Simien, CE, Chen YC, Gupta P, Laha S, Martinez YN, Mickelson PG, Nagel SB, Killian TC.
2005.
Absorption imaging of ultracold neutral plasmas, Apr. Ieee Transactions on Plasma Science. 33:540-541.
AbstractWe report optical absorption imaging of ultracold neutral plasmas. Imaging allows direct observation of the ion density profile and expansion of the plasma. The frequency dependence of the plasma's optical depth gives the ion absorption spectrum, which is broadened by the ion motion. We use the spectral width to monitor ion equilibration in the first 250 ns after plasma formation. On a microsecond time scale, we observe the radial acceleration of ions resulting from pressure exerted by the trapped electron gas.
Killian, TC, Chen YC, Gupta P, Laha S, Martinez YN, Mickelson PG, Nagel SB, Saenz AD, Simien CE.
2005.
Absorption imaging and spectroscopy of ultracold neutral plasmas, Jan 28. Journal of Physics B-Atomic Molecular and Optical Physics. 38:S351-S362.
AbstractAbsorption imaging and spectroscopy can probe the dynamics of an ultracold neutral plasma during the first few microseconds after its creation. Quantitative analysis of the data, however, is complicated by the inhomogeneous density distribution, expansion of the plasma and possible lack of global thermal equilibrium for the ions. In this paper, we describe methods for addressing these issues. Using simple assumptions about the underlying temperature distribution and ion motion, the Doppler-broadened absorption spectrum obtained from plasma images can be related to the average temperature in the plasma.
Nagel, SB, Mickelson PG, Saenz AD, Martinez YN, Chen YC, Killian TC, Pellegrini P, Cote R.
2005.
Photoassociative spectroscopy at long range in ultracold strontium, Mar 4. Physical Review Letters. 94
AbstractWe report photoassociative spectroscopy of Sr-88(2) in a magneto-optical trap operating on the S-1(0)-->P-3(1) intercombination line at 689 nm. Photoassociative transitions are driven with a laser red detuned by 600-2400 MHz from the S-1(0)-->P-1(1) atomic resonance at 461 nm. Photoassociation takes place at extremely large internuclear separation, and the photoassociative spectrum is strongly affected by relativistic retardation. A fit of the transition frequencies determines the P-1(1) atomic lifetime (tau=5.22+/-0.03 ns) and resolves a discrepancy between experiment and recent theoretical calculations.
Killian, TC, Chen YC, Gupta P, Laha S, Martinez YN, Mickelson PG, Nagel SB, Saenz AD, Simien CE.
2005.
Ultracold neutral plasmas, May. Plasma Physics and Controlled Fusion. 47:A297-A306.
AbstractUltracold neutral plasmas are formed by photo-ionizing laser-cooled atoms near the ionization threshold. Through the application of atomic physics techniques and diagnostics, these experiments stretch the boundaries of traditional neutral plasma physics. The electron temperature in these plasmas ranges from 1 to 1000 K and the ion temperature is around 1 K. The density can approach 10(11) cm(-3). Fundamental interest stems from the possibility of creating strongly coupled plasmas, but recombination, collective modes, and thermalization in these systems have also been studied. Optical absorption images of a strontium plasma, using the Sr+ S-2(1/2) -> P-2(1/2) transition at 422 mn, depict the density profile of the plasma, and probe kinetics on a 50 ns time-scale. The Doppler-broadened ion absorption spectrum measures the ion velocity distribution, which gives an accurate measure of the ion dynamics in the first microsecond after photo-ionization.
Mickelson, PG, Martinez YN, Saenz AD, Nagel SB, Chen YC, Killian TC, Pellegrini P, Cote R.
2005.
Spectroscopic determination of the s-wave scattering lengths of Sr-86 and Sr-88, Nov 25. Physical Review Letters. 95
AbstractWe report the use of photoassociative spectroscopy to determine the ground-state s-wave scattering lengths for the main bosonic isotopes of strontium, Sr-86 and Sr-88. Photoassociative transitions are driven with a laser red detuned by up to 1400 GHz from the S-1(0)-P-1(1) atomic resonance at 461 nm. A minimum in the transition amplitude for Sr-86 at -494 +/- 5 GHz allows us to determine the scattering lengths 610a(0)< a(86)< 2300a(0) for Sr-86 and a much smaller value of -1a(0)< a(88)< 13a(0) for Sr-88.