Density-matrix approach to dynamics of multilevel atoms in laser fields

The theoretical foundations of atom dynamics in laser fields are reviewed in relation with applications to laser spectroscopy, control of atomic motion, atom traps and frequency standards. We present an ab initio approach to the description of internal and translational dynamics of multilevel atoms in laser fields based on the equations for the atomic density matrix. Semiclassical density matrix equations are reviewed and applied to the description of properties of atomic populations and coherences for a classically moving atom. Quantum-kinetic equations for the atomic density matrix are reviewed for the multilevel interaction schemes. The procedure of reduction of the quantum-kinetic equations to the Fokker–Planck quasiclassical kinetic equation for the atomic distribution function is described. Quasiclassical kinetic equations are applied to the multilevel atomic schemes to describe the translational atomic dynamics. Basic types of the dipole radiation forces on atoms are considered for realistic cases of multilevel dipole interaction schemes. The applications of the theory of atomic dynamics in laser fields to the laser cooling, magneto-optical and optical dipole traps, and optical lattices are discussed.