We are studying plasmas at sub-Kelvin temperatures, created by photo-ionizing laser-cooled calcium atoms.  This "ultra-cold plasma" is strongly coupled, meaning that the average nearest-neighbor Coulomb energy is greater than the average thermal energy of particles in the plasma.  At sufficiently low temperatures, the plasma may become quantum-mechanically degenerate, meaning that the average deBroglie wavelength of the electrons is the same size as the distance between electrons.

We use calcium to create this plasma because the energy level scheme in Ca is favorable for laser cooling and trapping.  Also, the resonance transition in Ca⁺ is accessible to standard laser technology, so that when plasma is created, the density and temperature of the ion system can be probed using tools from the laser cooling community.  The study of ultracold plasmas and dense Rydberg systems at low temperatures is in its infancy, with the first papers appearing in 1998.

Other experimental groups in the US working on related projects include Steve Rolston's group at the University of Maryland, Tom Killian's group at Rice University, Ed Eyler and Phil Gould at the University of Connecticut, Georg Raithel's group at the University of Michigan, Michael Noel's group at Bryn Mawr, and Tom Gallagher's group at the University of Virginia.

This work is based on research supported in part by Brigham Young University, the Research Corporation, and the National Science Foundation (under grant no. PHY-9985027).
 

Last modified 2 January 2006