# Electric dipole transition

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**Electric dipole transition** is the dominant effect of an interaction of an electron in an atom with the electromagnetic field.

Following,^{[1]} consider an electron in an atom with quantum Hamiltonian , interacting with a plane electromagnetic wave

Write the Hamiltonian of the electron in this electromagnetic field as

Treating this system by means of time-dependent perturbation theory, one finds that the most likely transitions of the electron from one state to the other occur due to the summand of written as

**Electric dipole transitions** are the transitions between energy levels in the system with the Hamiltonian .

Between certain electron states the electric dipole transition rate may be zero due to one or more selection rules, particularly the angular momentum selection rule. In such a case, the transition is termed *electric dipole forbidden*, and the transitions between such levels must be approximated by *higher-order transitions*.

The next order summand in is written as

and describes magnetic dipole transitions.

Even smaller contributions to transition rates are given by higher electric and magnetic multipole transitions.