It is shown that the ordinary semiclassical theory of the absorption of light by exciton states is not completely satisfactory (in contrast to the case of absorption due to interband transitions). A more complete theory is developed. It is shown that excitons are approximate bosons, and, in interaction with the electromagnetic field, the exciton field plays the role of the classical polarization field. The eigenstates of the system of crystal and radiation field are mixtures of photons and excitons. The ordinary one-quantum optical lifetime of an excitation is infinite. Absorption occurs only when "three-body" processes are introduced. The theory includes "local field" effects, leading to the Lorentz local field correction when it is applicable. A Smakula equation for the oscillator strength in terms of the integrated absorption constant is derived.

a Quantum-Mechanical Theory of the Contribution of Excitons to the Complex Dielectric Constant of Crystals.

Complex (dusty) plasmas: current status, open issues, perspectives

Complex (dusty) plasmas are composed of a weakly ionized gas and charged microparticles and represent the plasma state of soft matter. Complex plasmas have several remarkable features: Dynamical time scales associated with microparticles are ``stretched'' to tens of milliseconds, yet the microparticles themselves can be easily visualized individually. Furthermore, since the background gas is dilute, the particle dynamics in strongly coupled complex plasmas is virtually undamped, which provides a direct analogy to regular liquids and solids in terms of the atomistic dynamics. Finally, complex plasmas can be easily manipulated in different ways---also at the level of individual particles. Altogether, this gives us a unique opportunity to go beyond the limits of continuous media and study---at the kinetic level---various generic processes occurring in liquids or solids, in regimes ranging from the onset of cooperative phenomena to large strongly coupled systems. In the first part of the review some of the basic and new physics are highlighted which complex plasmas enable us to study, and in the second (major) part strong coupling phenomena in an interdisciplinary context are examined. The connections with complex fluids are emphasized and a number of generic liquid and solid-state issues are addressed. In summary, application oriented research is discussed.

Complex plasmas: An interdisciplinary research field

Hydromagnetic surface waves, excited either by a MHD plasma instability or by an externally applied impulse, are shown to resonantly mode convert to the kinetic Alfven wave, the Alfven wave having a wavelength comparable to the ion gyroradius in the direction perpendicular to the magnetic field. The kinetic Alfven wave has a component of its electric field in the direction of the ambient magnetic field and can accelerate plasma particles along the field line. Because of the property of the wave the acceleration occurs on a thin magnetic surface separated by the ion gyroradius. A possible relation between this type of acceleration and the formation of aurora arcs is discussed.

Particle acceleration by MHD surface wave and formation of aurora

An externally applied oscillating magnetic field (at a frequency near 1 MHz for typical tokamak parameters) resonantly mode converts to the kinetic Alfven wave, the Alfven wave with the perpendicular wavelength comparable to the ion gyroradius. The kinetic Alfven wave, while it propagates into the higher density side of the plasma after the mode conversion, dissipates due to both linear and nonlinear processes and heats the plasma. If a magnetic field of 50 G effective amplitude is applied, approximately 10 MJ per cubic meter of energy can be deposited in 1 sec into the plasma. The heating rate here is faster than that in the transit time magnetic pumping by a factor of β−1.

/pdf/kinetic-processes-in-plasma-heating-by-resonant-mode-42szfq4dyz.pdf

Kinetic processes in plasma heating by resonant mode conversion of Alfvén wave

Principles of plasma electrodynamics

The first € price and the £ and $ price are net prices, subject to local VAT. Prices indicated with * include VAT for books; the €(D) includes 7% for Germany, the €(A) includes 10% for Austria. Prices indicated with ** include VAT for electronic products; 19% for Germany, 20% for Austria. All prices exclusive of carriage charges. Prices and other details are subject to change without notice. All errors and omissions excepted. A.F. Alexandrov, L.S. Bogdankevich, A.A. Rukhadze Principles of Plasma Electrodynamics

CONTENTS 1. Introduction 163 2. Formulation of problem and initial equations 164 3. Limiting currents in uncompensated electron beams 165 4. Critical currents in compensated unbounded electron beams 168 5. Influence of finite longitudinal dimensions of the system on the critical currents in electron beams 170 6. Interaction of unbounded relativistic electron beams with a plasma 172 7. Stability of bounded electron beams in a plasma 174 8. Critical currents of relativistic electron beams in a plasma 175 9. Comparison of theory with experiment 176 Cited literature 178

https://iopscience.iop.org/article/10.1070/PU1971v014n02ABEH004456/pdf

Stability of relativistic electron beams in a Plasma and the problem of critical currents

The results of theoretical analysis of the oscillation spectrum of a plasma placed in a very strong quantizing magnetic field are presented. It is shown that in ultra-quantum limit, when all particles occupy the first Landau level, in an inhomogeneous quantized two-component plasma, volume quantum drift waves arise. These waves become unstable under some circumstances.

Quantum drift waves

http://iopscience.iop.org/article/10.1070/PU1961v004n03ABEH003357/pdf

Anri A. Rukhadze

Papers

Principles of plasma electrodynamics

Principles of plasma electrodynamics

Stability of relativistic electron beams in a Plasma and the problem of critical currents

Quantum drift waves

Electrodynamics of media with spatial dispersion