(August 27, 1915 – November 4, 2011)
Biography
Ramsey was born in Washington, DC on August 27, 1915 to Minna Bauer Ramsey, a mathematics teacher, and Norman Foster Ramsey, a West Point graduate and an officer in the Army Ordinance Corps. He earned his B.A. in Mathematics from Columbia University in 1935. On his graduation, Columbia awarded him a Kellett Fellowship to Cambridge University where he earned a second bachelors degree, this time in physics. His tutor at Cambridge was Maurice Goldhaber, who stimulated Ramsey's interest in molecular beams and in doing research for a Ph.D with I.I. Rabi at Columbia. He received his Ph.D. in physics from Columbia University in 1940.[3] In 1940, he married Elinor Jameson of Brooklyn, New York and moved to the University of Illinois with the expectation of spending the rest of his life there. World War II was, however, raging in Europe, and Ramsey was recruited to the MIT Radiation Lab where he spent the next two years heading up the group developing 3 cm wavelength radar. After a stint in Washington, D.C. as a radar consultant to the Secretary of War, he went, in 1943, to Los Alamos to work on the Manhattan Project. At the end of the war, Ramsey returned to Columbia University as a professor and research scientist. With Rabi, he helped establish the Brookhaven National Laboratory on Long Island, NY, where he became the first head of the Physics Department. In 1947, he moved to Harvard University.,[1] where he taught for the next 40 years, except for visiting professorships a Middlebury College, Oxford University, Mt. Holyoke College and the University of Virginia. His first wife, Elinor, died in 1983, after which he married Ellie Welch of Brookline, Massachusetts. Ramsey died on November 4, 2011, survived by his second wife, seven children and six grandchildren.Research
Ramsey's research in the immediate post-war years looked at measuring fundamental properties of atoms and molecules by use of molecular beams. On moving to Harvard, his objective was to carry out accurate molecular beam magnetic resonance experiments, based on the techniques developed by Rabi. However, the accuracy of the measurements depended on the uniformity of the magnetic field, and Ramsey found that it was difficult to create sufficiently uniform magnetic fields. He developed the separated oscillatory field method in 1949 as a means of achieving the accuracy he wanted.[3]Ramsey and Daniel Kleppner developed the atomic hydrogen maser, looking to increase the accuracy with which the hyperfine separations of atomic hydrogen, deuterium and tritium could be measured, as well as to investigate how much the hyperfine structure was affected by external magnetic and electric fields. He also participated in developing an extremely stable clock based on a hydrogen maser. Since 1967, the second has been defined based on a hyperfine transition of a cesium atom; the atomic clock which is used to set this standard is an application of Ramsey's work,[4] and Ramsey was awarded the Nobel prize in physics in 1989 "for the invention of the separated oscillatory fields method and its use in the hydrogen maser and other atomic clocks".[5] The Prize was shared with Hans G. Dehmelt and Wolfgang Paul.
In collaboration with the Institut Laue–Langevin, Ramsey also worked on applying similar methods to beams of neutrons, measuring the neutron magnetic moment and finding a limit to its electric dipole moment.[3]
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