In general the transition dipole moment is a complex vector quantity that includes the phase factors associated with the two states.

In addition, the transition dipole moment depends on the geometries and relative phases of the initial and final states.

Giving the transition dipole moment:

The transition dipole moment is useful for determining if transitions are allowed under the electric dipole interaction.

The dot product includes a factor of , where is the angle between the polarization of the light and the transition dipole moment.

A basic, phenomenological understanding of the transition dipole moment can be obtained by analogy with a classical dipole.

This can be obtained using the transition dipole moment μ with the FGR and relationship between Einstein coefficients.

For example electric dipole which in turn are excited by optical phonons or fluid particle vibration, or transition dipole moments of electronic transitions.

For example, the transition from a bonding orbital to an antibonding orbital is allowed because the integral defining the transition dipole moment is nonzero.

FRET also depends on the donor-acceptor spectral overlap (see figure) and the relative orientation of the donor and acceptor transition dipole moments.

The SI unit of the transition dipole moment is the Coulomb-meter (Cm); a more conveniently sized unit is the Debye (D).

The Transition dipole moment or Transition moment, usually denoted for a transition between an initial state, , and a final state, , is the electric dipole moment associated with the transition between the two states.

When an atom or molecule interacts with an electromagnetic wave of frequency , it can undergo a transition from an initial to a final state of energy difference through the coupling of the electromagnetic field to the transition dipole moment.

Similarly, the coupling between an electromagnetic wave and an atomic transition with transition dipole moment depends on the charge distribution within the atom, the strength of the electric field, and the relative polarizations of the field and the transition.