Radiative Energy Shifts Of An Atom Coupled To The Derivative Of A Scalar Field Near A Reflecting Boundary

In quantum radiation theory,spontaneous emission is attributed to vacuum fluctuations and radiation reaction.However,generally speaking,there exists ambiguity in thc scparation of the two effects.Dalibard J,Dupont-Roc J and Cohen-Tannoudji demonstrated that if we choose a symmetric ordering for the operators of the field and the atom,then the distinct contributions of vacuum fluctuations and radiation reaction to the rate of change of an atomic observable are Hermitian and able to possess independent physical meaning,and thus resolving the ambiguity. This scheme of separating two contributions is known as the DDC formalism.In this thesis,we first introduce the DDC formalism and then give a brief review of the existing works on both the spontaneous emission and energy level shifts of a two-level atom in monopole interaction with a massless scalar field,and those in dipole interaction with the derivative of the field using the DDC formalism.On the base of the above review,we study the radiative energy level shifts of a two-level atom coupled to the derivative of a quantum real massless scalar field near a reflecting boundary.We separate the contributions of vacuum fluctuations and radiation reaction to the level shifts using the DDC formalism.Our results show that,when the atom's distance from the boundary,z,is very large,the energy level shift of the excited state is an oscillating function of the atom's distance from the boundary and it could either be positive or negative,while that of the ground state is always positive and no longer oscillate.However,when the atom's distance from the boundary,z,is very small,the energy level shift is no longer oscillatory but always positive no matter if the atom is the ground state or the excited one.Our research also indicates that the energy level shift of the ground state behaves like 1/z~4 when the atom's distance from the boundary,z,is very large,while it does like 1/z~3 when z is very small.Finally,we conclude with a summary of our work and an outlook for possible future research.