A PRELIMINARYMEASUREMENTOFh/mRb USINGULTRACOLDATOMS

We useBlochoscillations ina horizontal anda vertical movingstanding wave totransfer a large numberof photon recoils toatoms.Bymeasuring thephoton recoil of87Rb, usingvelocity selective Ramantransitions to select a subrecoil velocity class andtomeasurethefinal accelerated velocity class, we havedetermined h/mRb with arelative precision of0.4ppm