Experimental and theoretical lifetimes in YbIII

Lifetimes of three levels belonging to the configuration 4f(13)5d with J = 1 in Yb III have been measured for the first time using the time-resolved l aser-induced fluorescence method. Experimental transition probabilities hav e been deduced for the transitions between the levels studied and the groun d state. The comparison of the experimental lifetimes with theoretical data , deduced within the relativistic Hartree-Fock (HFR) approach, underlines t he dramatic importance of an adequate consideration of core-polarization ef fects in the theoretical model and the sensitivity of one of the lifetime v alues to small correlation effects.