Methods of sub-Doppler cooling include optical molasses, Sisyphus cooling, evaporative cooling, free space Raman cooling, Raman side-band cooling, resolved sideband cooling, polarization gradient cooling, electromagnetically induced transparency (EIT) cooling, and the use of a dark magneto-optical trap. These techniques can be used independently or combined in an experimental sequence, depending on the minimum temperature needed and specifications of the individual setup. For example, an optical molasses time-of-flight technique was used to cool sodium (Doppler limit T D ≈ ≈ 240 μ μ K ) to 43 ± ± 20 μ μ K .