Anomalous emission of electrons from MIM systems

In this paper the emission of electrons from thin-film systems of the structure metal-dielectric-metal (Al-Al₂O₃-Au) is studied experimentally in the voltage region below the work potential of the top electrode. The temperature and voltage dependences of the angular distribution, energy distributionsN(E) andN (Einx) and energy-angular distribution of emitted both anomalous and normal electrons were obtained.This paper is based on the RNDr thesis of the first author.     

Anomalous resonance effects in collision broadened spectral line widths

Calculations of self broadened DF vibration-rotation line widths and of widths of DF and HF broadened by each other have been performed using the Anderson theory. The calculations include effects of inexact resonances in the upper states of the fundamental band and also include dipole-dipole, dipole-quadropole and the quadropole-quadropole terms in the multipolar expansion. A qualitative discussion of the results is given.     

Positrons from supercritical fields of giant nuclear systems

During collisions of heavy nuclei with a combined chargeZ?160 the electronic 1s-state is deeply bound due to the strong Coulomb field, forZ≧173 it even enters as a resonance the lower continuum of the Dirac-Hamiltonian. In pure Rutherford scattering no qualitative indication for the filling of a dynamically createdK-hole by the spontaneous positron creation process is predicted, but the study of heavy-ion collisions with nuclear time delay due to the attractive nuclear force promises clear signatures for the decay of the vacuum. Emphasis is laid also on the quantitative influence of the electron-electron interaction and ofE0-transitions in the giant nuclear system on positron emission, the latter treated in a classical approximation. We compare our results with recent experimental data of two different groups at GSI, Darmstadt.     

Semiclassical theory of positron emission in transient supercritical atoms

Within the semiclassical approximation (WKB) we present an estimate of the cross section for spontaneous and induced positron emission during the formation of a supercritical atom in a heavy-ion collision. Energy and width of the electron levels are taken from an analytical WKB formula.     

Electrons from target and projectile ionization in simple collision systems

Summary Absolute double differential cross-sections for target ionization and projectile electron loss were determined in collisions of H⁺, H₂ ⁺,³He⁺ and³He⁺⁺ ions (0.4 to 2.0 Me V/u) with He and Ar gas targets at electron emission angles from 0° up to 60°. The experimental results are qualitatively well described by plane-wave Born approximations including screening of the projectile in target ionization and of the target atom in the case of electron loss.

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Riassunto Sono state determinate le sezioni d’urto doppie differenziali assolute per la ionizzazione del bersaglio e la perdita dell’elettrone proiettile in collisioni di ioni H⁺, H ₂ ⁺ ,³He⁺ e³He⁺⁺ (da 0.4 a 2.0 Me V/u) con bersagli di gas He e Ar ad angoli di emissione degli elettroni da 0° a 60°. I risultati sperimentali sono qualitativamente ben descritti dalle approssimazioni di Born per onde piane che comprendono la schermatura del proiettile nella ionizzazione del bersaglio e dell’atomo bersaglio nel caso di perdita dell’elettrone.

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Резюме Определяются абсолютные дважды дифференшиальные поперечные сечения для ионизации мишени и потери электровов налетающими частишами при соударениях ионов H⁺, H ₂ ⁺ ,³He⁺ и³He⁺⁺ (от 0.4 до 2.0 Me V/u) в случае газовых Не и Ar мишеней при углах эмиссии электронов от 0° до 60°. Экспериментальные результаты качественно хорощо описываются с помощью плоско-волнового борновского приближения, включая экранирование налетающей частицы при ионизации мишени в случае потери электрона.

     

Anomalous dynamics in reaction-diffusion systems

Summary We review recent developments in the study of the diffusion reaction systems of the type A+B→C in which the reactants are initially separated. We consider the case where the A and B particles are initially placed uniformly in Euclidean space atx>0 andx<0, respectively. We find that whereas ford≥2 the mean-field exponent characterizes the width of the reaction zone, fluctuations are relevant in the one-dimensional system. We also presented analytical and numerical results for the reaction rate on fractals and percolation systems. Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994.     

Anomalous magneto-oscillations in two-dimensional systems

The frequencies of Shubnikov-de Haas oscillations have long been used to measure the unequal population of spin-split two-dimensional subbands in inversion asymmetric systems. We report self-consistent numerical calculations and experimental results which indicate that these oscillations are not simply related to the zero-magnetic-field spin-subband densities.     

Anomalous Hall conductivity from the dipole mode of spin-orbit-coupled cold-atom systems

Motivated by recent experiments by Lin et al., [Nature (London) 471, 83 (2011)] that engineered spin-orbit coupling in ultracold mixtures of bosonic atoms, we study the dipole oscillation of trapped spin-orbit-coupled noncondensed Bose and Fermi gases. We find that different directions of oscillation are coupled by the spin-orbit interactions. The phase difference between oscillatory motion in orthogonal directions and the trapping frequencies of the modes are shown to be related to the anomalous Hall conductivity. Our results can be used to experimentally determine the anomalous Hall conductivity for cold-atom systems.     

Anomalous transport in disordered dynamical systems

We consider simple extended dynamical systems with quenched disorder. It is shown that these systems exhibit anomalous transport properties such as the total suppression of chaotic diffusion and anomalous drift. The relation to random walks in random environments, in particular to the Sinai model, explains also the occurrence of ageing in such dynamical systems. Anomalous transport is explained by spectral properties of corresponding propagators and by escape rates in these systems. For special cases we provide a connection to quantum mechanical tight-binding models and Anderson localization. New classes of anomalous transport behavior with clear deviations from the behavior of Sinai type are found for generalizations of these models.     

Anomalous stoner enhancements in amorphous systems

An n-orbital model describing both elastic impurity scattering and exchange interaction is examined near its instability for itinerant ferromagnetism. At the critical point and at zero temperature, long range spin fluctuations cause anomalous enhancements of the density of states near the Fermi energy with $\text{?(E) - ?(E}{}_{\mathrm{F}}\text{) ∝ |E ? E}{}_{\mathrm{F}}\text{|}{}^{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}$ in three-dimensions (3D) and with ln²|E ? E_F| in 2D. An estimation of the conductivity $\text{σ(Ω)}$ in a continuum analog model reveals Ω^{$\text{1}\text{4}$} -and ln²$\text{|Ω}{}_{\mathrm{\tau }}\text{|}$-corrections in 3D and 2D respectively.     

Anomalous susceptibility of low-dissipation bistable systems

The time-asymptotic behavior of a bistable system under conditions of a nonequilibrium phase transition of displacement type was studied. Anomalous behavior of the susceptibility of this system is observed with increase in the noise intensity. It is inferred that the effect of stochastic resonance can be observed in such systems.     

Asymmetry-induced spectral peaks in periodically forced noisy bistable systems

The occurrence of finite-width peaks in the spectral background of a time-sinusoidally forced overdamped bistable Duffing oscillator, subject to a noise-floor, is reported. The peaks, which only occur in the presence of a symmetry-breaking dc signal, are located at approximately the odd integer multiples of the forcing frequency. An analytic expression for the height of the peaks is derived and validated via computer simulations. The peak heights display a non-monotonic dependence on the system asymmetry.     

The collision of particles in granular systems

Collisions between granular particles are irreversible processes which cause dissipation of mechanical energy by fragmentation or heating of the colliders. The knowledge of these phenomena is essential for the understanding of the behaviour of complex systems of granular particles. We have developed a model for inelastic collisions of granular particles and calculated the velocity restitution coefficients, which describe all possible collisions in the system. The knowledge of these coefficients allows for event-driven many-particle simulations which cannot be performed in the frame of molecular dynamics. This approach has the advantage that very large particle numbers can be treated which are necessary for the understanding of intrinsic large-scale phenomena in granular systems.     

Sharp diffraction peaks from chaotic structures

Recently various models for spatially chaotic structures have been proposed. We study the diffraction patterns produced by plane chaotic waves incident on one-dimensional chaotic point scatterers. The spacing between the scatterers and the dynamics of the incident wave are given by a logistic map or standard map. We find a sharp diffraction peak when the incident dynamics is produced by the same map as the structure of the spatial configuration. The diffraction pattern is symmetric about the incident direction only if the map dynamics is invertible. Diffraction patterns with chaotic incident waves have a large signal-to-noise ratio and are well suited for pattern identification. We discuss possible applications to the scattering of microwaves from aperiodic structures. (c) 1997 American Institute of Physics.     

Anomalous fluctuation and relaxation in unstable systems

The essential ideas of the scaling theory of transient phenomena proposed by the author for a single macrovariable near the instability point are extended to multi-macrovariables in nonequilibrium systems. The time region is divided into three regimes according to the scaling behavior of the fluctuating parts of the macrovariables. In the first regime, the fluctuation is Gaussian and it is described by the linearized stochastic equation (or linear Fokker-Planck equation). In the second regime, the fluctuation is non-Gaussian, but it is probabilistic or stochastic (not dynamical) in the sense that the stochastic nature comes from the probability distribution in the initial regime and that each representative motion is deterministic, namely a random force can be neglected asymptotically in the second regime. In the final regime, the fluctuation is again Gaussian. A fluctuation-enhancement theorem for multi-macrovariables is given, which states that the fluctuation becomes enhanced by the order of the system size in the second regime, which is of order log , if the initial system is located just at the unstable point. An anomalous fluctuation theorem for multi-macrovariables is also proven, which states that the fluctuation is anomalously enhanced in proportion to ^–2 at times of order log if the initial system deviates by from the unstable point.This work is partially financed by the Scientific Research Fund of the Ministry of Education.