Number 279 (Story #1), July 15, 1996 by Phillip F. Schewe and Ben Stein GENERATING "SOUND WAVES" IN BOSE-EINSTEIN CONDENSATES : A NIST-University of Colorado team (contact Deborah Jin, 303-492-7784) and an MIT group (contact Marc-Oliver Mewes, 617-253-4178) have independently produced collective oscillations in BECs, collections of atoms that become so cold and so dense that the atoms essentially overlap and fall into a single quantum state. Aiming to study the fluid properties of this new state of matter, both teams wiggle BECs by adding a small oscillating magnetic field to the usual magnetic fields that trap the BEC. The researchers then turn off the perturbing field and let the BEC assume its natural oscillations. The resulting disturbances propagate through the BEC like sound waves traveling through air. The Colorado group observed one mode in which the BEC sloshes back and forth like a squeezed water balloon and another similar to a spiraling football. The MIT group found a pair of modes that resemble a sort of breathing motion of the condensate. Both teams found these excitations to be analogous to those in superfluid helium, and indeed the observed oscillation frequencies agree with those that emerge from theories that predict superfluidity for BECs. However, the researchers emphasize that more comprehensive studies of the fluid properties and excitation modes of BECs are needed to establish superfluidity. (D.S. Jin et al., Physical Review Letters, 15 July 1996; M.-O. Mewes et al, Physical Review Letters, 5 August 1996.)