Ultracold neutral plasmas

The advent of samples of laser-cooled atoms at microkelvin temperatures combined with photo-ionization provided a means to create neutral plasmas at temperatures as low as 1 K. In this talk I will review the fifteen-year history of the field of ultracold neutral plasmas, which resides at the intersection of atomic physics and plasma physics. A wide variety of phenomena have been investigated, including plasma creation, expansion dynamics, temperature evolution, collisional properties, and collective modes. Because of the low temperatures, recombination into Rydberg atoms has been shown to be important, as well as plasma formation from Rydberg gases. While mechanisms conspire to keep the electrons weakly coupled, the ions have been shown to reach into the strong coupling regime. These ultracold plasmas extend the parameter range of plasma physics, and offer a new window into strong coupling phenomena, usually associated with high energy density plasmas.