Record-breaking cold trap for pinning atoms.It's getting bitterly cold and unnaturally crowded in atom traps. A year ago, a group of researchers at the National Institute of Standards and Technology National Institute of Standards and Technology, governmental agency within the U.S. Dept. of Commerce with the mission of "working with industry to develop and apply technology, measurements, and standards" in the national interest. in Gaithersburg, Md., chilled cesium cesium (sē`zēəm) [Lat.,=bluish gray], a metallic chemical element; symbol Cs; at. no. 55; at. wt. 132.9054; m.p. 28.4°C;; b.p. 669.3°C;; sp. gr. 1.873 at 20°C;; valence +1. atoms to 700 nanokelvins (SN: 9/10/94, p.175). Now, Eric A. Cornell and his coworkers at the Joint Institute for Laboratory Astrophysics (JILA JILA Joint Institute for Laboratory Astrophysics (Space) ) at the National Institute of Standards and Technology and the University of Colorado University of Colorado may refer to:
Using a novel technique for cooling rubidium rubidium (r  bĭd`ēəm), metallic chemical element; symbol Rb; at. no. 37; at. wt. 85.4678; m.p. 38.89°C;; b.p. 686°C;; sp. gr. 1.53 at 20°C;; valence +1. atoms in a new type of magnetic trap, the researchers recorded 200 nK as the temperature of a tightly confined atomic gas. At this temperature, rubidium atoms move with an average speed of only 4 millimeters per second. The JILA team reported its achievement last week at a quantum electronics and laser science conference held in Baltimore. Cornell and his colleagues used a specially designed, nonuniform magnetic field to trap a large number of cold rubidium atoms in a tiny volume. Atoms in such a trap travel at widely varying speeds, often changing velocities after each collision. By gradually lowering the trap's magnetic field to let the fastest (or hottest) atoms escape, leaving behind the slower (or colder) atoms, the researchers steadily decreased the temperature of the confined atomic gas. A similar evaporative process is responsible for cooling a hot drink. An additional field adjustment kept the cold atoms trapped. Eventually, Cornell's group packed about 50,000 slow-moving atoms into a volume only 23 micrometers across. The researchers measured the average atomic speed by shining laser light on the atoms to make them fluoresce fluo·resce intr.v. fluo·resced, fluo·resc·ing, fluo·resc·es To undergo, produce, or show fluorescence. [Back-formation from fluorescence. and then videotaping the cloud motion viewed through a microscope. They could then infer the temperature. The existence of such frigid atomic clouds may prove useful for high-precision experiments involving atomic clocks and for improved types of spectroscopy, the researchers say. Because there is no theoretical lower limit to the temperature of atoms confined in the type of trap used by the researchers, further advances in evaporative cooling may bring atoms close enough to absolute zero that they will undergo Bose-Einstein condensation into a novel quantum state of matter. Originally predicted many decades ago by Albert Einstein and Satyendra Nath Bose Noun 1. Satyendra Nath Bose - Indian physicist who with Albert Einstein proposed statistical laws based on the indistinguishability of particles; led to the description of fundamental particles that later came to be known as bosons Bose, Satyendra N. Bose , such a condensate arises when a clump of atoms gets so cold and dense that all its constituent atoms congeal con·geal v. con·gealed, con·geal·ing, con·geals v.intr. 1. To solidify by or as if by freezing: "My aim . . . was to take the Hill by storm before . . . into a single quantum state. No one has yet observed this peculiar state, and physicists aren't sure how such a condensate will behave if and when it is finally found. -- I. Peterson |
|
||||||||||||||||||||
Printer friendly
Cite/link
Email
Feedback
Reader Opinion