Sub-Doppler laser cooling of potassium atoms
  We investigate sub-Doppler laser cooling of bosonic potassium isotopes, whose small hyperfine splitting has so far prevented cooling below the Doppler temperature. We find instead that the combination of a dark optical molasses scheme that naturally arises in this kind of systems and an adiabatic ramping of the laser parameters allows to reach sub-Doppler temperatures for small laser detunings. We demonstrate temperatures as low as 25(3)microK and 47(5)microK in high-density samples of the two isotopes 39K and 41K, respectively. Our findings will find application to other atomic systems. 
M. Landini, S. Roy, L. Carcagni', D. Trypogeorgos, M. Fattori, M.   Inguscio, and G. Modugno
physics.atom-ph cond-mat.quant-gas