Radiation-Pressure Cooling of Bound Resonant Absorbers

Abstract

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-μW output of a frequency doubled, single- mode dye laser tuned to the low- frequency side of the Doppler profile on the ${}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\leftrightarrow {}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ ($M_J=+\frac{1}{2}\leftrightarrow M_J=+\frac{3}{2}$ or $M_J=-\frac{1}{2}\leftrightarrow M_J=-\frac{3}{2}$) transitions. Cooling to approximately ${10}^{-3\mathrm{}}$ K should be possible.