Coherent spontaneous emission from large systems

In this paper we discuss the conditions under which coherent spontaneous emission can take place in an arbitrary sample of linear dimensions smaller than a cooperation length. These conditions guarantee that the atoms—field interaction can be treated up to the second order in the Generalized Master Equation for the atoms. An equation describing coherent spontaneous emission is derived and discussed. A comparison is made between this and other known theories.     

A master equation description of open systems. III

In this paper the results of previous work on the dynamics of coupled systems are generalized. A closed equation for the reduced density operator of the relevant subsystem is derived without assumptions on the behaviour of the irrelevant one. Equations relating the expectation values of observables of the two subsystems are given. They allow to reconstruct the dynamics of one subsystem once that of the other is known.     

Effects of spatial dispersion on exciton absorption

The exciton absorption is studied in the spatially dispersive case. The energy propagation properties of the medium are used to define an appropriate absorption coefficient. The specific example of PbI₂ is considered in order to display the role of spatial dispersion.     

Fokker-Planck equation for a periodic potential

The Fokker-Planck equation in one dimension has been solved for a system in a periodic potential and linearly perturbed by a time- and space- varying external electric field. The solution is not exact, but we believe it is less approximate than any attempted previously on this problem. We have calculated the frequency and wave-vector dependent mobility and discussed its behaviour in some limiting cases.The application of our model to various physical situations is discussed.     

Analytical multiple scattering extension of the mie theory

Multiple scattering of light in aerosol is described in a simple picture within the framework of the Mie theory. Our approach leads to an analytical expression of the n-fold scattered electromagnetic field and then to a generalization of the optical parameters. The multiple scattering contributions are calculated avoiding the convergency and stability problems which are often encountered in standard numerical approaches. These problems occur due to the large number of events that have to be taken into account when large optical depths and/or a low signal to noise level exists. Such conditions are frequently encountered in atmospheric measurements.     

The Argyres-Kelley approach to the master equation and an extended theory of superradiance

A discussion of the Argyres-Kelley approach to the Master Equation is set up, and applied to the Bonifacio-Schwendimann-Haake model of Superradiance. Some properties of the approach and its limits are discussed, and an extension of the BSH theory of Superradiance is obtained.