Radiation-Pressure Cooling of Bound Resonant Absorbers

We report the first observation of radiation-pressure cooling on a system of resonant absorbers which are elastically bound to a laboratory fixed apparatus. Mg ii ions confined in a Penning electromagnetic trap are cooled to 40 K by irradiating them with the 8- output of a frequency doubled, single- mode dye laser tuned to the low- frequency side of the Doppler profile on the ^2S₁₂^2P₃₂ (M₉=+12M₉=+32 or M₉=-12M₉=-32) transitions. Cooling to approximately 10^-3 K should be possible.