Ultracold neutral plasmas

Photoionization of samples of laser-cooled atoms has allowed the creation of ultracold neutral plasmas, accessing an unexplored plasma parameter regime. Among the phenomena that have been observed are a rapid expansion of the unconfined plasma, and recombination of the plasma into Rydberg atoms, even at very low plasma densities. The expanding plasma is a complex dynamic system, with adiabatic cooling, evaporative cooling, and recombination heating all occurring simuitaneously. Current experiments seek to determine the temperature evolution of the plasma that results from these competing processes.