Abstract
We report measurements and simulations of the time-evolving rms velocity distribution in an ultracold neutral plasma. A strongly coupled ultracold neutral plasma is generated by photoionizing laser-cooled atoms close to threshold. A fraction of these ions is then promoted to the second ionization state to form a mixed plasma. By varying the time delay between the first and the second ionization events, a minimum in ion heating is achieved. We show that the Coulomb strong-coupling parameter increases by a factor of 1.4 to a maximum value of 3.6. A pure plasma would have , moving these strongly coupled systems closer to the regime of liquid-like correlations.
- Received 6 November 2014
DOI:https://doi.org/10.1103/PhysRevE.91.033101
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