- Rabi frequency
The Rabi frequency for a given atomic transition in a given light field gives the strength of the coupling between the light and the transition.
Rabi flopping between the levels of a 2-level system illuminated with resonant light, will occur at the Rabi frequency. The Rabi frequency is asemiclassical concept as it is based on a quantum atomic transition and a classical light field.In the context of a
nuclear magnetic resonance experiment, the Rabi frequency is the nutation frequency of a sample's net nuclear magnetization vector about a radiofrequency field. (Note that this is distinct from the Larmor frequency, which characterizes the precession of a transverse nuclear magnetization about a static magnetic field.)Definition
:
where is the
transition dipole moment for the transition and is the vectorelectric field amplitude which includes thepolarization .The numerator has dimensions of energy, dividing by gives an
angular frequency . Although , one cannot assume that as may be complex, as in the case ofcircularly polarized light .cite book| title = Lasers | edition = | last = Milonni | first = Peter W. | coauthors = Eberly, Joseph H. | year = 1998| publisher = John Wiley & Sons| id = ISBN 0-471-62731-3| pages = p. 191]By analogy with a classical
dipole , it is clear that an atom with a large dipole moment will be more susceptible to perturbation by electric and magnetic fields. Thedot product includes a factor of , where is the angle between the polarization of the light and the transition dipole moment. When they are parallel or antiparallel the interaction is strongest, when they are perpendicular there is no interaction at all. The vector electric field amplitude defines both the intensity and the polarization of the light.Generalized Rabi frequency
For light that is off resonance with a transition, it is common to define the "generalized Rabi frequency" .
Rabi flopping actually occurs at the generalized Rabi frequency.:
where is the "detuning", a measure of how far the light is off resonance with the transition.
ee also
*
Rabi cycle
*Vacuum Rabi oscillation References
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