Application of relativistic Coulomb Green's function to the calculation of transition probabilities in an electric field

The probability of transitions between the levels of multiply charged ions in a strong electric field are expressed in terms of the matrix elements of the relativistic Coulomb Green's function. The probability of magnetic dipole decay of the 2s1/2 level of a hydrogenlike ion in a field F=10⁷ V/cm is calculated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 38–42, February, 1981.I should like to express my thanks to Professor L. N. Labzovskii for numerous discussions and valuable comments.     

Large field permittivity of TGS at 20 kHz

The paper gives the results of complex permittivity measurements of triglycine sulphate at large electric field amplitudes (36.6 V/m–386 kV/m) and a frequency of 20 kHz in a temperature range including the Curie temperature (22–53°C). An experimental arrangement for measuring by means of the pulse method is described which was used in order to prevent heating of the sample due to dielectric losses. The relations established between the permittivity and the amplitude of the electric field and temperature are in good qualitative agreement with the corresponding results obtained by calculation in the paper of J. Fousek [J. Appl. Phys. 36 (1965), 588].The authors are indebted to Dr. Z. Málek, Dr. J. Fousek, Ing. J. Janta, M. Marvan, Ing. J. Mastner and J. Fiala for valuable discussions and comments, to Ing. Z. Vojta for his help in realizing the electronic apparatus and to K. Müller for the careful preparation of the figures for publication.     

Radiation of fermions with anomalous moments in an electric field

The radiation of Fermi particles in an electric field is calculated under the assumption that the particles have an electric moment, which, like an anomalous magnetic moment, is taken into account phenomenologically. It is shown that if Fermi particles have an electric moment there may be a preferred spin orientation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 26–31, August, 1980.We thank V. G. Bagrov for numerous and very helpful discussions on these questions, and also V. I. Ritus and I. V. Tyutin for discussing the results.     

Critical character of gravitational-wave modulation of electric and magnetic fields in isotropic media

The exactly integrable model of the evolution of electric and magnetic fields in an isotropic dielectric medium under the action of gravitational radiation is analyzed. It is shown that as a result of the action of the gravitational radiation field, the dynamic characteristics of an electromagnetic field as a function of the dielectric constant lose continuity in a neighborhood of the value n=1.V. I. Ul'yanov Lenin Kazan' State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 28–33, September, 1993.     

Multiphonon hopping in disordered semiconductors

Equations of motion for the nonequilibrium single-frequency density matrix are used to obtain a balance equation describing the kinetics of electron hopping between localized states in disordered semiconductors. Conclusions are drawn about the applicability of the theory of multiphonon processes to systems with a small nonadiabaticity. The decoupling used is a generalization of one used earlier to the multiphonon case. The balance equation found in the Markov approximation for the average number of sites occupied in an electric field contains the field dependence of the multiphonon-transition probability, tending to the well-known weak-field limit.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No.2, pp.35–42, February, 1976.In conclusion the author is grateful to V. L. Bonch-Bruevich and A. G. Mironov for discussing this work.     

Trap ionization in phosphors in a strong electric field

Temperature dependences of the intensity of Gudden-Pohl flashes in zinc sulfide crystals in various electric fields were measured in order to study trap ionization by electric fields. The decrease in the flash intensity from trap levels of a given depth in a certain temperature range is due to a decrease in the probability for the liberation of an electron from a trap as the temperature decreases. The temperature dependences of the flash intensity found in various electric fields are compared with the theoretical temperature dependence of the probability for electron liberation from a trap. The agreement between experimental and theoretical curves indicates that electrons are liberated from the deeper levels through ionization by an electric field involving many phonons.Translated from Izvestiya VUZ. Fizika, No. 10, pp. 53–58, October, 1969.     

Sharp increase in mobility of spiral dislocations by a pulsed electric field

An investigation is made of the change in expansion rate V of spiral dislocational half-loops in NaCl crystals after brief application of an electric field. It is established that, after the application of a field pulse at fixed shear stress, V rises sharply at first and then, with time, falls exponentially to its initial value. The initial increase in V depends on the amplitude of the electric pulse, and the relaxation time of its subsequent fall on the temperature. The activation energy of the process is determined from the temperature dependence of the relaxation time.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 71–74, March, 1979.     

Structural investigations of the ionic conductivity in zirconia single crystals by neutron diffraction at high temperatures and simultaneously applied electric field

In situ neutron diffraction studies of CaO and Y₂O₃ stabilized zirconia single crystals were performed at elevated temperatures and simultaneously applied DC electric field, i.e. lasting ionic current. Bragg data from Zr_0.85Ca_0.15O_1.85 (CSZ15) were collected at room temperature without electric field, at 1170 K and 1370 K without and with 3.5 V and 1.8 V, respectively, (field vector Ell[111]), which generated a current of 60 mA in each case. In case of Zr_0.70Y_0.30O_1.85 (YSZ15) the electric field vector was directed along [001]. At 1170 K three data sets were collected: without field, with 1.5 V (I=60 mA), and with 2.5 V (I=120 mA). Atomic displacement parameters (a.d.p.'s) were derived in the frame of a non-Gaussian Debye-Waller factor formalism for the oxygens. Corresponding probability density function (p.d.f.) maps and pseudo potential maps were calculated. Most probable curved diffusion pathways run close to 〈 100 〉, independent of the external field direction, applied voltage and the kind of dopant. With lasting ionic current the potential corresponding to p.d.f. >1% is lowered by about 0.06–0.07 eV.     

An AlGaN/GaN HEMT with a reduced surface electric field and an improved breakdown voltage

A reduced surface electric field in an AlGaN/GaN high electron mobility transistor(HEMT) is investigated by employing a localized Mg-doped layer under the two-dimensional electron gas(2-DEG) channel as an electric field shaping layer.The electric field strength around the gate edge is effectively relieved and the surface electric field is distributed evenly as compared with those of HEMTs with conventional source-connected field plate and double field plate structures with the same device physical dimensions.Compared with the HEMTs with conventional sourceconnected field plates and double field plates,the HEMT with a Mg-doped layer also shows that the breakdown location shifts from the surface of the gate edge to the bulk Mg-doped layer edge.By optimizing both the length of Mg-doped layer,L m,and the doping concentration,a 5.5 times and 3 times the reduction in the peak electric field near the drain side gate edge is observed as compared with those of the HEMTs with source-connected field plate structure and double field plate structure,respectively.In a device with V GS = -5 V,L m = 1.5 μm,a peak Mg doping concentration of 8×10 17cm-3 and a drift region length of 10 μm,the breakdown voltage is observed to increase from 560 V in a conventional device without field plate structure to over 900 V without any area overhead penalty.     

Polaron jump conductivity in films of vitreous oxide semiconductors in an intense DC magnetic field

Experimental data on the field dependence of static conductivity of vitreous oxide semiconductors (VOS) based on V₂O₅ are analyzed. To describe the effects of an intense electric field a model is proposed which assumes localization of small radius polarons (SRP) by the Coulomb field of positively charged defect centers (the bound SRP model). Within the framework of this model an expression is obtained which defines the flux density of charge carriers (J) in an electric field of arbitrary intensity (F), which in the limit of an intense electric field leads to a linear dependence of ln J on F^1/2. With the parameters found for the model the calculated function J(F) agrees well with experimental dependences of current upon F for VOS films in the vanadium-borate system. The most probable nature of defect centers in the given materials is anion (oxygen) vacancies. The results obtained agree with a previous analysis of field dependence of low-frequency dielectric permittivity also based on the bound SRP model.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 95–100, December, 1988.     

Probability of electron emission in photoemission from doped semiconductor

Electron motion is investigated in a strong-field region —in the region of bending of the band close to the surface of a semiconductor. In this region there is a change in the electron distribution function under the action of the electric field and interaction mechanisms leading to energy loss of the hot electrons. The main characteristics of the external photoeffect are determined by the energy lost by the electron in the region of band bending and the size of the barrier at the semiconductor-vacuum interface. The electron-emission probability from a crystal containing a space-charge region is determined from the solution of the Boltzmann kinetic equation. The energy dependence of the energy scattering length of the hot electrons is taken into account in the calculation. The calculation is made for photoemission from GaAs in conditions when the interaction with polar optical phonons is the most effective energy-scattering mechanism. An expression is obtained for the energy distribution function of the emitted electrons for the case of strong electric fields. The position of the distribution-function maximum depends on the electric field and the effective interaction constant with phonons. The current and quantum yield of the photoeffect are calculated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 81–87, October, 1978.In conclusion, it remains to extend profound thanks to V. L. Bonch-Bruevich for Ms constant interest in the work.     

Radiation of an electron in an electric field

By the methods of classical theory, the motion of an electron in the field of a longitudinal electric wave is analyzed. This field may be taken as a model of the accelerating field at the axis of a linear accelerator. It was shown that the radiation of electrons in this field is analogous to the radiation in a constant homogeneous electric field.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 96–99, May, 1976.The authors are sincerely grateful to Prof. V. A. Bagrov for formulating the problem and for his constant interest in the work.     

Probability distribution of the breakdown electric fields of polymer dielectrics

The probability distribution is derived for the breakdown electric field of polymers, treated as inhomogeneous dielectrics. The extremal distribution and the Weibull distribution are shown to be particular cases of the result found. The experimental results found with low-pressure polyethylene and polyethylene, Styroflex, and polyethylene terephthalate films are consistent with the theoretical probability distribution found for the breakdown electric field.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 49–55, January, 1971.     

Non-linear equations of state of second-order electromechanical effects

It follows from thermodynamic considerations that the observed influence of the electric field on the elastic coefficients is connected with certain — from the viewpoint of the piezoelectric equations of state — non-linear electromechanical effects observed before. Effects which are in a similar relation as the direct and the reversed piezo-electric effect can also be found among them. The relations between constants describing the individual effects enable us to compare the experimental results obtained by different methods. Thus they verify our own measurements.In the first approximation all the non-linear electromechanical effects were included in the piezo-electric equations of state which were thus written in a non-linear form.I am greatly indebted to Dr. J. Tichý and V. Janovec, CSc, for a number of valuable comments which helped to improve my paper.     

Stimulated and spontaneous far infra-red emission from uniaxially strained gapless Hg<Subscript>1−x</Subscript>Cd<Subscript>x</Subscript>Te

The intensive far infra-red irradiation in the range of 80–100 μm was observed in uniaxially strained gapless p-Hg_1−xCd_xTe (MCT) with x = 0.14 in the strong electric field. The inverse occupation in strained MCT is created because the hot electrons distribution occurs in the c-band under impact ionization, while the holes are localized near the v-band top. The probability of band-to-band radiative transition increases dramatically when the acceptor level becomes resonance in the v-band. At threshold values of strain and electric field (P = 2.5–2.7 kbar, E = 50–55 V/cm), increase in irradiation (by 3 orders of magnitude) and increase in current (by 4–6 times) occur.     

Particle with anomalous moments in an axial magnetic field

The exact solutions of the generalized phenomenological Dirac equation in an axisymmetrical time-invariant magnetic field are discussed. The influence of an anomalous magnetic and a postulated electric moment on the spectrum of fermions moving in that field is investigated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 36–39, May, 1981.The author is grateful to Prof. V. G. Bagrov for interest and useful consultations.     

Transition probabilities of neon atom in a constant electric field

The probability of 5s-3d, 5s-3p, 5p-3s, 5d-3s, 4d-3p, and 4f-3p transitions of Ne I in an electric field is calculated. It is shown that the probability of the permitted transitions 5s-3p and 5p-3s is unchanged with increase in the field from 0 to 50 kV/cm, while the probability of the forbidden transitions 5s-3d and 5d-3s is very small. In the given range of field strengths, the probability of permitted 4d-3p transitions markedly falls and intense forbidden 4f-3p transitions appear. Of the configurations considered, the electric field has most effect on those with2.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 67–70, March, 1979.     

Production of electron-positron pairs on nuclei in the field of a bichromatic plane electromagnetic wave

The exact solution of the Dirac equation for an electron in the field of a bichromatic plane electromagnetic wave — with components that are monochromatic waves propagating in one direction — is used to calculate the probability of e⁺e^– pair production on a nucleus in the field of such a wave. This influence of the nucleus is treated perturbatively as an external Coulomb field. The cases of small and large values of the intensity parameters of the wave components are considered and the passage to the limit of a crossed field is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 33–40, September, 1978.We are very grateful to V. R. Khalilov for a fruitful discussion of the results.     

The influence of the drift shift of electrons undergoing thermalization on the kinetic characteristics of geminate conductivity and recombination

A program for numerically solving the Smoluchowski equation with a modified initial condition taking into account the drift shift of electrons that experience thermalization in an external electric field was developed. The probability of survival and the polarization current of isolated ion pairs were calculated. Shift effects were shown to be especially strong in the region of medium electric fields on the order of 10⁷ V/m and noticeably weaker in both low and high fields. This was related to the proportional relation between the drift shift and electric field applied. The program was used to critically analyze the available experimental data on pulsed photoconductivity of polyacenes.     

Attenuation of the Electric Potential and Field in Disordered Systems

We study the electric potential and field produced by disordered distributions of charge to see why clumps of charge do not produce large potentials or fields. The question is answered by evaluating the probability distribution of the electric potential and field in a totally disordered system that is overall electroneutral. An infinite system of point charges is called totally disordered if the locations of the points and the values of the charges are random. It is called electroneutral if the mean charge is zero. In one dimension, we show that the electric field is always small, of the order of the field of a single charge, and the spatial variations in potential are what can be produced by a single charge. In two and three dimensions, the electric field in similarly disordered electroneutral systems is usually small, with small variations. Interestingly, in two and three dimensional systems, the electric potential is usually very large, even though the electric field is not: large amounts of energy are needed to put together a typical disordered configuration of charges in two and three dimensions, but not in one dimension. If the system is locally electroneutral—as well as globally electroneutral—the potential is usually small in all dimensions. The properties considered here arise from the superposition of electric fields of quasi-static distributions of charge, as in non-metallic solids or ionic solutions. These properties are found in distributions of charge far from equilibrium.