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An experimental researcher whose team observed Bose-Einstein condensation in sodium gas in 1995. A trap combining magnetic and optical forces allowed evaporative cooling to greatly increase the cloud’s phase-space density. Images after release developed two distinct components: a broad thermal cloud and a dense, elliptically expanding core. Their appearance made the transition measurable and provided an experimental system for studying the collective behavior of a dilute quantum gas.^[ref]

The 1995 sodium experiment combined laser cooling with a magnetic quadrupole trap and a repulsive optical plug protecting its field zero. Radio frequency evaporation preceded release and absorption imaging after time of flight. Lowering the evaporation cut produced broad thermal wings and a narrow core. Moving the plug changed the core's expansion orientation while the thermal distribution remained spherical: a control connecting the feature to confinement. Overlap of the two trapped pockets and residual switch-off acceleration limited quantitative shape comparisons; repulsive interactions affected expansion.^[ref]

Wolfgang Ketterle helped produce and investigate Bose-Einstein condensation in a dilute sodium gas. Cooling a trapped sample into the quantum-degenerate regime produced a population concentrated in a common low-energy state.

Expansion images distinguished the narrow condensed component from the broader thermal cloud. Subsequent experiments used coherence and collective motion to test how the macroscopic population behaves as a matter wave. His Nobel lecture connects the condensation apparatus with interference experiments and the atom laser.^[ref][ref]