200 research outputs found
Recombination fluorescence in ultracold neutral plasmas
We present the first measurements and simulations of recombination
fluorescence in ultracold neutral plasmas. In contrast with previous work,
experiment and simulation are in significant disagreement. Comparison with a
recombination model suggests that the disagreement could be due to the high
energy portion of the electron energy distribution or to large energy changes
in electron/Rydberg scattering. Recombination fluorescence opens a new
diagnostic window in ultracold plasmas because it probes the deeply-bound
Rydberg levels, which depend critically on electron energetics
Measurement and simulation of laser-induced fluorescence from non-equilibrium ultracold neutral plasmas
We report new measurements and simulations of laser-induced fluorescence in
ultracold neutral plasmas. We focus on the earliest times, when the plasma
equilibrium is evolving and before the plasma expands. In the simulation, the
ions interact via the Yukawa potential in a small cell with wrapped boundary
conditions. We solve the optical Bloch equation for each ion in the simulation
as a function of time. Both the simulation and experiment show the initial
Bloch vector rotation, disorder-induced heating, and coherent oscillation of
the rms ion velocity. Detailed modeling of the fluorescence signal makes it
possible to use fluorescence spectroscopy to probe ion dynamics in ultracold
and strongly coupled plasmas
Measurement and simulation of laser-induced fluorescence from non-equilibrium ultracold neutral plasmas
We report new measurements and simulations of laser-induced fluorescence in
ultracold neutral plasmas. We focus on the earliest times, when the plasma
equilibrium is evolving and before the plasma expands. In the simulation, the
ions interact via the Yukawa potential in a small cell with wrapped boundary
conditions. We solve the optical Bloch equation for each ion in the simulation
as a function of time. Both the simulation and experiment show the initial
Bloch vector rotation, disorder-induced heating, and coherent oscillation of
the rms ion velocity. Detailed modeling of the fluorescence signal makes it
possible to use fluorescence spectroscopy to probe ion dynamics in ultracold
and strongly coupled plasmas
Ultracold neutral plasma expansion in two dimensions
We extend an isothermal thermal model of ultracold neutral plasma expansion
to systems without spherical symmetry, and use this model to interpret new
fluorescence measurements on these plasmas. By assuming a self-similar
expansion, it is possible to solve the fluid equations analytically and to
include velocity effects to predict the fluorescence signals. In spite of the
simplicity of this approach, the model reproduces the major features of the
experimental data
Fluorescence measurements of expanding strongly-coupled neutral plasmas
We report new detailed density profile measurements in expanding
strongly-coupled neutral plasmas. Using laser-induced fluorescence techniques,
we determine plasma densities in the range of 10^5 to 10^9/cm^3 with a time
resolution limit as small as 7 ns. Strong-coupling in the plasma ions is
inferred directly from the fluorescence signals. Evidence for strong-coupling
at late times is presented, confirming a recent theoretical result.Comment: submitted to PR
- …