The Formalism For Energy Changing Rate Of An Accelerated Atom Coupled With Electromagnetic Vacuum Fluctuations

Spontaneous emission is the process that electron jumps from excited state to ground state spontaneously,and emits a photon in the case of no external optical field.It is one of the most important features of atoms.Spontaneous excitation is the process that electron jumps from ground state to excited state,and absorbs a photon without external optical field.For static atom in Minkowski spacetime,there is spontaneous emission and no spontaneous excitation.But for aomt in acceleration or in curved spacetime,spontaneous excitation can occurs.The physical mechanisms of spontaneous emission and spontaneous excitation can all attribute to vacuum fluctuations and radiation reaction.Audretsch and Muler were the first to use a method of demanding symmetric operator ordering of atom and field variables to study the rate of variation of the atomic energy for an atom interacting with a scalar field.Meanwhile,they used rate equations and the average of energy to calculate the Einstein A coefficients that are just spontaneous emission rate and spontaneous excitation rate.Later,Passante and Zhu et al.generalized their works to the case of atom interacting with the electromagnetic field and they investigated the the rate of variation of the atomic energy for accelerated atom.In this paper,we will study the structure of the rate of variation of the atomic energy for an arbitrary stationary motion of the atom in interaction with a quantum electromagnetic field.In this formalism,we makes clear the contribute of vacuum fluctuations and radiation reaction to the total rate of variation of the atomic energy,thus the physical meaning of the total rate of change of the energyis explicit.Then based on this formalism,we deduce the general expression of spontaneous emission rate and spontaneous excitation rate of atom.In the case of thermal bath,we also give the general expression of the total emission rate and excitation rate.Finally,the total rate of change of the energy,Einstein coefficients and total emission rate and excitation rate of the atom near a plate with finite temperature or acceleration are calculated.