The direct evaluation of attosecond chirp from a streaking measurement

We derive an analytical expression that relates the breadth of a streaked photoelectron spectrum to the group-delay dispersion of an isolated attosecond pulse. Based on this analytical expression, we introduce a simple, efficient and robust procedure to instantly extract the attosecond pulse’s chirp from the streaking measurement. We show that our method is robust against experimental artifacts.     

Excitonic susceptibility of semiconducting crystals influenced by a uniform electric field

Summary The Stahl’s polariton equations for crystals, influenced by a uniform electric field, can be solved by means of an appropriate Green’s function. The Green’s function is calculated for the half-space geometry and the field directed along the z-axis. Using its asymptotic form a formula for the excitonic susceptibility is derived.     

Action of a pulsed electron beam on Cu-Ni foils and accompanying phenomena

Influence of the action of a pulsed electron beam in the millisecond range on the composition of surface layers, structure, topography, and mechanical properties of Cu₅₀Ni₅₀ and Cu₈₀Ni₂₀ foils depending on the energy’s and pulse’s current density is studied. The formation of concentration inhomogeneities in ultrathin near-surface layers is found as well as variations in the structure, mechanical properties, and topography of the foils depending on the alloy composition and irradiation parameters.     

Dispersing of a charged drop in an electrostatic field

The characteristics of the breakup of a charged drop in a uniform electrostatic field are calculated on the basis of Onsager’s principle of minimum dissipation of energy in nonequilibrium processes. The ranges of the physical parameters where daughter droplets are emitted from two tips and from one tip of an unstable parent drop and when emission is completely absent are found. The dimensionless radii, charges, and specific charges of the daughter droplets are determined. Zh. Tekh. Fiz. 69, 26–30 (December 1999)     

Surface reconstruction of a field electron emitter

The surface and emission images of a metal field’s electron cathode in the form of a tip are simulated. The surface structure is calculated in the thin-shell and broken-bond (local-environment) models for the perfect crystal lattice. The cathode shape and macroscopic electric field are represented by the sphere-on-cone model. The amplification of a local electric field is the adjustable parameter of the model. The method of determination of the emitter tip’s crystal faces based on the analysis of the surface atoms’ environment geometry is proposed. It is shown that it is enough to restrict the consideration of geometric environment by the fifth order of the nearest neighbors for the emitter radius of 100–1000 lattice parameters (31.6–316 nm for the tungsten). The crystallographic model of work function anisotropy in the broken-bond approach is used: the local work function’s value is set in accordance with Miller indices of the face containing this area. The model adequacy is corroborated by the comparison of current-voltage characteristics and emission images with the data of the natural experiment.     

Electric fields from model lightning discharges in a neutral atmosphere

The electric fields created by lightning discharges in a neutral atmosphere are calculated in the time representation. It is shown that asymmetric strokes containing horizontal currents can generate pronounced pulsed electric fields. A high-power quasistatic field can influence the middle atmosphere together with pulses. The motion of the current wave in a complex-geometry stroke channel can lead to an increase in the number of emitted pulses. At the periphery of the lightning cell, upon the arrival of the pulse, the electric field vector turns upward, to the stroke axis, and sideward. We also expect an increase in atmospheric turbulence due to convection at the frontal part of the cloud. The emerging inhomogeneities of the atmospheric temperature and density can facilitate the onset of plasma processes generated by the electric field of a strong thunderstorm. Since convection and the focusing electric fields are concentrated at the periphery, their joint action can lead to the appearance of circular and prolate luminous formations. Institute of Radiophysics and Electronics of the National Academy of Sciences, Khar’kov, Ukraine; The University of Electro-Communications, Tokyo, Japan. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 6, pp. 699–722, June, 1998.     

Modeling the development of the stepped leader of a lightning discharge

A stochastic-deterministic model is presented for the propagation of a downward-moving leader. Lightning formation is described by a stochastic growth of branching discharge channels which is determined by the electrostatic field. The dynamics of the electric field and of the charge distribution over the lightning structure are calculated deterministically. The model includes the initiation of lightning, a preliminary discharge in a cloud, the propagation of a downwardmoving stepped leader toward the earth, and the initiation and upward motion of a return stroke from the earth’s surface. Numerical execution of the model yields a dynamic picture of the development of the downward-moving leader and of the intracloud discharge structure. The effect of the charge density in the cloud and the parameters of the developing channels on the spatial-temporal, current, and charge characteristics of the stepped leader’s propagation are studied. The effect of free-standing structures on the distribution of points on the earth’s surface where lightning strikes is examined. Zh. Tekh. Fiz. 69, 48–53 (April 1999)     

Natural line shape

The observable line shape of the spontaneous emission depends on the procedure of atom’s excitation. The spectrum of radiation emitted by a two-level atom excited from the ground state by a π pulse of the resonant pump field is calculated for the case when the Rabi frequency is much larger than the relaxation rate. It is shown that the central part of the spectral distribution has a standard Lorentzian form, whereas for detunings from the resonance that are larger than the Rabi frequency the spectral density falls off faster. The shape of the wings of the spectral line is sensitive to the form of the π pulse. The implications for the quantum Zeno effect theory and for the estimates of the duration of quantum jumps are discussed. The article is published in the original.     

Microwave radiation of the atmosphere induced by a pulsed gamma source

The model problem of the perturbation of the atmosphere by an isotropic gamma source (pulse width Δτ ≤ 100 ns) situated at various altitudes (0 ≤ h ≤ 100 km) and assumed to be a “point” source was solved. The action of emitted gamma quanta caused the formation of a spatial region in the atmosphere containing highly excited atoms and molecules, the emission from which was recorded over a certain microwave range (0.8–1.0 GHz). The amplitudes of the electric component intensity of the field of noise Rydberg radiation over the range specified were calculated. Rydberg radiation duration, type, and the degree of polarization were estimated. The shape of the emission line and the character of broadening of signals received by two receivers situated at an altitude of H ₁ = 20000 km and on the surface of the Earth (H ₁ = 0 km) were analyzed. During measurements, both receivers were situated on the axis perpendicular to the surface of the Earth.     

Standstill Electric Charge Generates Magnetostatic Field under Born-Infeld Electrodynamics

The Abelian Born-Infeld classical non-linear Electrodynamic has been used to investigate the electric and magnetostatic fields generated by a point-like electric charge at rest in an inertial frame. The results show a rich internal structure for the charge. Analytical solutions have also been found. Such fields configurations have been interpreted in terms of vacuum polarization and magnetic-like charges produced by the very high strengths of the electric field considered. Apparently non-linearity is responsible for the emergence of an anomalous magnetostatic field suggesting a possible connection to that created by a magnetic dipole composed of two magnetic charges with opposite signs. Consistently in situations where the Born-Infeld field strength parameter is free to become infinite, Maxwell’s regime takes over, the magnetic sector vanishes and the electric field assumes a Coulomb behavior with no trace of a magnetic component. The connection to other monopole solutions, like Dirac’s and ’tHooft’s Poliakov’s types are also discussed. Finally, some speculative remarks are presented in an attempt to explain such fields.     

Pion cloud and the sea of the nucleon

I review recent progress in understanding the structure of the nucleon sea and the role of the nucleon’s pion cloud. In particular, I discuss the consequences of the pion cloud for the ƌ−ū asymmetry in the proton, the neutron’s electric form factor, and the proton’s electric to magnetic form factor ratio.     

Interaction of radiation and a relativistic electron in motion in a constant magnetic field

This paper examines the effect of multiple photon emission on the quantum mechanical state of an electron emitting synchrotron radiation and on the intensity of that radiation. Calculations are done with a variant of perturbation theory based on the use of extended coherent states. A general formula is derived for the number of emitted photons, which allows taking into account their mutual interaction. A model problem is used to demonstrate the absence of the infrared catastrophe in the modified perturbation theory. Finally, the electron density matrix is calculated, and the analysis of this matrix makes it possible to conclude that the degree of the electron’s spatial localization increases with the passage of time if the electron is being accelerated. Zh. éksp. Teor. Fiz. 113, 841–864 (March 1998)     

Approximation of the Blume’s stochastic model by asymptotic models for PAC relaxation analysis

The time-dependent perturbation factors G₂(t) of PAC are numerically calculated by diagonalizing the Blume’s supermatrix when static and fluctuating electric field-gradients are simultaneously present at the nucleus. The calculated functions are fitted with the expression of G₂(t) given by isotropic models, strictly valid for asymptotic conditions. The asymptotic relations between the spin relaxation constant λ and the jump frequency w introduced in the stochastic model are found to be a good approximation in large domains of w values.     

Electric field dependence of the Curie temperature and microwave absorption in displacive ferroelectrics with impurities

The electric field dependence of the complex dielectric constant in an anharmonic defect ferroelectric crystal is calculated in its paraelectric phase from the Silverman-Joseph-Hamiltonian augmented with fourth-order phonon coordinates using double-time Green’s functions. The field and impurity dependence of the shift in the Curie temperature is discussed. An expression is obtained for the electric field dependence of dielectric loss at microwave frequencies in defect ferroelectrics. An erratum to this article is available at .     

Nonstationary radiation mode of a thin-walled piezoceramic sphere with a correcting electric circuit

A transducer in the form of a water-loaded thin-walled piezoceramic sphere is considered. On the electric side, the transducer is connected to an RL circuit. The pulsed radiation mode of the transducer is studied using the theory of equivalent schemes of piezoelectric transducers and the spectral Fourier transform. For the system under study, the parameters that provide the minimal emitted signal duration are determined for different values of the relative wall thickness of the sphere. The durations and amplitudes of acoustic pulses emitted by the transducer in the presence and absence of the electric circuit are compared.     

Dynamical beats of forward-scattered resonant synchrotron radiation as a nuclear polariton effect

The decay of the nuclear exciton (immobile collective excitation), created by a pulse of synchrotron radiation, is analyzed. It is shown that in the later phases of the decay, the exciton becomes localized at the sample’s frontal surface. Inside the sample, the secondary gamma-quanta, emitted by the contracting exciton, are converted into polaritons (mobile nuclear excitations) characterized by different frequencies and equal group velocities. On the sample’s back surface, the polariton interference causes a beating structure of the transmitted radiation, observed in experiments.     

Molecular level dynamics of genetic oscillator—The effect of protein-protein interaction

Uncovering how interactions of a set of molecular components influence the system’s dynamic behavior is important for understanding intracellular processes and elucidating design principles, but unfortunately, there are limited efforts for studying this issue. Here, we study the effect of distinct post-translational dynamics controlled by protein dimerization on oscillations in the repressilator. For this, we propose three biologically motivated model scenarios of the repressilator with monomer or dimer being the active form of repressor, and with protein-protein interactions. It is found that the dimer dissociation constant can tune oscillatory regions, frequency and amplitude. Introducing a modified linear noise approximation to evaluate fluctuations of amplitude and period in the oscillatory systems, we show that different dimerization leads to a different effect on period and amplitude in reducing noise. The manipulation of the circuit’s biochemical properties provides a practical strategy for designing a robust and tunable oscillator.     

On source radiation in an isotropic chiral medium

Radiation of external electric and magnetic sources in an isotropic chiral medium is studied by means of decomposition of the electromagnetic field into wave fields of circular polarization and introduction of the corresponding combined sources. The elementary-source fields are calculated using the Green’s function. The wave-field energy flux is discussed. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 87–90, September, 2006.     

Electromagnetic fields formed upon the interaction of ionizing radiation with matter

We propose a new approach to electromagnetic field calculations that involves the consecutive application of both quantum and classical electrodynamics methods. A current’s distribution is calculated via simulation modeling, using cross-section values obtained through quantum electrodynamics. The classical delayed potential of a current pulse of arbitrary form and duration, moving in a straight line at hyperlight velocity in the space-time representation, is calculated in an explicit form.     

Water concentration and dielectric permittivity in molecular crevices

Summary The behaviour of electric dipoles (water molecules) under the action of a high and nonuniform electric field is investigated. The model incorporates all the features of Clausius-Mossotti’s Debye’s, Onsager’s and Kirkwood’s approaches, and assumes, as a novel feature, that the dielectrophoretic drift of dipoles is balanced by dipole diffusion. A new relationship among local permittivity, electric field and water density is found that could explain why water molecules are rejected by charged molecular crevices which can engineer the binding of ionized ligands at very high rates as compared to bulk water. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.