Number 338 (Story #1), September 25, 1997 by Phillip F. Schewe and Ben Stein|
IN A GRAVITO-OPTICAL SURFACE TRAP (GOST), cesium atoms, cooled first in a magneto-optical trap (MOT, which employs magnetic fields and laser beams to confine and cool atoms), are allowed to fall downwards onto a prism. When the atoms strike the prism, they are reflected upwards by the electromagnetic fields associated with "evanescent waves" which arise from a beam of laser light grazing the prism from beneath. The atoms are not only reflected, but lose some of their energy to the waves. After several bounces, the atoms collect in a chilled, essentially two-dimensional, cloud. In this way physicists at the Max-Planck Institute in Heidelberg (Rudolf Grimm, email@example.com) cooled Cs atoms from a temperature of 10-15 micro-K (in a MOT) down to 3 micro-K.The GOST approach might be helpful in producing Bose- Einstein condensates because (1) it is able to trap a much higher density of atoms than is possible with MOT's, thus creating a better starting point for the next stage in the Bose- Einstein process, evaporative cooling (see Update 305); (2) it is effective in trapping the atoms in all their magnetic varieties (some atoms, whose magnetic orientation is altered during collisions, would otherwise be lost from the trap); and (3) it might offer the chance to study 2-dimensional condensates since the atoms start out in a planar configuration. (Ovchinnikov et al., Physical Review Letters, 22 Sept.; see figure at Physics News Graphics.) By the way, the first report of a Bose-Einstein Condensate in a European lab comes from last week's European Research Conference on Quantum Optics at Castelvecchio Pascoli in Italy. Gerhard Rempe of the University of Konstanz (firstname.lastname@example.org) gave preliminary evidence for a rubidium-87 condensate in a "Ioffe-Pritchard" trap.