Laser excitation dynamics of atomic and molecular clusters in free jets

The study of atomic and molecular clusters constitutes a rapidly growing cross-disciplinary field of research, whose current advances depend critically on the utilization of new laser and molecular beam techniques. This article surveys current advances in the production, state preparation, and size-separation of clusters using pulsed-laser and molecular beam techniques. Laser photoexcitation experiments are used to probe the unique dynamics of clusters using both high resolution spectroscopy and photo-fragmentation measurements. Examples given are the discovery of the adiabatic pseudorotation in excited Na3, and the search for ion-pair formation in the excitation of microscopic liquid drops. A general spectroscopic approach to the low-energy elementary excitations of metal clusters is presented.