Temperature Oscillations in Ultracold Plasmas

Although most plasmas exist at temperatures above that needed for ionization, it is now possible to create neutral plasmas with temperatures in the microKelvin range by rapid photoionization of a very cold gas. Because of their very low temperatures, such plasmas have Coulomb coupling parameters (ratio of potential to kinetic energy) as high as $\Gamma\sim 300,000$. Predictions of ultracold plasma behavior [Murillo, PRL {\bf 76}, 115003 (2001)] show that rapid heating occurs as the plasma correlates to form an equilibrium moderately coupled plasma. This prediction has recently been experimentally verified [Chen {\it et al.}, PRL {\bf 93}, 265003 (2004)] and, in addition, strong oscillations in the temperature were observed. I will discuss the basics of ultracold plasmas, the rapid heating mechanism, and give some insight into the temperature oscillations.