Photo from the Nobel Foundation archive.
Norman F. Ramsey
Born: 27 August 1915, Washington, DC, USA
Died: 4 November 2011, Wayland, MA, USA
Affiliation at the time of the award: Harvard University, Cambridge, MA, USA
Prize motivation: "for the invention of the separated oscillatory fields method and its use in the hydrogen maser and other atomic clocks."
Prize share: 1/2
According to the laws of quantum mechanics, atoms can have only fixed energy levels. When there are transitions among different energy levels, electromagnetic radiation with certain frequencies is emitted or absorbed. After Isaac Isidor Rabi developed a method to determine these frequencies by passing a beam of atoms through a magnetic and electromagnetic field, Norman Ramsey refined the method in 1949 through the interference of two electromagnetic fields. This improved precision and became the basis for the atomic clock.