The coherence of two level atom being put in a thermal reservoir with a Kerr like medium is investigated. The time evolution properties of non opposite angle element of two level atom′s reducible density rectangular array is obtained. Coherence properties of two level atom is studied in degenerate two photon processes when the two level atom interacts with an driving field in the external environment. When two level atom′s coherence is maintained, the theoretical result demonstrates that time evolution of an external driving field is closely ...
