  We describe experiments on the laser cooling of both helium-rubidium and
argon-rubidium gas mixtures by collisional redistribution of radiation.
Frequent alkali-noble gas collisions in the ultradense gas, with typically
200\,bar of noble buffer gas pressure, shift a highly red detuned optical beam
into resonance with a rubidium D-line transition, while spontaneous decay
occurs close to the unshifted atomic resonance frequency. The technique allows
for the laser cooling of macroscopic ensembles of gas atoms. The use of helium
as a buffer gas leads to smaller temperature changes within the gas volume due
to the high thermal conductivity of this buffer gas, as compared to the heavier
argon noble gas, while the heat transfer within the cell is improved.
