A simplest possible scheme for sub-Doppler laser cooling

The simplest angular momentum schemes that permit sub-Doppler cooling have 4 levels, and one example is an F = 1 → 0 transition in either a linearly or circularly polarized standing wave with a weak transverse magnetic field. The 28% abundant 87Rb isotope has an F = 1 → 0 transition that is ideal for studying this case. Magnetically induced laser cooling can reduce atomic KE to below the peaks of the spatially periodic potential seen by the atoms as a result of their light shifts, thus channeling them between the planes of the standing wave. Furthermore, their deBroglie wavelengths become comparable to the channel size so that the motion is quantized in these half-wavelength sized optical traps. This F = 1 → 0 transition produces only one light-shifted level, and thus only one ground state sublevel that can support bound quantized states. An rf-induced transition that would change the populations of the quantum vibrational states of this potential would be particularly easy to interpret, and would be subject to easily understood Zeeman shifts in a longitudinal field. We are presently studying this problem