title: Using higher ionization states to increase Coulomb coupling in an ultracold neutral plasma.
abstract: We report measurements and simulations of the time-evolving rms velocity distribution in an ultracold neutral plasma. A strongly coupled ultracold neutral Ca+ 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 Ca+-Ca2+ 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 Γ increases by a factor of 1.4 to a maximum value of 3.6. A pure Ca2+ plasma would have Γ=6.8, moving these strongly coupled systems closer to the regime of liquid-like correlations.
authors: Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA.
authors: M
authors: M
authors: Lyon
authors: Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA.
authors: S D
authors: SD
authors: Bergeson
authors: New Mexico Consortium, Los Alamos, New Mexico 87544, USA.
authors: A
authors: A
authors: Diaw
authors: New Mexico Consortium, Los Alamos, New Mexico 87544, USA.
authors: M S
authors: MS
authors: Murillo