Felix Bloch

Felix Bloch
Bloch in 1961
Born	(1905-10-23)23 October 1905 Zürich, Switzerland
Died	10 September 1983(1983-09-10) (aged 77) Zürich, Switzerland
Nationality	Swiss
Citizenship	Swiss American
Alma mater	ETH Zürich University of Leipzig
Known for	NMR spectroscopy Magnon Radiative Auger effect Spin wave Tight binding Inverse cyclotron converter Bloch equations Bloch oscillation Bloch wave Bloch wall Bloch's theorem Bloch sphere Bloch spectrum Bloch T3/2 law Bloch–Grüneisen temperature Bloch–Nordsieck theorem Bloch–Siegert shift Bethe–Bloch formula
Awards	Nobel Prize for Physics (1952) Fritz London Memorial Lecture (1959) Guggenheim Fellowship (1959) Pour le Mérite for Sciences and Arts (1979)
Scientific career
Fields	Physics
Institutions	Stanford University University of California, Berkeley
Doctoral advisor	Werner Heisenberg
Doctoral students	Carson D. Jeffries

Felix Bloch (/blɒk/; German: [blɔx]; 23 October 1905 – 10 September 1983) was a Swiss-American physicist and Nobel physics laureate who worked mainly in the U.S.^[1] He and Edward Mills Purcell were awarded the 1952 Nobel Prize for Physics for "their development of new ways and methods for nuclear magnetic precision measurements."^[2] In 1954–1955, he served for one year as the first director-general of CERN. Felix Bloch made fundamental theoretical contributions to the understanding of ferromagnetism and electron behavior in crystal lattices. He is also considered one of the developers of nuclear magnetic resonance.

Bloch was born in Zürich, Switzerland to Jewish^[3] parents Gustav and Agnes Bloch. Gustav Bloch, his father, was financially unable to attend University and worked as a wholesale grain dealer in Zürich.^[4] Gustav moved to Zürich from Moravia in 1890 to become a Swiss citizen. Their first child was a girl born in 1902 while Felix was born three years later.^[4]

Bloch entered public elementary school at the age of six and is said to have been teased, in part because he "spoke Swiss German with a somewhat different accent than most members of the class".^[4] He received support from his older sister during much of this time, but she died at the age of twelve, devastating Felix, who is said to have lived a "depressed and isolated life" in the following years.^[4] Bloch learned to play the piano by the age of eight and was drawn to arithmetic for its "clarity and beauty".^[4] Bloch graduated from elementary school at twelve and enrolled in the Cantonal Gymnasium in Zürich for secondary school in 1918. He was placed on a six-year curriculum here to prepare him for University. He continued his curriculum through 1924, even through his study of engineering and physics in other schools, though it was limited to mathematics and languages after the first three years. After these first three years at the Gymnasium, at age fifteen Bloch began to study at the Eidgenössische Technische Hochschule (ETHZ), also in Zürich. Although he initially studied engineering he soon changed to physics. During this time he attended lectures and seminars given by Peter Debye and Hermann Weyl at ETH Zürich and Erwin Schrödinger at the neighboring University of Zürich. A fellow student in these seminars was John von Neumann.

Bloch graduated in 1927, and was encouraged by Debye to go to Leipzig to study with Werner Heisenberg.^[5] Bloch became Heisenberg's first graduate student, and gained his doctorate in 1928.^[5] His doctoral thesis established the quantum theory of solids, using waves to describe electrons in periodic lattices.

On March 14, 1940, Bloch married Lore Clara Misch (1911–1996), a fellow physicist working on X-ray crystallography, whom he had met at an American Physical Society meeting.^[6] They had four children, twins George Jacob Bloch and Daniel Arthur Bloch (born January 15, 1941), son Frank Samuel Bloch (born January 16, 1945), and daughter Ruth Hedy Bloch (born September 15, 1949).^[5][7]

Bloch remained in European academia, working on superconductivity with Wolfgang Pauli in Zürich; with Hans Kramers and Adriaan Fokker in Holland; with Heisenberg on ferromagnetism, where he developed a description of boundaries between magnetic domains, now known as "Bloch walls", and theoretically proposed a concept of spin waves, excitations of magnetic structure; with Niels Bohr in Copenhagen, where he worked on a theoretical description of the stopping of charged particles traveling through matter; and with Enrico Fermi in Rome.^[5] In 1932, Bloch returned to Leipzig to assume a position as "Privatdozent" (lecturer).^[5] In 1933, immediately after Hitler came to power, he left Germany because he was Jewish, returning to Zürich, before traveling to Paris to lecture at the Institut Henri Poincaré.^[8]

In 1934, the chairman of Stanford Physics invited Bloch to join the faculty.^[5] Bloch accepted the offer and emigrated to the United States. In the fall of 1938, Bloch began working with the 37 inch cyclotron at the University of California, Berkeley to determine the magnetic moment of the neutron. Bloch went on to become the first professor for theoretical physics at Stanford. In 1939, he became a naturalized citizen of the United States.

During WWII, Bloch briefly worked on the atomic bomb project at Los Alamos. Disliking the military atmosphere of the laboratory and uninterested in the theoretical work there, Bloch left to join the radar project at Harvard University.^[9]

After the war, he concentrated on investigations into nuclear induction and nuclear magnetic resonance, which are the underlying principles of MRI.^[10][11][12] In 1946 he proposed the Bloch equations which determine the time evolution of nuclear magnetization. He was elected to the United States National Academy of Sciences in 1948.^[13] Along with Edward Purcell, Bloch was awarded the 1952 Nobel Prize in Physics for his work on nuclear magnetic induction.

When CERN was being set up in the early 1950s, its founders were searching for someone of stature and international prestige to head the fledgling international laboratory, and in 1954 Professor Bloch became CERN's first director-general,^[14] at the time when construction was getting under way on the present Meyrin site and plans for the first machines were being drawn up. After leaving CERN, he returned to Stanford University, where he in 1961 was made Max Stein Professor of Physics.

In 1964, he was elected a foreign member of the Royal Netherlands Academy of Arts and Sciences.^[15] He was also a member of the American Academy of Arts and Sciences and the American Philosophical Society.^[16][17]

Bloch died in Zürich in 1983.^[6]

• List of Jewish Nobel laureates
• List of things named after Felix Bloch

• "Nobel Prize for Physics, 1952". Nature. 170 (4335): 911–912. 1952. Bibcode:1952Natur.170R.911.. doi:10.1038/170911b0. S2CID 4205574.
• "Deputy Director-General: Prof. E. Amaldi". Nature. 174 (4434): 774–775. 1954. Bibcode:1954Natur.174R.774.. doi:10.1038/174774c0. S2CID 4263821.
• McGraw-Hill Modern Men of Science. Vol. 1. McGraw-Hill. 1966. pp. 45–46. ISBN 978-0-07-045217-6.
• National Cyclopaedia of American Biography. Vol. 61. James T. White & Co. 1984. pp. 310–312. ISBN 0-88371-040-4.

• Bloch, F.; Staub, H. "Fission Spectrum", Los Alamos National Laboratory (LANL) (through predecessor agency Los Alamos Scientific Lab), United States Department of Energy (through predecessor agency the US Atomic Energy Commission), (August 18, 1943).

• Media related to Felix Bloch at Wikimedia Commons

Wikiquote has quotations related to Felix Bloch.

• Felix Bloch on Nobelprize.org
• Oral History interview transcript with Felix Bloch on 14 May 1964, American Institute of Physics, Niels Bohr Library and Archives - interview conducted by Thomas S. Kuhn in Palo Alto, California
• Oral History interview transcript with Felix Bloch on 15 August 1968, American Institute of Physics, Niels Bohr Library and Archives - interview conducted by Charles Weiner at Stanford University
• Oral History interview transcript with Felix Bloch 15 December 1981, American Institute of Physics, Niels Bohr Library and Archives - interview conducted by Lillian Hoddeson at Stanford University
• Felix Bloch Papers, 1931–1987 (33 linear ft.) are housed in the Department of Special Collections and University Archives at Stanford University Libraries
• National Academy of Sciences Biographical Memoir
• Felix Bloch Papers