False-color image of cold cesium atoms in a magneto-optical trap at the JPL Laser Cooling Facility
One of the most exciting developments in physics over the past 15 years has been the use of lasers to produce ultra-cold temperatures samples of neutral and charged atoms. Three of the leaders in this field were awarded the 1997 Nobel prize in physics. The very low temperatures obtainable by these techniques (as low as 1 millionth of a degree above absolute zero) permit one to perform extremely precise spectroscopic measurements free from most perturbations and with very long interaction times. For these reasons, laser cooling is being employed in the latest generation of neutral atom clocks, yielding dramatic improvements in precision. The major limitation on the interaction time obtainable arises due to the effect of gravity. Other applications of laser cooling involve the study of the novel behavior of very cold gases of atoms. At very low temperatures, for example, atoms confined within interfering pairs of lasers form an ordered array, called an optical lattice. By combining laser cooling with evaporative cooling, scientists have recently been able to study a purely quantum form of matter known as a Bose-Einstein condensate, and the researchers that first achieved this new state of matter were awarded the 2001 Nobel prize in physics. This work lead to the development of a preliminary version of a new device called an atom laser, which produces coherent, intense beams of atoms, much as a conventional laser produces beams of light.
Because of the significant, and often detrimental, effect that gravity plays in many laser cooling experiments, it is natural to consider whether the next generation of experiments should be carried out in a microgravity environment, such as is found on the International Space Station (ISS), or the space shuttle. For this reason, the NASA Microgravity Research Division has begun the Laser Cooling and Atomic Physics discipline, as part of its Fundamental Physics program. A number of ground based research programs have been funded, at universities and government research labs, each with an eye to determining just what research could most profitably be performed in a microgravity environment, and what the obstacles to such experiments would be. Flight Development grants have been awarded to researchers at Penn State University and the National Institute of Standards and Technology.
