Steven Rolston<br>

Atomic Physics Division, NIST<br>

<i>Ultracold Neutral Plasmas</i><p>

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A laser-cooled sample of atoms (T ~ 10 microkelvin) photoionized just above
threshold creates an ultracold neutral plasma. The unconfined plasma then
expands into a vacuum, governed by a wide variety of effects. Evaporative
cooling, adiabatic cooling, and recombination heating all act simultaneously
to regulate the state of the system. A substantial fraction of the plasma
recombines into Rydberg atoms. In addition, a laser-cooled sample of atoms
excited to high Rydberg levels spontaneously turns into an ultracold
plasma. These systems reside at the interface between single-particle atomic
physics and the collective behavior of plasma physics. I will discuss recent
results at NIST and elsewhere as well as theoretical efforts to understand
this complex, correlated, dynamic system.


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