Magneto–optical trap for neutral mercury atoms

Due to the low sensitivity to the blackbody radiation, neutral mercury is a good candidate for the most accurate optical lattice clock. Here we report the observation of cold mercury atoms in a magneto–optical trap (MOT). Because of the high vapor pressure at room temperature, the mercury source and the cold pump were cooled down to -40 ℃ and -70 ℃, respectively, to keep the science chamber in ultra-high vacuum of 6×10^-9 Pa. Limited by the power of the UV cooling laser, the one beam folded MOT configuration was adopted, and 1.5×10⁵ Hg-202 atoms were observed in the fluorescence detection.