Optical pumping of ultracold thulium atoms to a lower level of the clock transition and study of their depolarisation

The atomic energy levels corresponding to states with the zero projection of the total angular momentum have a weak sensitivity to certain sources of shifts and, therefore, are widely used in precision spectroscopy. The optical pumping of ultracold thulium atoms to the ground state level with the zero projection of the total angular momentum is described. The population dynamics of this state due to magnetic dipole − dipole interaction in an external magnetic field is studied.