are studied under the conditions of spatially nonuniform distributions of colliding particles interacting with an external electromagnetic field. The components of the nonlinear resonances and the velocity distribution of the excited atoms, which are due to polarization transitions, are determined on the basis of the Kazantsev collision integral.  相似文献   

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On the basis of the quantum theory of radiation, we study the characteristics of forward transition radiation not predicted by the semiclassical radiation theory (which uses a nonquantized electromagnetic field) and not described by the index of refraction of the medium.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 57–61, February,1986.The author thanks the participants of a seminar conducted by V. L. Bonch-Bruevich for useful discussions.  相似文献   

9.
Luminescence spectroscopy with subnanosecond time resolution is used to study features of nonequilibrium processes excited in several broad-zone dielectrics (mainly inorganic scintillators) by pulses of synchrotron radiation (SR). When excitation density exceeds a certain level, which is different for each material, there is an abrupt change in the kinetics of relaxation of the nonequilibrium states. This change is accompanied by nonuniform broadening or shortwave shifting of the luminescence spectrum and a drop in quantum light yield. The decay time for natural luminescence decreases by 1–3 orders, to nanoseconds, and is independent of temperature within the range 80–450 K. The build-up stage disappears in the kinetics of luminescence of Ce3+-centers and decay time is reduced by a factor of 2–4. Density effects are found to be independent of the conditions under which the material is exposed to SR. A model is proposed in which density effects are related to nonradiative energy transfer from the upper excited states of the luminescence centers to external quenching centers. The contribution of the space charge induced by SR is also examined. Ural State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 120–135, November, 1996.  相似文献   

10.
A general approach to the problem of spontaneous transfer of light-induced anisotropy in the scheme of Raman scattering of resonance elliptically polarized light is developed. Depending on the type of the field-excited (a)?(b) transition, the stationary distribution of atoms over the sublevels of the final level (c) coupled with the excited level only by the (b)→(c) spontaneous transition is either isotropic and does not depend on field parameters or anisotropic. In the latter case, the anisotropy is determined by both field polarization and (at fairly large level momentum values) field detuning and intensity.  相似文献   

11.
By photon absorption from a monomode dye-laser beam a spatially ordered velocity distribution (‘atomic beam’) of sodium atoms excited to the 3p 2 P 1/2-state, is created. It is predicted theoretically that in collisions of these atoms with atoms of a heavy foreign gas an alignment of the electronic orbital angular momentum is produced. This alignment leads to the appearance of a linear polarization in the sensitizedD 2-fluorescent light. This polarization is verified experimentally and interpreted in terms of a simplifiedT-operator. It turns out that the scattering distribution for sensitizing collision is of the wide-angle type.  相似文献   

12.
Two-photon ionization of the hydrogen-like uranium ion by elliptically polarized radiation is investigated in the present work. It is demonstrated that the fundamental effect of interference of the probability amplitudes arises in the angular photoelectron distribution when the degree of ellipticity of ionizing radiation is varied. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 39–41, December, 2008.  相似文献   

13.
It is shown that, with pumping inclined relative to a constant magnetic field H0, the radio-frequency (RF) magnetic field rotating at frequency Ω induces new resonances ω0 = γ H 0 and 2Ω for the Fourier components of orientation and ω0 = ?Ω, Ω/2, 3Ω/2, 2Ω, and 3Ω for the components of alignment. New resonances excited by the oscillating RF field are also considered.  相似文献   

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Cyclic interaction of Na atoms with laser radiation is under consideration. In the experiment cyclic interaction was conducted through preliminary optical pumping of the atom into the ground state F = 2, MF = 2 by a single-mode cw dye laser. The results of optical orientation of Na atom and cyclic interaction under different conditions of atomic excitation are presented. Possible applications of cyclic interaction of atom with radiation for detection and cooling of atoms is under discussion.  相似文献   

16.
We have measured the polarization of light emitted in optical transitions in P V, O VII and O VIII, produced by beam foil excitation, using a 400 keV phosphorus beam from a heavy ion accelerator and a 36 MeV oxygen beam from a Tandem Van de Graaff generator.  相似文献   

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A system for the acquisition of angle-resolved photoelectron spectra is described. The sample gas is excited by VUV resonance radiation, which is polarized to about 95% using a fully rotatable fourfold reflection polarizer. One of the mirrors is toroidally shaped in order to focus the radiation into the sample gas cell. This design gives count rates comparable to those obtained by an unpolarized source, and at a greatly reduced background level. A computer controlled system has been developed to automate the recording procedure. It allows for simultaneous recordings of the spectra at the different angular settings, thus eliminating the effects of intensity drifts. Details of calibration procedures and data processing, including spectrum analysis, are given along with a discussion of the accuracy of the results. To illustrate the performance, measured β-values for the main components of the four outermost photoelectron bands in the Hel excited spectrum of CO2 are presented.  相似文献   

19.
In this Letter, we study the molecular alignment and orientation driven by two elliptically polarized laser pulses.It is shown that the field-free molecular alignment can be achieved in a three-dimensional(3D) case, while the field-free molecular orientation is only along the x and y directions, and that the field-free alignment and orientation along different axes are related to the populations of the rotational states. It is demonstrated that changing the elliptic parameter is efficient for controlling both in-pulse and post-pulse molecular alignment and orientation. The delay time also has an influence on the field-free molecular alignment and orientation.  相似文献   

20.
A number of processes in which highly excited states of atoms and molecules participate are investigated. These processes are of interest for the kinetics of a low-temperature plasma, for atomic and molecular spectroscopy, and for astrophysics. A quasiclassical theory is developed for transitions between Rydberg states with change of the principal quantum number, and also for the processes of direct and associative ionization of highly excited atoms, which result from collisions between a neutral particle and its atomic core. The state of the inner electrons of a quasimolecular (molecular) ion is not altered by transitions of the outer electrons. Specific calculations are carried out for the case of the collision of hydrogen H(n) with helium He (1s2) atoms. It is shown that the cross sections and the rate constants of these processes are determined in this case by the mechanism investigated in the paper, and not by scattering of the Rydberg electron by the neutral particle. The cross sections for dipole excitation and dissociation of molecular ions from high vibrational energy levels by electron impact is calculated in the Born-Coulomb approximation. The cross sections and the rates of dissociative and three-particle attachment of electrons to ions are determined. The processes of autoionization and autodissociation decay of Rydberg states of vibrationally excited molecules are determined. Also investigated are radiative transitions near the dissociation limit of diatomic molecular ions and neutral molecules, viz., photodissociation and radiative decay of high vibrational levels, and photodissociation and translational (inverse-bremsstrahlung) absorption in collision of atomic particles.Translated from Trudy Ordena Lenina Fizicheskogo Instituta im. P. Lebedeva AN SSSR, Vol. 145, pp. 80–130, 1984.  相似文献   

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