Diagrammatic perturbation theory of multiphoton transitions

Abstract

The interaction of a molecule with a quantized electromagnetic field is described within the framework of formal scattering theory. It is shown that the probability of multiphoton molecular transitions may then be represented in a particularly simple way by diagrams. Rules for constructing and interpreting these diagrams are described. Two forms of interaction potential are employed, namely, the standard form of non-relativistic limit of the Dirac equation, and an alternative formulation due to Richards [12]. The advantages of the alternative form are shown to be that terms which are bilinear in the field may be neglected, and that the remaining terms represent the multipole moment interactions of the molecule with the quantized field.