Mohammad Mohammadi

In this research, by using the green function approach of electromagnetic field quantization in a gauge with zero scalar potential, at the presence of a semi-infinite dielectric wall (which its dielectric function is an arbitrary complex function of frequency), the vector potential operators corresponding to normal polarization (known as the singlet part) and corresponding to the sum of parallel and longitudinal polarizations (known as the doublet part) are evaluated. Using the explicit from of the obtained vector potential operators in Fermi Golden rule, the spontaneous emission rate of an excited atom (with definite transition frequency and electric dipole moment) is calculated. Atoms with electric dipole moment parallel and perpendicular to the wall are investigated separately and for each orientation an expression for the spontaneous emission rate in terms of the distance to the wall and the dielectric function of the wall is obtained. Considering a Lorentzian model for the dielectric function of the wall, for each orientation, the variations of the spontaneous emission rate in terms of the distance to the wall are shown in same graphs. The limit of a perfect conducting wall is investigated and the agreement with previous works is shown.