Reflection of narrow light beams by a scattering medium

A calculation is made of the doubly back scattered radiation from the intersection volume and the close-range volume. A comparison of the results for singly and doubly scattered radiation with experimental data enables the limits of applicability of the equations to be determined. It is shown that for scattering coefficients in fog of < 0.06 m^–1 the scattered radiation field is caused by single scattering but when increases to 0.6 m^–1 only the doubly scattered radiation from the intersection and close-range volumes need be considered.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 95–100, April, 1974.     

An anomalous correlator of resonantly scattered light

The space-time properties of the correlator of the light intensities scattered from resonant atoms are studied. It is shown that in measuring such a correlator by the method of optical shifts, an appreciable contribution appears from the anomalous correlator of the scattered field amplitudes. It is simple to observe this correlator in the field of a standing wave by measuring the correlation of oppositely scattered rays. The spectral and polarization properties of such a correlator are studied. Its investigation is of interest for high-resolution spectroscopy because it allows information to be obtained on the natural width of a line in conditions of strong Doppler broadening. It is important to stress that this is possible in a linear approximation with respect to the strength of the external field in contrast to the methods of laser spectroscopy based on nonlinear effects.     

Looking at saturation effects with production in pA collisions

We compute the inclusive differential cross section production of the pseudo-scalar meson η^′ in high-energy proton-nucleus (pA) collisions. We use an effective coupling between gluons and η^′ meson to derive a reduction formula that relates the η^′ production to a field-strength tensor correlator. We take into account saturation effects on the nucleus side by using the Color Glass Condensate formalism to evaluate this correlator. We derive new results for Wilson line - color charges correlators in the McLerran-Venugopalan model needed in the computation of η^′ production. The unintegrated parton distribution functions are used to characterize the gluon distribution inside the proton. We show that the cross section is sensitive to saturation effects so it can be utilized to estimate the value of the saturation scale.     

An interpolation of the vacuum polarization function for the evaluation of hadronic contributions to the muon anomalous magnetic moment

We propose a simple parameterization of the two-point correlator of hadronic electromagnetic currents for the evaluation of the hadronic contributions to the muon anomalous magnetic moment. The parameterization is explicitly done in the Euclidean domain. The model function contains a phenomenological parameter which provides an infrared cutoff to guarantee the smooth behavior of the correlator at the origin in accordance with experimental data in e ⁺e^- annihilation. After fixing a numerical value for this parameter from the leading order hadronic contribution to the muon anomalous magnetic moment, the next-to-leading order results related to the vacuum polarization function are accurately reproduced. The properties of the four-point correlator of hadronic electromagnetic currents as for instance the so-called light-by-light scattering amplitude relevant for the calculation of the muon anomalous magnetic moment are briefly discussed. Received: 14 December 2001 / Published online: 7 June 2002     

On the electrical conductivity of intermediate valence compounds

The electrical resistivity of the hybridized 4f-(5d/6s) system interacting with LA phonons is calculated by applying the memory function method to the periodic Anderson model in Hartree-Fock approximation. We propose a new mechanism to explain in part the anomalous resistivity of mixed valence compounds such as CePd₃. For finite hybridizationV a finite fraction of 4f electrons participates in electrical conduction leading to an essential change of the normald band current. Resistivity and the fraction of 4f electrons increase with increasing value of [V/(E–)]² where (E–) is the distance between the effective positionE of the 4f level and the chemical potential. In typical mixed valence systems [V/(E–)]² is strongly temperature dependent and decreases with increasing temperature. This explains the high temperature resistivity behaviour of CePd₃. For (E–) being small compared to the Debye-temperature the resistivity is enhanced and becomes extremely sensitive to small changes of (E–).Work performed within the research program of the Sonderforschungsbereich 125, Aachen-Jülich-Köln     

Spatial and Angular Characteristics of the Atmospheric Showers Initiated by Photons of Energy E γ = 1018–1022 eV in the Magnetosphere of the Earth

Spatial-angular characteristics are calculated for the atmospheric electromagnetic showers generated by primary photons of ultrahigh energies (E = 10¹⁸–10²² eV) coming from outer space. Calculations carried out for vertical and oblique showers in view of the interaction of photons and electrons with the dipole magnetic field of the Earth (formation of electron-positron pairs, synchrotron radiation) and taking into account the Landau–Pomeranchuk–Migdal effect in the processes of interaction of electrons and photons with matter in the meteorological atmosphere.     

Quadrupole interaction studies of Hg in Sb

Time differential perturbed angular correlation and nuclear orientation studies of the electric quadrupole interaction for Hg in Sb have been performed. The effective field gradients |V _zz ^eff (HgSb)|=1.43(18)×10¹⁷V cm^–2 at room temperature andV _zz ^eff (HgSb)=+1.8(2) × 10¹⁷V cm^–2 below 0.05 K have been derived. These two values are no indication for an anomalous temperature dependence of the effective field gradient for Hg in Sb. The value of the electric field gradient fits well into the systematics for Hg in other hosts. It is shown that the electronic enhancements of the field gradients are correlated to the valence of the impurities and are rather insensitive to the host properties.On leave of absence from: University of Lisboa, Portugal     

Change in the magnetoresistance of n-GaAs in an electric field

The effect of an electric field on the magnitude of the magnetoresistance in epitaxial n-GaAs films with free carrier concentrations n_e=4.0.10¹⁵–1.12. 10¹⁶ cm^–3 at T=4.2K was investigated. It was found that in weak electric and magnetic fields for E < E_b (E_b is the intensity of the low-temperature impurity breakdown field) the magnetoresistance (MR) is negative, and for EE_b only a positive magnetoresistance is observed. The experimental results are explained by a change in the concentration of centers with a magnetic moment and of electrons in the impurity band in prebreakdown electric fields.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 51–55, July, 1981.     

Reflection of narrow light beams by a dissipating medium

The brightness distribution of multiple back-scattering of radiation is investigated in a plane perpendicular to the beam axis as a function of the density of the artificial mists and smokes. The range of the distances from the beam axis (base) investigated was 0.02–1 m or 10^–4–1.8 in optical quantities. The investigations were accompanied by parallel measurements of the scattering index by using a turbidimeter, which permitted making quantitative estimates of the influence of the form of the index on the magnitude of the intensity of the multiply-scattered radiation for diverse values of the optical base. It is shown that the brightness distribution of the multiply scattered radiation takes on a smoother shape as the elongation of the index increases.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 61–65, November, 1973.     

Dynamic theory of two-photon correlators in the spectroscopy of single impurity centers

A dynamic theory of two-photon correlators measured in experiments with single molecular impurity centers has been developed. The theory takes into account the interaction between optically active electrons of an impurity center and phonons, excitations in tunneling systems of polymers and glasses, and transverse electromagnetic field. Both the correlator measured in the start-stop regime and the “full” correlator have been analyzed, and equations for these correlators have been derived. An equation relating these two correlators has been also obtained. The effect of the triplet level of an impurity molecule on the correlators leading to bunching of spontaneously emitted photons has been studied. The two-photon correlators have been calculated numerically, and their dependence on the incident light frequency and time between the pairs of detected photons in various realistic situations has been derived. Zh. éksp. Teor. Fiz. 113, 1606–1631 (May 1998)     

Frequency Dependence of the Components of Dielectric Permeability and Characteristic Losses of Fluorite

The ₁(E), –Im^–1, and Re^–1 spectra of the fluorite crystal are calculated on the basis of the experimental (10–35 eV) and theoretical spectra ₂(E) (10–27 and 8–20 eV). They were employed to decompose the ₂(E) and –Im^–1 spectra into elementary components. The most intense transverse and longitudinal components of transitions and their parameters have been determined. The correlation between two types of components of transitions and their distinguishing features have been established.     

Electrical and optical properties of electron-irradiated ZnGeP2

Conclusions and summary The following conclusions are drawn from the reported study:The electrophysical properties of ZnGeP₂ crystals and their optical transparency in the range hG are attributable to the presence of a density-dominant (10¹⁷–10¹⁹ cm^–3) deep [E_v+(0.5–0.6) eV] growth defect associated predominantly with Zn vacancy clusters.Irradiation by high-energy electrons induces a shift of the Fermi level in the direction of E_G/2 and increases the resistivity of ZnGeP₂ to values of approximately 10¹² ·cm at 300 K. Irradiation with high-energy electrons is an effective technique for the optical bleaching of p-ZnGeP₂. The reversible modification of the optical absorption spectra of p-ZnGeP₂ in connection with irradiation and subsequent annealing indicates that the absorption step in the vicinity of h 0.6 eV is not attributable to light absorption by germanium inclusions, but to optical transition from the valence band to the growth-defect level E_v+(0.5–0.6) eV.Enhancement of the optical transmissivity of p-ZnGeP₂ in the range hG can be achieved in two wayss 1) as the result of a decrease in the density of centers with the level E_v+0.6 eV by variation of the growth conditions or subsequent annealing; 2) by shifting the Fermi level above the energy position E_v+0.6 eV through the irradiation-induced injection of compensating donor centers.The injection of radiation defects is an effective technique for controlling the electrical and optical parameters of the compound ZnGeP₂.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 122–130, August, 1986.     

Monte Carlo simulation of spin-aligned atomic hydrogen

The density dependent ground-state properties of spin-aligned atomic hydrogen are studied using the Monte Carlo technique for 32 and 128 atoms in a cube with periodic boundary conditions. The one-particle density matrix, the two-body correlation function, the structure and pairing function have been evaluated and are compared to other recent work. The total number of particles in the condensate is largest at a density 6·10^–3 Å^–3 and amounts to ⁰=2.03·10^–3Å^–3. In addition, the elementary excitation spectrum is discussed in the framework of the Brueckner-Sawada theory. The correct initial slope of the spectrum is obtained from variational results on the structure function. From these results one may tentatively conclude that the roton like part of the spectrum disappears at densities less than 10^–2 Å^–3.     

Anticommutativity equation in topological quantum mechanics

We consider topological quantum mechanics as an example of topological field theory and show that its special properties lead to numerous interesting relations for topological correlators in this theory. We prove that the generating function ? for these correlators satisfies the anticommutativity equation (D?F)². We show that the commutativity equation [dB, dB]=0 can be considered as a special case of the anticommutativity equation.     

Heavy-to-light correlators beyond the light cone

We present the first systematic analysis of the off-light-cone effects in correlators relevant for the extraction of the heavy-to-light form factors within the method of light-cone sum rules. In a model with scalar constituents, the correlator is calculated in two different ways: (i) by performing the expansion of the Bethe-Salpeter amplitude of the light meson near the light cone x ² = 0 and (ii) by adopting the known solution for the Bethe-Salpeter amplitude which allows one to calculate the correlator without invoking any expansion. We demonstrate that the contributions to the correlator from the off-light-cone terms x ² ≠ 0 are not suppressed by any large parameter compared to the contribution of the light-cone term x ² = 0. For decays of heavy particles of mass in the range 1.5–5 GeV, the light-cone correlator is shown to systematically overestimate the full correlator, numerically the difference being 10–20%. The text was submitted by the authors in English.     

Spatial distribution of albedo particles on altitudes ∼500 km

Spatial distributions of energetic charged particles, neutrons and gamma rays at altitude 500 km (below the radiation belts of the Earth), obtained by the measurements of two apparatuses on board the Intercosmos-17 satellite, are presented. The latitudinal dependences, [i.e. the variation of flux with vertical cut-off rigidity of the measurement point], for neutrons (E _n = 1 –30 MeV), gamma rays (E =0·15–6 MeV), secondary electrons (E _e > 100 MeV) and for primary protons coming from the west and the east, respectively, are given. The main characteristic, the ratioN _p/N _e of the counting rate of the particles in the polar regionN _p(R_vert< <0·1 GeV/c) and on the equatorN _e(R_vert > 16 GeV/c), is obtained for the various types of particles. This value is 10 for neutrons, 3.7 for gamma rays, 1·8 for electrons, 11 for protons in westward direction, 10 for protons in eastward direction. The latitude profile of neutrons and gamma rays is in a good agreement with calculations assuming their production by nuclear reactions of primary cosmic rays with nuclei of the atmosphere. The weakening of rigidity dependence of protons coming from east in comparison with those coming from the west, is interpreted as the cause of additional proton albedo flux. The equality of albedo electron fluxes (E_e = 100–3500 MeV) from these directions is observed. With the use of the shadowing effect the obtained data on electron-positron component are consistent with the flux of albedo positrons (E_e + > 3·5 GeV) of the value (0·5±0·2) m^–2. s^–1. ster^–1. The possibility of abundance of albedo positrons above electrons at these altitudes for the energy intervalE=0·2÷0·3 GeV is indicated.     

Colormagnetic confinement in the quark–gluon thermodynamics

Nonperturbative effects in the quark–gluon thermodynamics are studied in the framework of vacuum correlator method. It is shown, that for T > T ₀ = 175 MeV two correlators: colorelectric D ₁ ^E (x) and colormagnetic D ^H (x), provide the Polyakov line and the colormagnetic confinement in the spatial planes respectively. As a result, both effects produce the realistic behavior of p(T) and I(T), being in good agreement with numerical lattice data.     

Intensity of x-ray solar radiation and the value of the anomalous absorption of radio waves during periods of sudden ionospheric disturbances

An experimental statistical dependence is obtained between the intensity of the x-ray radiation of the sun in the range 1–8 å (I_1–8) and the value of the anomalous absorption of radio waves at a frequency of I=13 MHz during periods of sudden ionospheric disturbances. This dependence has the form ₁₃ I _1–8 ^0.8 cos , and can be used for the operative classification of bursts of x-ray radiation. Its character is explained by a decrease in the coefficient of the losses of electrons with a rise in the intensity of the x-ray radiation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 21, No. 11, pp. 1558–1562, November, 1978.I wish to thank E. A. Benediktov and V. V. Belikovich for their interest in the work and their critical evaluation of its results.     

Time and temperature dependent breakdown characteristics of ZnS:Mn films obtained by rf-magnetron sputtering

Breakdown delay times (t_del) for films of managanese-doped zinc sulfide (ZnS:Mn) were measured in the range 10^–6–10^–1 s. The maximum value was t_del=10^–3–10^–2 s. The electrical strength (E_br) was found to increase as the voltage pulse duration was reduced, the more so the thinner the ZnS:Mn film. The temperature dependence of E_br exhibited a weak reduction in E_br as the temperature was raised to roughly 80°C and a sharp reduction in E_br for T>130°C. A maximum in E_br was observed at T130°C which is presumably explained by a structural modification of the ZnS:Mn film. The experimental results obtained are explained in terms of a combined electronic and thermal breakdown mechanism.State Academy of Control Systems and Radioelectronics, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 3–6, April, 1994.     

Selectively dopedn-AlxGa1−xAs/GaAs heterostructures with high-mobility two-dimensional electron gas for field effect transistors

The transport properties of warm and hot electrons in selectively dopedn-Al _x Ga_1–x As/GaAs heterostructures created by electric fields up to 500 V/cm were studied by Hall effect, conductivity, and Shubnikov-de Haas measurements at lattice temperatures from 4.2 to 300 K. Hall measurements revealed a substantial decrease of electron mobility and also of sheet electron concentration at 77 K with enhanced electric field. The accelerated 2D electrons are partly scattered into the low-mobility first excited (E ₁) subband, and they are partly trapped in immobile states located in the Al_xGa_1–xAs near the interface. Consequently, two differentv(E) characteristics were obtained at 77 K. The 2D electrons populating only the lowest (E ₀) subband exhibit a velocity of v-2×10⁷ cm/s at 500 V/cm, while the averaged velocity due to all electrons reaches a value of v-1.5×10⁷cm/s at 500 V/cm. The analysis of the Shubnikov-de Haas oscillations and Fast Fourier transformation of the data manifested that the 2D electrons are very rapidly accelerated at 4.2 K and achieve electron temperatures much higher than the lattice temperature at electric fields as low as 1 V/cm. The major cooling process for these electrons is scattering into the low-mobilityE ₁ subband.