Ionization and excitation of some atomic targets and metal oxides by electron impact

We have calculated total inelastic and total ionization cross-sections for collisions of electrons on atomic targets oxygen (O), aluminium (Al) and copper (Cu) and metal oxides AlO and Al₂O, at impact energies from near excitation threshold to 2000 eV. A complex (optical) energy-dependent interaction potential is used to derive total inelastic cross-sections resulting from ionization as well as excitation processes. The inelastic cross-sections are bifurcated into discrete and continuum contributions and total ionization cross-sections have been deduced therefrom. Our calculation also provides information, hitherto sparse, on the excitation processes in the atomic targets O, Al, Cu and metal oxides AlO, Al₂O. Adequate comparisons are made with other theoretical and experimental data.     

The theory of the optogalvanic effect in metal vapour-rare gas discharges

A theory of the laser-excited optogalvanic effect in metal vapour-rare gas discharges is elaborated. The metal vapour depletion due to the ionization processes and the energy losses from the plasma caused by the ion and electron flux to the wall and the elastic and inelastic collisions between electrons and atoms are taken into account. The metal atom depletion increases if the discharge current or the intensity of the laser radiation are increased. The more complete energy balance leads to a substantially greater optogalvanic signal than obtained from previous theories. The metal atom depletion, however, appreciably decreases the optogalvanic signal except very small discharge currents.     

Striations als Eigenlösungen der Elektronenbewegung im elektrischen Feld

A simple model for the motion of electrons in an inhomogeneous electric field is derived. With this model the striations in a weakly ionized low pressure discharge can be explained as a phenomenon of the energy relaxation. In a periodical electric field resonances occur, for which the voltage across one striation equals the average energy gain of an electron between two inelastic collisions, divided by an integer. These resonances are recognized as eigensolutions in the homogeneous field. The influence of the elastic and ineiastic collisions on the damping of the striations is discussed. In a first approximation the energy loss at the elastic collisions can be taken into account by a frictional contribution to the voltage across one striation. This voltage and the energy distribution function in moving striations are calculated and compared with measurements of other authors.     

Low-pressure RF discharge in the free-flight regime

The self-consistent equations system for low-pressure RF discharge in the free-flight regime is formulated. The expressions for the electron energy diffusion coefficient due to electron-neutral collisions and to the electron collisions with the plasma-space charge moving boundary (stochastic heating) are derived. If the electron-neutral elastic collisions frequency exceeds the inelastic one, the conventional two-term approximation for the electron distribution function (EDF) can be generalized, and the space-time-averaged electron kinetic equation can be reduced to the one-dimensional energy diffusion one. The fast electrons attached to the electrode surface can also be accounted for in this equation. It is shown that in the cases of (a) spatially uniform ion profile, (b) for frequencies that are small compared with the electron bounce frequency, and (c) for frequencies exceeding the electron plasma one in the sheath, the stochastic heating vanishes     

The Franck-Hertz Experiments, 1911–1914 Experimentalists in Search of a Theory

In 1911, James Franck and Gustav Hertz began a collaboration to investigate the nature of collisions of slow electrons with gas molecules that led to a series of carefully planned and executed experiments, culminating in their discovery of inelastic collisions of electrons with mercury vapor atoms in 1914. This paper tells the story of their collaboration and the eventual reinterpretation of their results as a confirmation of Niels Bohr’s new atomic theory, largely as a result of experiments done in North America during the Great War.     

Untersuchung der Prozesse in der aktiven Zone der Hohlkatodenbogenentladung I. Die Energieverteilungsfunktion der Elektronen,die Anregungs- und Ionisationsgeschwindigkeit

In this paper the processes of excitation and ionization inside the cathode of a hollow cathode are discharge will be studied. The electron energy distribution function is calculated from the kinetic equation. For this we take into account the following processes: elastic and inelastic collisions of electrons with atoms, Coulomb interaction between emitted fast electrons and electrons of the plasma.     

Solution of the Boltzmann equation for electrons in the discharges in metal vapour-helium mixtures

The Boltzmann equation was applied to the electron gas in the positive column in a helium-metal vapour mixture discharge. The problem was solved both numerically and approximately taking into account elastic and inelastic collisions of electrons with helium and metal atoms as well as mutual impacts of electrons. Separately the influence of Zn, Cd and Hg atoms on the mean kinetic energy, the mobility (drift velocity) and the diffusion of the electrons was investigated. Approximative relations for those quantities were found and a physical interpretation of their behaviour is given.     

Dissociative excitation of even triplet and quintet levels of the iron atom in collisions of electrons with iron diiodide molecules

The method of extended crossing beams is used to study inelastic collisions of slow electrons with iron dichloride molecules. The dissociative excitation of even triplet and quintet levels of the iron atom at the incident electron energy of 100 eV is examined. The resulting dissociative excitation cross sections are compared to the cross sections of the excitation of FeI in electron-atom collisions.     

Correlation effects in electron-ion collisions in a strong laser field

We examine elastic and inelastic scattering of electrons by ions in intense laser light. A method of numerical investigation of the scattering characteristics based on regularizing the Coulomb singularity is proposed. We show that over a broad range of parameter values the transport scattering cross section is weakly dependent on the intensity of the high-frequency field. We detect a significant modification of the dependence of the effective inelastic scattering cross section. We also show that the energy exchange with the field is determined by a fairly small group of electrons, called the representative electrons. Finally, we propose a qualitative model that explains our results by the fact that the leading contribution is provided by inelastic collisions of electrons with relatively small impact parameters traversing the region important for the interaction at large angles. Zh. éksp. Teor. Fiz. 115, 463–478 (February 1999)     

Electron distribution function in a weakly ionized He-Hg mixture

The electron energy distribution functions for He-Hg mixture in a uniform electric field are calculated for differentE/N and relative mercury concentration? from fundamental cross-section data. The Boltzmann equation is applied considering the elastic and inelastic collisions of electrons with neutrals of the both components. From these distributions and elastic collision cross-section (for He and Hg) drift velocity, diffusion coefficient and mean electron energy are computed. The electron energy losses in elastic and inelastic collisions over the considered region of the parameters are discussed.     

Spin dependent mean-free path of low-energy electrons in ferromagnetic materials

Spin resolved attenuation measurements of electrons transmitted through overlayers of Fe and Co show that the electron inelastic mean free path (IMFP) in these materials is spin-dependent at low energies. The spin-up IMFP is larger than the spin-down IMFP. The values from different studies are in reasonable agreement. The data suggest that the origin of the spin dependence is mainly due to inelastic processes. Effects from spin dependent elastic scattering have not been identified directly in these experiments. The spin filter effect based on preferential attenuation of spin-down electrons can be used as a basis of spin polarization detectors.     

On the dynamics of electrons in an impure metal

The inelastic scattering of the electrons of an impure metal by a screened Coulomb interaction is investigated. It is found that the rate of such an inelastic scattering is increased which can be explained by a loss of momentum conservation which in turn results from loss of translational symmetry introduced by the defects of an impure metal. Eventually, a linearised Boltzmann equation is derived for time and space dependent perturbances of the electronic distribution function. The collision integral takes into account impurity scattering as well as electron-electron and electron-phonon scattering. In an impure metal the terms corresponding to the last two processes are modified as discussed above and in a previous paper on the electron-phonon interaction.     

Problems of Deep Inelastic Lepton-Nucleus Interaction

The deep inelastic scattering of electrons (muons) and neutrinos on the nuclei and the process of lepton pair production in hadron-nucleus collisions are considered. The expressions for the corresponding differential cross-sections are derived provided the final lepton and the spectator fragment of the initial nucleus are detected in coincidence. The structure functions of the processes under consideration are analysed by the principle of automodelity. Some scale-invariant regularities are established for them. In the framework of “light front” formalism for many-body systems the relations of these structure functions to the usual structure functions of the deep inelastic lepton hadron interaction are obtained. A hypothesis is put forward on the scale invariance of structure functions with respect to the ξ-variable which is some complicated dimensionless combination of kinematic invariants.     

New mechanism of atomic particle ionization in crystals

It is shown that at channeling in a crystal the electron loss by a fast ion due to “inelastic” collisions with the target electrons may be of importance as the “elastic” electron loss which is dominating in an amorphous target can be strongly reduced in a crystalline one.     

Luminescence from exciton polaritons in weakly excited GaAs based on exciton-electron collisions

Luminescence spectra from exciton polaritons in GaAs have been investigated. The calculations are based on exciton-electron inelastic collisions and the Pauli principle for scattered electrons. The observed spectra were compared with the theoretical ones.     

Implementation of an inelastic collision operator into KIPP‐SOLPS coupling and its effects on electron parallel transport in the scrape‐off layer plasmas

This paper develops an inelastic collision operator for the Kinetic Code for Plasma Periphery (KIPP) code to investigate the kinetic effects of electron cooling due to inelastic collisions. It is fully tested based on the self‐consistent KIPP‐SOLPS coupling algorithm by being compared to the ADAS database. The collisional radiative rate coefficients from the ADAS database for deuterium atomic physics can be recovered using the inelastic collision operator with assuming Maxwellian electrons, which shows that the inelastic collision operator works well for various plasma conditions. Across a wide range of plasma conditions in the scrape‐off layer, KIPP‐SOLPS coupling simulation results with the implementation of an inelastic collision operator are not significantly different from results using a simpler uniform cooling scheme. The uniform scheme is thus recommended rather than including computationally intensive inelastic collision physics.     

Polarization detection of trapped electrons via interaction with polarized atoms

Electrons were trapped in an electrostatic quadrupole trap with superimposed homogeneous magnetic field. The electrons were polarized by spin exchange with a polarized atomic beam. The free trapped electron polarization was converted to a change in the electron translational energy via spin-dependent inelastic collisions with the atomic beam, and the electron translational temperature was monitored. Discussed are the development of this variation of the measurement technique, characteristics of electron storage, and the electron-polarized atom inelastic interaction as a function of electron temperature and time. The method has been applied to the detection of the (g-2) resonance of free, stored electrons.     

Electron scattering off simple atoms for large momentum transfer collisions

In a previous paper this author examined the Born expansion and isolated those parts of the expansion that contribute most significantly to the scattering amplitude for large momentum transfer collisions in inelastic collisions from the ground state of both hydrogen and helium. It turned out that certain terms where the scattering electron interacts once with the nucleus and once with the other electron dominate. The physical reason is that large momentum transfer collisions require the nucleus to take the bulk of the incident momentum but require an interaction with the one of the bound electrons to change the state of the atom. The arguments are quite general and this paper will extend this analysis by comparing the inelastic results obtained by this method for hydrogen and helium to a close coupling calculation with many intermediate states. Further, we will extend this analysis to the correction to the 1st Born result for elastic electron-hydrogen and electron-helium collisions and provide some results for scattering from the initial metastable states of hydrogen for large momentum transfer collisions. A comparison of the results of this analytic approach will be made to the numerical close coupling approach and experiments where available. The agreement is remarkable.     

分子束穿透托卡马克等离子体的机理

由于分子束分子密度远高于周围等离子体密度,沿托卡马克内的磁力线进入分子束区域的电子因非弹性碰撞而失去部分能量和动量,引起分子束区的电子堆积,形成静电双层,其屏蔽效应是分子束可以较深透入托卡马克等离子体的主要机制。     

Relativistic kinetic theory of quantum systems: IV. Transport equation for the neutrino component of an eeνeνe-mixture

The transport equation for a neutrino system derived previously is extended to include binary collisions involving electrons, positrons and antineutrinos. The transition amplitudes for these collision processes are specified in terms of an effective Hamiltonian density following from the Weinberg-Salam theory. The resulting equation incorporates the reactive processes e$\text{e}$ ? ν$\text{ν}$ and exhibits the electron and positron spins explicitly. It is shown to be form invariant under Lorentz transformations.