Willem Keesom
Willem Keesom in 1926
Born	21 June 1876 (1876-06-21) Texel, Netherlands
Died	3 March 1956(1956-03-03) (aged 79) Leiden, Netherlands
Known for	helium
Scientific career
Fields	physics
Doctoral advisor	Johannes Diderik van der Waals

Willem Hendrik Keesom (/ˈkeɪsoʊm/^[1][2]) (21 June 1876,Texel – 3 March 1956,Leiden) was a Dutchphysicist who, in 1926, invented a method to freeze liquidhelium.He also developed the first mathematical description ofdipole–dipole interactions in 1921. Thus, dipole–dipole interactions are also known asKeesom interactions.He was previously a student ofHeike Kamerlingh Onnes, who had discoveredsuperconductivity (a feat for which Kamerlingh Onnes received the 1913Nobel Prize in Physics).

He also discovered thelambda point transition specific-heat maximum between helium-I and helium-II in 1930.^[3]

In 1924 he became member of theRoyal Netherlands Academy of Arts and Sciences.^[4] In 1966, the minor planet9686 Keesom was named after him.

• Timeline of low-temperature technology

• Albert van Helden,Willem Hendrik Keesom 1876 – 1956, In: K. van Berkel, A. van Helden and L. Palm ed., A History of Science in the Netherlands. Survey, Themes and Reference (Leiden: Brill, 1999) 498–500.
• Scientists of the Dutch School:Willem Hendrik Keesom @ Royal Netherlands Academy of Arts and Sciences.
• P.H. van Laer,Keesom, Wilhelmus Hendrikus (1876-1956), in Biografisch Woordenboek van Nederland.

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