Radiation emission associated with switching in crystalline Boron

Infrared radiation associated with switching in Boron single crystal has been detected and analyzed. Time correlation between switching and radiation events, spectral distribution of the radiation as well as its intensity as a function of current and temperature are reported. All the observed features suggest that recombination processes are the origin of this phenomenon and give information on the postswitching conduction mechanism of Boron.     

Phase jump in resonance harmonic emission driven by strong laser fields

We present a theoretical investigation of the multiphoton resonance dynamics in the high-order-harmonic generation(HHG) process driven by a strong driving continuous wave(CW) field along with a weak control harmonic field.The Floquet theorem is employed to provide a nonperturbative and exact treatment of the interaction between a quantum system and the combined laser field.Multiple multiphoton-transition paths for the harmonic emission are coherently summed.The phase information about paths can be extracted via the Fourier transform analysis of the harmonic signals which oscillate as a function of the relative phase between driving and control fields.Phase jumps are observed when sweeping across the resonance by varying the frequency or intensity of the driving field.The phase variation as a function of driving frequency at a fixed intensity and as a function of the intensity at a fixed driving frequency allows us to determine the intensity dependence of the transition energy of quantum systems.     

Defect formation kinetics in alkali halides in very strong electric fields

Experimental investigations of defect formation in alkali halide crystals have been carried out over a broad range of electric fields from 10⁴ to 10⁷ V/cm with different field pulse widths. It is shown that not only the electric field strength but the length of time it is applied is important. The effect of defect formation processes on the shapes of the current-voltage and voltage-brightness characteristics of the samples was studied in the indicated field range. The defect formation mechanism in alkali halide crystals in very strong electric fields has been better defined. Tomsk State University Academy of Control Systems and Radio Electronics. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 3–6, April, 1997.     

超强频率梳激光场驱动下多光子共振谐波辐射的相位突变研究

本文从理论上研究了在双色频率梳激光场驱动下多光子谐波辐射光谱中的相位突变现象。我们利用Floquet理论非微扰地模拟了频率梳激光场与原子分子等量子系统的相互作用过程。谐波辐射信号是多光子偶极跃迁相干叠加的结果,通过调节频率梳激光场间的相对相位,可以相干地控制谐波辐射信号的强度。通过对谐波信号进行傅里叶变换,可以提取不同跃迁路径的相对相位信息。我们通过改变频率梳组激光场的强度和频率组分实现多光子跃迁频率,让其跨越共振跃迁频率时,谐波相位会发生突变。从而可以观测超强激光场驱动下量子系统共振跃迁频率的斯塔克能移。     

Hysteresis of conduction via impurities in uncompensated crystalline silicon in strong crossed electric and magnetic fields

It was observed that in uncompensated silicon in sufficiently strong crossed electric (E) and magnetic (H) fields the conductivity σ exhibits hysteresis as a function of E with H=const and as a function of H with Econst. For the same values of E and H the conductivity can differ by a factor of 10⁵. Weak pulses of a field E transfer the conductivity from one branch of the hysteresis loop to another. Very low-intensity background radiation radically changes the form of this loop. The results can be attributed to an insulator-metal transition stimulated in the D ⁻ band of silicon by a strong electric field. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 1, 70–74 (10 January 1999)     

Macroscopic calculation of air shower radio emission

Two patterns of calculation of radio emission from extensive air showers (EAS), the so-called microapproach and macroapproach, are considered. The predictions of these approaches are compared by calculating the spatial distribution of the 40 MHz radio emission at the EAS energy 10¹⁶ eV.     

Two-electron atoms in strong fields

Multiphoton excitation and ionization of two-electron atoms under strong laser pulses, with emphasis on double excitation, is reviewed. After an introduction to the basic concepts of traditional single-photon spectroscopy and methodology, the main phenomena and experimental observations under multiphoton excitation in the perturbative regime are summarized. That is followed by the discussion of the main ideas underlying various non-perturbative approaches, especially as they pertain to the two-electron problem. The present state of understanding non-perturbative time-dependent behavior, in that context and in relation to issues such as correlation, double excitation, sequential and direct double ionization, is then formulated and discussed. The article ends with a summary of effects relating to autoionizing states in strong fields and an outlook for future developments.     

Simulation of electromagnetic shower formation in a Germanium crystal

Abstract

When high-energy electrons penetrate crystalline matter, the successive processes of photon emission and pair production form an electromagnetic shower. If the incident electrons are directed along the crystal axis, the cross section for photon emission is drastically enhanced because electrons in ‘channeling’ states feel a strong electric field continuously. Experiments designed to detect this effect were performed at CERN. The results showed an anomalous peak in the energy loss spectrum of the emerging electrons. In this paper, we report results of a Monte-Carlo simulation of shower formation in a Germanium crystal. Our results agree with the experimental data more quantitatively than previous simulations. We simulated a shower formation by incident photons as well.     

Positronium and Muonium in strong magnetic fields

The relativistic two-body problem in a constant magnetic field B of arbitrary strenght is elaborated. A new spin operator quadratic in B is derived and a change of sign in a relativistic Zeeman correction is pointed out.     

Dipole relaxation in weak and strong fields

The process of dipole relaxation in a homogeneous dielectric is studied on the basis of a two-state dipole model. The external field is not assumed to be weak. Two types of applied electric fields are considered: a linearly increasing field, and a field which changes by steps. At the present time pulsed electric fields have found wide application in electron-ion technology.Translated from Izvestiya VUZ. Fizika, No. 1, pp. 95–100, January, 1972.     

Grantmakher-Kaner effect in strong magnetic fields

Gantmakher-Kaner (GK) effect in a compensated metal is studied theoretically. The dependence of the amplitude of GK oscillations from the polarization of exciting radio-frequency field is found. Effect results from the excitation of doppleron in the plate. In polarization, in which the doppleron exists, the part of skin-layer field energy, contained in harmonics with the length close to cyclotron displacement of resonant carriers, is carried into the slab by doppleron. This results in decreasing of GK oscillations in this polarization in comparison with an opposite one.     

Exciton condensation in strong magnetic fields

The density correction to the chemical potential of excitons in a strong magnetic field was calculated. The possibilities of Bose-Einstein condensation of excitons and their condensation into electron-hole liquid (EHL) were studied. Magnetic field ranges in which these processes can be observed were determined.     

Quantum dynamics in strong fluctuating fields

A large number of multifaceted quantum transport processes in molecular systems and physical nanosystems, such as e.g. nonadiabatic electron transfer in proteins, can be treated in terms of quantum relaxation processes which couple to one or several fluctuating environments. A thermal equilibrium environment can conveniently be modelled by a thermal bath of harmonic oscillators. An archetype situation provides a two-state dissipative quantum dynamics, commonly known under the label of a spin-boson dynamics. An interesting and nontrivial physical situation emerges, however, when the quantum dynamics evolves far away from thermal equilibrium. This occurs, for example, when a charge transferring medium possesses nonequilibrium degrees of freedom, or when a strong time-dependent control field is applied externally. Accordingly, certain parameters of underlying quantum subsystem acquire stochastic character. This may occur, for example, for the tunnelling coupling between the donor and acceptor states of the transferring electron, or for the corresponding energy difference between electronic states which assume via the coupling to the fluctuating environment an explicit stochastic or deterministic time-dependence. Here, we review the general theoretical framework which is based on the method of projector operators, yielding the quantum master equations for systems that are exposed to strong external fields. This allows one to investigate on a common basis, the influence of nonequilibrium fluctuations and periodic electrical fields on those already mentioned dynamics and related quantum transport processes. Most importantly, such strong fluctuating fields induce a whole variety of nonlinear and nonequilibrium phenomena. A characteristic feature of such dynamics is the absence of thermal (quantum) detailed balance.

Quantum dynamics in strong fluctuating fields

All authors

Igor Goychuk &; Peter Hänggi

https://doi.org/10.1080/00018730500429701

Published online:

19 February 2007

Table     

Coulomb collisions in strong magnetic fields

Summary Scattering cross-sections, reflection and transmission coefficients are derived for charged-particle potential scattering in the presence of a quantizing constant magnetic field within the Green's function approach. The optical theorem and the limit of the cross-section for vanishing values of the magnetic field have also been obtained. A numerical analysis of the total cross-section for different magnetic-field intensities and values of the screening constant has been performed. The total cross-sections are found to differ significantly from the field-free ones only for magnetic-field intensities and incident particle energies such that only few Landau channels are open. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Radiative process in strong magnetic fields

Abstract

The behavior of electromagnetic processes in strong magnetic fields is currently of great interest in high-energy astrophysics. Observations of neutron stars indicate that magnetic fields larger than 10¹² Gauss exist in nature. In fields this strong, where electrons behave much as if they were in bound atomic states, familiar processes undergo profound changes and exotic processes become important. Strong magnetic fields affect the physics in several fundamental ways: energies prependicular to the field are quantized, transverse momentum is not conserved and electron/positron spin is important. The relaxation of transverse mometum conservation allows first order processes and their inverses: one-photon pair production and annihilation, synchrotron/cyclotron radiation and absorption, which are kinematically forbidden under field-free conditions. The first two are essentially quantum-mechanical and hence significant only in fields whose strength approaches the critical field, B _cr = 4.414 × 10¹³ Gauss. One-photon pair production is likely to be the dominant source of e ⁺ -e ^? pairs in fields exceeding 10¹² Gauss. While synchrotron radiation and absorption are observable as classical electromagnetic processes in weak fields, they are considerably different in high fields, where the classical synchrotron radiation formulae can violate conservation of energy, and predict too large an emissivity and electron energy loss rate. The second-order processes: two-photon pair production and annihilation and Compton Scattering, are also modified in strong fields. The discreteness of e ⁺ - e^? pair states causes resonant behavior in the cross sections and decreases the second-order rates from their free-space values. These processes play an important role in modelling high energy emission from pulsars and gamma-ray bursts.