In this paper a low-energy-electron diffraction (LEED) theory for molecular crystals is presented. The possibility of creating Frenkel excitons by the incident low-energy electrons is considered. The evaluation of the terms of the differential scattering cross section series is based on a set of...

This paper deals with two equations for classical stochastic diffusion in a potential. First, the full Fokker-Planck equation in phase-space for a Brownian particle in a periodic potential and linearly coupled to an external field is considered. The solution discussed previously by the author...

In a previous work we report a comparative study of the molecular motions in gaseous and liquid methane and argon. In the present work we present the results of a study of the molecular motions in liquid ethane at three widely different temperatures. The aim is to study the...

A new formula for the binary collision expansion of the unitary operator U (t2, t1) is proposed. The formula is applied to the expansion of the partial Green's functions of Kadanoff-Baym in powers of the correct binary scattering amplitude. It is shown that certain linked diagrams of...

The ground state energy, the excitation spectra and the structure factors of weakly coupled mixtures of charged particles (bosons or fermions) are obtained in the well-known framework of the Feynman diagrams. The general theory, which is developed in a first part, is then applied to the three...

Under the influence of second-order gradients in the temperature, an anisotropy in the rotational angular momenta in a gas can be set up, giving rise to a birefringence. Preliminary measurements on this effect, called heat-flow birefringence, are reported. An interpretation of the results is...

Classical systems with mixed canonical and dissipative dynamics are studied in terms of generalized Langevin equations for fluctuating variables. This class of systems embraces all models studied in recent papers on critical dynamics. The probability distributions satisfying the associated...

For a dilute and nondegenerate relativistic spin-12 system two kinds of Wigner functions are defined: one has sixteen spinor components and the other four spin components. Their relationship is established. Statistical expressions for the current density, the energy-momentum density and the spin...

In a previous paper, the partition function of the 16-vertex model was shown to be invariant under a group of linear transformations in the space of the vertex weights. According to a theorem by Hilbert, every algebraic invariant such as the partition function for a finite lattice can be...

In this paper a low-energy-electron diffraction theory for molecular crystals is presented. The possibility of creating Frenkel excitons by the incident low-energy electrons is taken into account. The evaluation of the terms of the differential scattering cross section is based on a set of...