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| Ultracold
Neutral Plasmas
Over 99% of the visible matter in the universe exists as plasma, in which neutral atoms have been ionized to produce free electrons and ions. Traditionally, neutral plasmas are relatively hot, such as the solar corona (1,000,000 K), a candle flame (1000 K), or the ionosphere around our planet (300 K). Using techniques of laser cooling, which originated in the atomic physics community, it is now possible to create ultracold neutral plasmas at temperatures as low as about 1 K. In a table-top apparatus, laser light traps and cools about 1 billion neutral atoms to a thousandth of a degree above absolute zero. A second laser illuminates the cloud with photons with barely enough energy to ionize the atoms and create the plasma. Little is known about plasmas in this new regime. In addition to satisfying fundamental curiosity, experiments may shed light on the physics of dense plasmas in thermonuclear devices or the cores of gas giant planets.
Laser-Cooled Neutral Strontium The field of ultracold neutral gases has produced many exciting advances in the last decade, such as the creation of Bose-Einstein condensates and quantum-degenerate Fermi gases, the study of ultracold chemistry, and a host of high-tech applications. Laser-cooled strontium promises to impact all these areas. The Killian group recently completed construction of a laser-cooling apparatus for strontium that pushes the limits for this technique to higher density and lower temperature. The first application has been to perform photoassociative spectroscopy, in which a laser photon glues two colliding atoms together to form a molecule. The sensitivity of this process to the interactions between the atoms teaches us a great deal about chemistry at ultracold temperatures. We have already learned that one of the isotopes of strontium has ideal interactions for forming a Bose-Einstein condensate, which is a coherent form of matter analogous to a laser. These ultracold strontium samples have great potential to form the basis for ultra-precise clocks or interferometers that can be used to measure gravity and motion. Quantum optical effects in atomic gases may also lead to higher resolution lithographic techniques for producing integrated circuits, and we have a collaboration with Professor Karl Berggren in the Electrical Engineering Department at MIT to pursue these possibilities.
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To learn more, contact Professor Killian or stop by the lab in Dell Butcher Hall 100. Visitors are always welcome! |