Quantum Theory of the Electromagnetic Properties of Matter; Broadening of Spectral Lines.

R. Kh. Gainutdinov, Il'dar R. Al'Miev

V. V. Yakimets

Karim Faid

A complete stochastic theory of relaxation is developed in terms of a homogeneous equation for the averaged density matrix of a system immersed in a thermal bath.\nThis theory is then used as the basis of a new stochastic approach to the phenomenon of collisional broadening of spectral line shapes. Single photon and multiphoton processes are studied.\nThe features of a line shape are linked by simple expressions to the statistical properties of a stochastic hermitian Hamiltonian. The ordinary line shape predicted by Kubo's approach is generalized. The present approach predicts broadening as well as asymmetry and shift. A representation of line shapes in multiphoton processes by diagrams is also developed.

A. S. Kuraptsev, Igor M. Sokolov

On the basis of consequent microscopic quantum approach we calculate collective level shifts and line broadening in the polyatomic ensemble located in the Fabry-Perot cavity or near the conducting surface. We show that the cavity or the surface can essentially modify dipole-dipole interaction and consequently spectral properties of studied impurity ensembles. This modification is explained by the peculiarities of the structure of modes of electromagnetic field in these cases.

Luca Salasnich

S. Yu. Svita, Valery Alexandrovich Astapenko

The study is devoted to the theoretical analysis of ultrashort electromagnetic pulses (USP) absorption on broadened dipole transitions. Calculations are made in the frame of perturbation theory with the use of the basic formula for energy absorbed during all time of the action of USP on dipole transition. Dependences of absorbed energy upon pulse duration and carrier frequency are obtained and analyzed for different types of spectral line shape and USP parameters.