Monday, October 24, 2011

Felix Bloch

Felix Bloch was born on October 23, 1905 in Zurich, Switzerland.  His father, Gustav Bloch was a wholesale grain seller in Zurich.  He entered public elementary school at age 6 and initially had trouble in school because he spoke Swiss German with an accent different than those of his peers.  In 1918 he began attending gymnasium run by the canton of Zurich.  Young Bloch excelled in mathematics and science and in 1924 he passed his "matura" an exam that allowed him to go on to an institution of higher learning.  Initially planning to study engineering he entered Federal Institute of Technology in Zurich.  After a year he changed his mind and began to study physics and continued at the same institution, graduating in 1927.

After graduating he went to the University of Lepzig, where he studied under Werner Heisenberg, completing his Ph.D. in 1928.  His doctoral thesis introduced the concept of Bloch waves to explain the behavior of electrons in crystals, developing the theory of metallic conduction.  After finishing his doctorate he took a tour of the various centers of experimental physics in Europe working for Wolfgang Pauli at the University of Zurich, Niels Bohr in Copenhagen, and Enrico Fermi in Rome, before returning to the University of Lepzig as a lecturer in physics.  In 1933, soon after Hitler came to power in Germany, he emigrated to the United States, taking a position at Stanford University in Palo Alto, California.  Bloch became Stanford's first professor of theoretical physics in 1939.  During World War II he worked on nuclear power at Los Alamos Nuclear Laboratory and on ways to interfere with radar at Harvard University.  After the war he returned to Stanford.

Bloch is most famous for his work developing the theory of nuclear induction and magnetic resonance.  Atoms that have an uneven number of protons and/or neutrons have an intrinsic magnetic moment and angular momentum.  This is called spin.  When placed into a magnetic field nuclei will emit electromagnetic radiation, as their spin lines up with the magnetic field.   The frequency of this emission depends on the strength of the magnetic field and the isotope.  By measuring these emissions it is possible to determine the chemical structure in which the atom resides.  This technique is used by chemists to determine the structure of compounds and it is used in medical imaging and is called magnetic resonance imaging, or MRI (the name was changed to remove the word "nuclear").  For his discovery of nuclear magnetic resonance Bloch won the Nobel Prize for physics in 1952, which he shared with Edward Mills Purcell who developed the theory simultaneously.

In 1952 Bloch became the first director of CERN, the European Organization for Nuclear Research, and he formulated its early policies regarding atomic research.  Because as director he had little time for research he returned to Stanford a year later.  In 1965 he served as president of the American Physical Society.

Bloch died on September 10, 1983.


Hofstader, Richard; "Felix Bloch"; Physics Today (1984)37:115-116

Hofstader, Richard; "Felix Bloch: 1905-1983" in Biographical Memoirs Vol. 64; National Academy Press; 1994

Felix Bloch Nobel Biography

Felix Bloch Wikipedia Entry

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