Measurement of Radiative Decay and Cold Collision Trap Losses in Laser-Cooled Ytterbium

Ytterbium lattice frequency standard is an outstanding optical clock with a demonstrated relative frequency accuracy of 3.4·10 -16 , presently limited by the uncertainty on the blackbody radiation (BBR), lattice polarizabilities and cold collisions shifts. In particular the BBR shift is looming as a major component in the uncertainty budget of many optical frequency standards. In fact the uncertainty on BBR systematic shift in Ytterbium atoms is due both to experimental and theoretical limits in the knowledge of the atomic system: presently Ytterbium has the largest theoretical uncertainty on the BBR shift. Then, both for atomic physics and metrology, new measurementsof the Ytterbium atomic properties are strongly demanded, such as the determination of transition matrix elements, lifetimes, branching ratios, polarizabilities and hyperfine constants. In this work we present a set of new measurements for the radiative decay and for the cold collisions trap losses in laser-cooled Ytterbium atoms. These data are relevant to the blackbody radiation shift evaluation and to the coldcollisions shift theory