Magneto-Optical Trapping of Ytterbium Atoms with a 398.9nm Laser

We report the realization of ytterbium magneto-optical trap (MOT) operating on the dipole-allowed ¹S₀-¹P₁ transition at 398.9nm. The MOT is loaded by a
slowed atomic beam produced by a Zeeman slower. All seven stable isotopes of Yb atoms could be trapped separately at different laser detuning values. Over 10^{7 174}Yb atoms are collected in the MOT, whereas the atom number of fermionic isotope ¹⁷¹Yb is roughly 2.3×10⁶ due to a lower abundance. Without the Zeeman slower, the trapped atom numbers are one order of magnitude lower. Both the even and odd isotopes are recognized as excellent candidates of optical clock transition, so the cooling and trapping of ytterbium atoms by the blue MOT is an important step for building an optical clock.