William Daniel Phillips
active c. 1948, Wilkes-Barre, Pennsylvania, USA
American physicist who shared the 1997 Nobel Prize in Physics for laser cooling to sub-Doppler temperatures and atom trapping at NIST.
Born in Wilkes-Barre, Pennsylvania, Phillips studied at Juniata College and earned his PhD at MIT in 1976 on the magnetic moment of the proton in water — a measurement bearing on the fundamental constants. He joined NIST (then NBS) in 1978, where he demonstrated magnetic deceleration and trapping of neutral atoms and led the team that measured the first sub-Doppler laser cooling (1988) — sodium atoms colder than theory predicted, a puzzle solved by the polarization-gradient mechanism. His group later achieved record cold-atom collisions and fountain-clock work.
Nobel-winning work
At NIST in 1988 Phillips's group used time-of-flight measurements to show that sodium atoms in optical molasses reached ~40 μK — six times colder than the Doppler limit. The anomaly forced the discovery of polarization-gradient cooling (explained with Cohen-Tannoudji and Dalibard) and established that laser light could cool atoms into the microkelvin regime.
His group also developed the magnetic trap and early atom-optics tools (atom focusing, the 'atomic trampoline'), paving the way toward Bose–Einstein condensation, atomic fountains and precision clocks.
Workplaces: National Institute of Standards and Technology (NIST)
United States