Longitudinal magnetic field effects in subDoppler cooling

Sub-Doppler laser cooling can be achieved in the absence of polarization gradients when a weak transverse magnetic field is used for mixing eigenstates of the light shift operator. By contrast, Zeeman shifts from magnetic fields Bell along the quantization axis can add or subtract with the light shifts of those states. Bell thus provides an additional degree of freedom for studying magnetic effects in laser cooling since the set of sinusoidal potentials that derives from the spatially periodic light shifts in a standing wave can be manipulated with the field. For example, with circularly polarized light, a finite Bell can switch the normal heating to cooling, and vice versa. We have done such experiments in the F = 3 → 4 transition of 85Rb at λ = 780 nm with diode laser light, and have shown that sub-Doppler heating and cooling can be interchanged with opposite longitudinal ed directions, in good agreement with this model. One application of such experiments is to characterize precisely the magnetic fields seen by the atoms along their trajectories in the beam