- Person
- Otto Stern
- Lived
- 1888–1969
- Field
- Experimental physics
- From
- German-American
The story
Isidor Isaac Rabi was born in 1898 in Rymanów, in what was then Austria-Hungary, and grew up on New York's Lower East Side. After a doctorate at Columbia University he went to Europe in 1927 to learn the new quantum physics. In Copenhagen, Niels Bohr arranged for him and Yoshio Nishina to work with the theorist Wolfgang Pauli at the University of Hamburg.
There Rabi found Otto Stern's molecular-beam laboratory, then one of the leading centres of physics in the world, and was drawn into its experiments through Stern's two English-speaking fellows, Ronald Fraser and John Bradshaw Taylor. Stern's group used uneven magnetic fields that were hard to control and measure. Rabi came up with a cleverer arrangement, using a uniform field with the beam entering at a glancing angle, so that atoms would be deflected like light through a prism. He explained the idea to Stern, who invited him to do the experiment, and with Taylor's help it worked. Stern insisted that Rabi publish first in Nature under his own name, so that no one would think it was Stern's work. The letter appeared in February 1929. Rabi later said that from Stern and Pauli he learned what physics should be.
Back at Columbia, Rabi built on Stern's methods. In 1937 he and his students devised the molecular-beam magnetic resonance method, using a radio-frequency field to flip the orientation of atomic nuclei between two magnets. It measured nuclear magnetic properties with great precision and won him the 1944 Nobel Prize in Physics. In 1945 he proposed using atomic resonance to build clocks, and such atomic clocks were soon made. Several of his students and colleagues, including Polykarp Kusch, Norman Ramsey and Charles Townes, went on to win Nobel Prizes of their own.
Rabi's method led to nuclear magnetic resonance spectroscopy and to magnetic resonance imaging. Near the end of his life, Rabi himself was examined in an MRI scanner and remarked that he had never thought his work would come to this.
Its roots run back to Stern's Hamburg laboratory, where a visiting American learned to work with beams of atoms and was encouraged to try his own ideas. The 2011 history of Stern's career notes that about 20 Nobel Prizes were eventually awarded for work based on the molecular-beam method.
Why it matters
Through Rabi, Stern's methods led to MRI scanners that help diagnose illness without radiation, and to atomic clocks that keep GPS and global communications in time.
About Otto Stern
Physicist whose molecular-beam method proved space quantisation in the Stern–Gerlach experiment and measured the proton’s magnetic moment; Nobel Prize in Physics 1943.
More about Otto Stern
- Otto Stern showed whole atoms behave like wavesAround 1930 Otto Stern's Hamburg laboratory diffracted beams of helium atoms and hydrogen molecules off crystals, proving that entire atoms, not just electrons, travel as waves.
- Otto Stern proved atoms obey quantum rules in 1922In February 1922 the Stern–Gerlach experiment split a beam of silver atoms cleanly in two, the first direct proof that quantum rules govern how atoms behave in a magnetic field.
- Otto Stern made molecular beams a precision toolIn 1920 Otto Stern measured the speed of silver atoms in a vacuum, turning molecular beams, first used by Louis Dunoyer in 1911, into a precise tool for studying single atoms.
- Otto Stern found the proton is not a simple particleIn 1933 Otto Stern, Otto Frisch and Immanuel Estermann measured the proton's magnetism and found it unexpectedly large, the first sign that the proton has inner structure.
Sources
- Isidor Isaac Rabi Wikipedia
- Otto Stern Wikipedia
- Otto Stern (1888–1969): The founding father of experimental atomic physics Annalen der Physik (arXiv)
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