Atomic Emission Spectrum And Quantum Interference Effects In The Atom-field Coupling System

Atomic emission spectrum and phase properties of the field in some atom-field coupling systems are investigated. Effects of quantum interference between two different transition pathways on atomic emission spectrum and phase properties of the field are discussed. The effect of quantum interference among many ionization channels on photo-ionization properties of an atom in a laser-induced continuum structure system is analyzed.First the emission spectrum of an atom in a grey-body cavity is stuided. The influences of the incident field photon-number distribution, the cavity absorptivity and the system temperature on the atomic emission spectrum are discussed in detail. It is found that the influence of cavity radiation on the atomic emission spectrum could be reduced through diminishing the absorptivity of the cavity and lowering the temperature of the cavity. When the cavity field is initially in photon number state or mixed state, the emission spectrum of the two-level atom has nothing to do with the phase of the atomic dipole. If the cavity field is initially in the coherent superposition of photon number state, the emission spectrum of the two-level atom exhibits phase sensitivity. If a A -type three-level atom is initially in the coherent superposition of its two non-degenerate lower states, the emission spectrum depends on the phase of the atomic dipole. The emission spectrum for the A -type three-level atom interacting with a squeezed coherent field is not only dependent on the squeezing degree r, but also on the phase angle 0. Finally we focus our attention on studying the emission spectrum of two atoms driven by a single-mode field in an ideal cavity. We showedthat the atomic emission spectrum is insensitive to the phase of field for the two atoms initially in the coherent superposition state tf/\\ = V2/2(j+,-) H?+}), when the two atoms is initially prepared in (fs*} = cos(0/2]+,+) + sm(0/2)ei'p-,-), the atomic emission spectrum is associated with not only the field photon-number distribution and the atomic populations, but also the phases of the field and the atomic dipole. Under an appropriate condition, the squeezed vacuum field can trap the two atoms inri).An analytical expression of emission spectrum for three-level atom interacted with two-mode cavity field is given. The effects of the initial state of system on the emission spectrum for three-level atom are explored. We clarified that if the three-level atom and the two-mode cavity field are all in the coherent superposition state, the different transition processes interfere each other, the emission spectrum exhibits phase sensitivity.Second, the phase properties of the two-mode SU(2) coherent field interacting with A-type three-level atom and the two-mode SU(1,1) coherent field interacting with two atoms are investigated. It is found that single-mode phase is all randomly distributed. The expressions of average value and variance of the phase difference and sum components are presented. We verified that under an appropriate condition the interference between the different transition processes makes counter balance, which induces the atom-field coupling system to be decoupled. The atomic population coherent trapping will take place.Finally, the atomic coherent population trapping is studied in a multilevel laser-induced continuum structure system including cascade two-photon processes by means of quasi-classical theory. The condition leading to the atomic coherent population trapping and the dark state are given explicitly. The effects of atomic initial state and the laser intensity on the populations distributed in the atomic bound statesare discussed. Influence of atomic coherence on Rydberg-atom stabilization is revealed. Then, the effects of the relative phase of the four lasers on the steady-state photoelectron spectrum in a two-channel ionization system in which the intermediate states are two sets of quasi-continua states are also investigated. If the intermediate states of the ionization channel i...