Cooling of Sr to high phase-space density by laser and sympathetic   cooling in isotopic mixtures
  Based on an experimental study of two-body and three-body collisions in ultracold strontium samples, a novel optical-sympathetic cooling method in isotopic mixtures is demonstrated. Without evaporative cooling, a phase-space density of $6\times10^{-2}$ is obtained with a high spatial density that should allow to overcome the difficulties encountered so far to reach quantum degeneracy for Sr atoms. 
G. Ferrari, R. E. Drullinger, N. Poli, F. Sorrentino, and G. M. Tino