My research centers around the interaction of radiation with ions. I use tunable laser photodetachment to probe electron correlation and to investigate dipole-bound states of negative ions. I use negative-ion photoelectron spectroscopy to determine electron affinities and structures of radicals and metal clusters. I study the transition from gas phase to condensed phase by means of photodissociation and photodetachment of cold cluster ions by using nanosecond and picosecond lasers. I study ultrafast molecular rearrangement dynamics using pump-probe, and photodetachment-photoionization of negative ions.