Copyright by Kirsten Viering 2006 - Raizen Lab - The University of ...

transition. Therefore only atoms in the |F = 2〉 ground state will be excited by our laser
and start fluorescing until they finally decay into the |F = 1〉 state. Ususally, a repump
laser, tuned to the |3 2 S1/2, F = 1〉 → |3 2 P3/2, F = 2〉 transition, is used to transfer atoms
out of the dark state back to the |F = 2〉 ground state.
Let us assume now all atoms start in the |F = 1〉 ground state. In a direct
transition using a radio frequency pulse spatial resolution can be achieved by shifting
the energy levels of the two hyperfine ground states by applying a magnetic field
gradient. This leads to a spatially varying resonance frequency ω0. By tuning the
frequency of the radio field one can select a small region around x0 in which the atoms
will make a transition, if a pulse with the appropriate intensity and duration is applied.
A simplified scheme of the one-photon transition is shown in fig. 5.1, where we have
assumed that only the final state | f 〉 is dependant on the magnetic field. The resolution
is given by the width of the atomic distribution that is excited around a particular x0.
Figure 5.1: Simplified scheme of a resonant transition with spatial resolution; the
resonance frequency ω0 is space-dependant, i.e. the resonance frequency ω0 at x0 is not
in resonance at point x. For simplicity we have assumed that only the final state | f 〉 is
dependant on the magnetic field.
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