= William Daniel Phillips
{c}
{tag=Physicist}
{wiki}
= William D. Phillips
{c}
{synonym}
<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.<Observation of Atoms Laser Cooled below the Doppler Limit by Paul D. Lett and others>[Abstract: sodium molasses and complementary ballistic thermometry]{ref}<Nobel Lecture: Laser cooling and trapping of neutral atoms by William D. Phillips>[Sub-Doppler cooling and experimental development]{ref}
\Image[https://commons.wikimedia.org/wiki/Special:Redirect/file/William%20D.%20Phillips.jpg?width=250]
{title=Portrait of <William Daniel Phillips>}
{description=Markus Pössel (Mapos). https://creativecommons.org/licenses/by-sa/3.0/[CC BY-SA 3.0], via Wikimedia Commons.}
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