 William Daniel Phillips

William Daniel Phillips developed experimental laser cooling and trapping of neutral chemical atoms. His work on optical molasses helped establish that real multilevel atoms could cool well below the simple Doppler cooling limit.

The decisive observable was the velocity spread after the sample was released. Independent ballistic measurements found sodium colder than the two-level model predicted, motivating additional cooling mechanisms involving atomic sublevels and wave polarization. His Nobel lecture connects this discrepancy with the development of reliable trapping and cooling methods.^[ref][ref]

William Daniel Phillips is an American physicist known for his work in the field of atomic physics, particularly for his contributions to laser cooling and trapping of atoms. He was awarded the Nobel Prize in Physics in 1997, along with Steven Chu and Claude Cohen-Tannoudji, for their development of methods to cool and trap atoms with laser light. This pioneering work has had a significant impact on various areas of science and technology, including quantum mechanics and the development of atomic clocks.