  We study laser cooling of atomic gases by collisional redistribution, a
technique applicable to ultradense atomic ensembles at a pressure of a few
hundred bar. Frequent collisions of an optically active atom with a buffer gas
shift atoms into resonance with a far red detuned laser beam, while spontaneous
decay occurs close to the unperturbed resonance frequency. In such an
excitation cycle, a kinetic energy of the order of the thermal energy kT is
extracted from the sample. Here we report of recent experiments investigating
the cooling of a potassium-argon gas mixture, which compared to an
rubidium-argon mixture investigated in earlier experiments has a smaller fine
structure of the optically active alkali atom. We observe a relative cooling of
the potassium-argon gas mixture by 120 K.
