Inelastic Collisions in Optically Trapped Ultracold Metastable Ytterbium

We report measurement of inelastic loss in dense and cold metastable ytterbium (Yb½ 3P2 ). Use of an optical far-off-resonance trap enables us to trap atoms in all magnetic sublevels, removing m-changing collisional trap loss from the system. Trapped samples of Yb½ 3P2 are produced at a density of 2 1013 cm3 and temperature of 2 K. We observe rapid two-body trap loss of Yb½ 3P2 and measure the inelastic collision rate constant 1:0ð3Þ 1011 cm3 s1. The existence of the fine-structure changing collisions between atoms in the 3P2 state is strongly suggested.Physic