Number 272 (Story #1), May 23, 1996 by Phillip F. Schewe and Ben Stein|
ADVANCES IN BOSE-EINSTEIN CONDENSATES: First produced last year by a NIST-University of Colorado group, Bose-Einstein condensates (BECs) comprise a new state of matter in which gas atoms, cooled to near-absolute-zero temperatures, overlap with each other and collapse into a common quantum state, where they behave essentially as a single "superparticle." At the American Physical Society Division of Atomic, Molecular and Optical Physics meeting last week at the University of Michigan, Wolfgang Ketterle and his colleagues at MIT (617-253-6815) announced that they had produced a Bose-Einstein condensate of 5 million atoms, 10 times bigger than any previous BEC. At 150 microns long and 8 microns wide, the condensate was large enough to be directly observed for the first time. The MIT researchers shone some laser light onto the condensate and imaged the scattered light with a sensitive camera. What they saw was a direct image of an atomic matter wave with a half wavelength of 150 microns. Performing the first study of the BEC's mysterious optical properties, the MIT group found that the sodium condensate acts as a lens and that the light scattered off the condensate is anisotropic: in other words, it scatters light preferentially in certain directions. To produce the condensate, the researchers used a combination of lasers and magnetic fields in a special configuration in which cloverleaf-shaped coils generate magnetic fields that tightly confine the atoms while allowing the setup's 11 lasers to pass easily into the trapping region.