Inelastic collisions in optically trapped ultracold metastable ytterbium.

We report measurement of inelastic loss in dense and cold metastable ytterbium (Yb[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 Yb[3P2] are produced at a density of 2 x 10(13) cm(-3) and temperature of 2 microK. We observe rapid two-body trap loss of Yb[3P2] and measure the inelastic collision rate constant 1.0(3) x 10(-11) cm3 s(-1). The existence of the fine-structure changing collisions between atoms in the 3P2 state is strongly suggested.