The radiation and one - step absorption of the four - level atom is studied. Atom＇s motivated state is not stable, it inevitably disintegrate into the lower energy state, which makes the phenomenon of radiation. This paper is on the basis of theories of quantum mechanics and Kraus operator, utilizing the reducible density rectangular method to probe into the transformation of density matrix opposite angles element and non - opposite angles element of the four - level atom, which in the case of the radiation and one - step absorptio...
