Measurement of static electric dipole polarizabilities of lithium clusters: Consistency with measured dynamic polarizabilities

Static electric dipole polarizabilities of lithium clusters made of n (n=2- 22) atoms have been measured. The experiment consists of deflecting a colli mated cluster beam through a static inhomogeneous electric field. The stron g decrease per atom from Li to Li-3-Li-4 shows that electronic delocalizati on is reached for very small sizes. Moreover, directly measured polarizabil ities are consistent with photoabsorption data. They thus confirm unambiguo usly the ''missing'' optical strength in Lithium clusters. [S1050-2947(99)5 0301-6].