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Felix Bloch

Felix Bloch

Felix Bloch was born into a Jewish family in Zurich, Switzerland, on 23rd October, 1905. He studied mathematics, engineering and physics in Zurich before moving to Germany to study under Werner Heisenberg at the University of Leipzig..

In 1928 Bloch published his doctoral thesis which became the basis for the quantum theory of electrical conduction. Over the next five years he worked with Niels Bohr and Enrico Fermi and other leading scientists working in this field.

When Adolf Hitler gained power in 1933 Bloch emigrated to the United States and worked at Stanford University where he continued his research into neutrons.

In 1943 Bloch joined the Manhattan Project. In the United States. Over the next two years he worked with Robert Oppenheimer, Edward Teller, Otto Frisch, Felix Bloch, Enrico Fermi, David Bohm, James Chadwick, James Franck, Emilio Segre, Niels Bohr, Eugene Wigner, Leo Szilard and Klaus Fuchs in developing the atom bombs dropped on Hiroshima and Nagasaki.

After the war Bloch returned to Stanford University where he continued his research and in 1953 he won the Nobel Prize for his work on nuclear magnetic resonance. The following year Bloch was appointed the first Director General of CERN in Geneva. Felix Bloch died in 1983.


Felix Bloch

Felix Bloch was born in Zürich, Switzerland. He was educated there and at the Eidgenössische Technische Hochschule, also in Zürich. Initially studying engineering he soon changed to physics. Graduating in 1927, he continued his physics studies at the University of Leipzig, gaining his doctorate in 1928. He remained in German academia, studying with Heisenberg, Wolfgang Pauli, Niels Bohr and Enrico Fermi.

In 1933, he left Germany, emigrating to work at Stanford University in 1934. He was naturalised in 1939.

During World War II, he worked on atomic energy at Los Alamos National Laboratory, before resigning to join the radar project at Harvard University. After the war, Bloch concentrated on investigations into nuclear induction and nuclear magnetic resonance, which are the underlying principles of MRI. He and Edward Mills Purcell were awarded the 1952 Nobel Prize in Physics for “their development of new methods for nuclear magnetic precision measurements.”

In 1954�, Bloch served for one unsatisfactory year as the first Director-General of CERN. In 1961, he was made Max Stein Professor of Physics at Stanford University.

Sources: Wikipedia. This article is available under the terms of the GNU Free Documentation License

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Contents

Early life, education, and family

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

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". Β] 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. Β] Bloch learned to play the piano by the age of eight and was drawn to arithmetic for its "clarity and beauty". Β] 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. Γ] Bloch became Heisenberg's first graduate student, and gained his doctorate in 1928. Γ] 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. Δ] 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 Alexander (born September 15, 1949). Γ] Ε]

Career

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. Γ] In 1932, Bloch returned to Leipzig to assume a position as "Privatdozent" (lecturer). Γ] 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. Ζ]

In 1934, the chairman of Stanford Physics invited Bloch to join the faculty. Γ] 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 at 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 World War II , 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. Η]

After the war, he concentrated on investigations into nuclear induction and nuclear magnetic resonance, which are the underlying principles of MRI. ⎖] ⎗] ⎘] In 1946 he proposed the Bloch equations which determine the time evolution of nuclear magnetization. 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, ⎙] 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. ⎚]


Felix Bloch

Physicist Felix Bloch developed a non-destructive technique for precisely observing and measuring the magnetic properties of nuclear particles.

He called his technique “nuclear induction,” but nuclear magnetic resonance (NMR) soon became the preferred term for the method, which was a notable advance upon an earlier technique developed by Isidor Rabi. Bloch received half of the Nobel Prize in Physics in 1952 for this work, sharing the award with Edward Purcell, who independently developed a similar method of achieving and detecting nuclear magnetic resonance at about the same time. NMR is the basis of an important medical imaging technique, magnetic resonance imaging (MRI).

A native of Zürich, Switzerland, Bloch was born on October 23, 1905. His parents were Gustav Bloch, a merchant, and Agnes Mayer. Because of their son’s apparent skill in mathematics and science, they encouraged him to pursue an engineering career. However, after briefly studying the subject at the Swiss Federal Institute of Technology, he decided to follow a different path. Bloch began studying physics and had the opportunity of learning from many prominent researchers in the field, including Erwin Schrödinger, Peter Debye, and Paul Scherrer. Following his graduation in 1927, he entered the University of Leipzig for graduate studies. There he was taught by yet another leading physicist of the day, Werner Heisenberg. After just one year, Bloch received his doctorate. His dissertation applied quantum theory to the study of crystals and theoretically addressed electrical conduction.

Bloch held a number of research fellowships before accepting an academic post at Leipzig. He left the position when the climate in Germany became unfavorable for him and other Jews due to the rise of Hitler. In 1934 he settled in the United States, where he joined the academic staff at Stanford University. He remained there most of his career. His work began to encompass the experimental, in addition to the theoretical, side of physics. Some of his early areas of interest included ferromagnetism, wave functions of electrons in solids, and the relationship between temperature and conduction. But James Chadwick’s discovery of the neutron in 1932 sparked Bloch’s curiosity. Much of his initial research at Stanford focused on the neutron.

Physicist Otto Stern experimentally demonstrated in 1933 that the neutron, despite its lack of charge, has a magnetic moment. Bloch decided he would attempt to determine how it was possible, since the magnetic moment of the electron had been explained as originating from its charge. But first he sought direct proof of what Stern’s experiments only indirectly indicated. In 1936, Bloch proposed such proof could be found from observations of neutron scattering in samples of iron, and the following year researchers successfully employed the method he suggested to obtain the evidence Bloch sought. A few years later, Bloch himself, in conjunction with Luis Alvarez, carried out experiments with the cyclotron at the University of California at Berkeley to measure the neutron’s magnetic moment. That same year, 1939, Bloch gained American citizenship.

In 1940, Bloch wed Lore Misch, a physicist who had also emigrated from Germany. The couple later had four children. Shortly after his marriage, Bloch’s work at Stanford temporarily came to a halt due to the U.S. involvement in World War II. He took a leave of absence from his academic post to work on the Manhattan Project in Los Alamos, New Mexico, until 1944. He also became involved in developing methods of counteracting radar at the Harvard University Radio Research Laboratory.

His work at Harvard aided Bloch when he returned to Stanford after the war. In his study of nuclear magnetic moments, Bloch was inspired to use radio frequencies to control a weak magnetic field used to incite nuclear excitation in a sample, which also in Bloch’s set-up was exposed to a much stronger magnetic field. Once excited, signals produced by the spinning of nuclei could be detected with a receiving apparatus. The signals enabled Bloch to assess nuclear magnetic moments with a considerable degree of precision. Bloch also found that atoms in a sample only absorb energy and vibrate at a specific frequency, so his technique led to a variety of discoveries about materials on the atomic and molecular levels.

In 1946, Bloch’s achievement was heralded in two research papers published in Physical Review. He and the rest of the world soon found that the same basic discovery had been made by American physicist Edward Purcell. When the Nobel Foundation recognized the importance of the new means of measuring nuclear magnetic moments, both Bloch and Purcell were honored. In the following years, Bloch continued to carry out notable scientific research, much of it extending from his work with NMR. He also explored other topics, including superconductivity.

Bloch retired from Stanford in the early 1970s and returned to his hometown in Switzerland. He died there on September 10, 1983 from a heart attack. Over the course of his life, he received many honors and awards in addition to the Nobel Prize. Bloch became a member of the National Academy of Sciences in 1948, was chosen to be the first director general of the European Commission for Nuclear Research (CERN) in 1954, and became president of the American Physical Society in 1965. Also, several universities granted him honorary degrees and a number of prestigious scientific societies in other countries granted him honorary fellowships.


Felix Bloch and the Nuclear Magnetic Resonance Method

On October 23 , 1905 , Swiss -born American physicist Felix Bloch was born. He is best known for his investigations into nuclear induction and nuclear magnetic resonance , which are the underlying principles of MRI . He was awarded the 1952 Nobel Prize in Physics for developing the nuclear magnetic resonance ( NMR ) method of measuring the magnetic field of atomic nuclei .

Felix Bloch was educated at the Eidgenössische Technische Hochschule in Zurich , starting out in engineering. Later on, he increased his interest in physics and attended the lectures of Peter Debye and Hermann Weyl at ETH Zürich and Erwin Schrödinger at the University of Zurich .

One of his fellow students was also John von Neumann . Bloch graduated in 1927 and continued his studies at the University of Leipzig . There, he met and studied with Werner Heisenberg , he received his Ph.D . in 1928 . His doctoral thesis established the quantum theory of solids, using Bloch waves to describe the electrons .

Bloch remained in Europe in the following period. He studied with Wolfgang Pauli in Zürich , Niels Bohr in Copenhagen and Enrico Fermi in Rome . He was then appointed privatdozent in Leipzig and had to leave Germany due to the rise of the Nazi party. Bloch continued his career at Stanford University and later Berkeley . He became a citizen of the United States and worked on nuclear power at Los Alamos National Laboratory during World War II before resigning to join the radar project at Harvard University . Felix Bloch focused on his research on nuclear magnetic resonance and nuclear induction. Nuclear magnetic resonance was first described and measured in molecular beams by Isidor Rabi around 1938 . In 1944 , Rabi was awarded the Nobel Prize in physics for this work on the topic. About two years later, Felix Bloch and Edward Mills Purcell expanded the technique for use on liquids and solids, for which they shared the Nobel Prize in Physics in 1952 . The three scientists, Rabi , Bloch , and Purcell observed that magnetic nuclei could absorb RF energy when placed in a magnetic field and when the RF was of a frequency specific to the identity of the nuclei. When this absorption occurs, the nucleus is described in resonance. Different atomic nuclei within a molecule resonate at different frequencies for the same magnetic field strength. The observation of such magnetic resonance frequencies of the nuclei present in a molecule allows any trained user to discover essential chemical and structural information about the molecule. The development of Nuclear Magnetic Resonance as a technique in analytical chemistry and biochemistry parallels the development of electromagnetic technology and advanced electronics and their introduction into civilian use.

At yovisto, you may be interested in a video lecture on MRI-Driven Turbulence – MRI-driven Turbulence with Resistivity by Professor Takayoshi Sano at Princeton.


Spatial encoding

In September 1971, Paul Lauterbur (see Figure 2) of the State University of New York at Stony Brook had the idea of applying magnetic field gradients in all three dimensions and a back-projection (= projection–reconstruction) technique to create NMR images. He published the first images of two tubes of water in March 1973 in the journal Nature. This was followed later in the year by the picture of a living animal, a clam, and in 1974 by the image of the thoracic cavity of a mouse. Lauterbur called his imaging method zeugmatography, a term which was later replaced by (N)MR imaging.

Figure 2. Paul C. Lauterbur (1929–2007).

Field gradients had been used before. They are an essential feature of the study of molecular diffusion in liquids by the spin-echo method developed by Erwin L. Hahn in 1950 his group at Berkeley used a gradient approach also to create a storage memory. In 1951, Roger Gabillard from Lille in France had imposed one-dimensional gradients on samples. Carr and Purcell described the use of gradients in the determination of diffusion in 1954.

However, Lauterbur’s idea revolutionised NMR because it opened the field to imaging. Many of today’s innovations were thought of and developed in his laboratory in the late 1970s and 1980s. When he presented his approach to NMR imaging at the International Society of Magnetic Resonance (ISMAR) meeting in January 1974 in Bombay, Raymond Andrew, William Moore and Waldo Hinshaw from the University of Nottingham, UK, were in the audience and took note. As a result, Hinshaw developed his own approach to MR imaging with their sensitive point method.

In April 1974, Lauterbur gave a talk at a conference in Raleigh, North Carolina. This conference was attended by Richard Ernst from Zurich, who realised that instead of Lauterbur’s back-projection one could use switched magnetic field gradients in the time domain. This led to the 1975 publication, NMR Fourier Zeugmatography by Anil Kumar, Dieter Welti and Richard Ernst, and to the basic reconstruction method for MR imaging today.

A second NMR group in Nottingham also got involved in MR imaging. Its leader, Peter Mansfield, worked on studies of solid periodic objects, such as crystals. At a Colloque Ampère conference in Cracow in September 1973, Mansfield and his collaborator Peter K. Grannell presented a one-dimensional interferogram to a resolution of better than 1 mm. This, however, cannot be considered an MR image. However, one year later, Alan Garroway and Mansfield filed a patent and published a paper on image formation by NMR. By 1975, Mansfield and Andrew A. Maudsley proposed a line technique, which, in 1977, led to the first image of in vivo human anatomy, a cross-section through a finger. In 1978, Mansfield presented his first image through the abdomen.

In 1977, Hinshaw, Paul Bottomley and Neil Holland succeeded with an image of the wrist. Human thoracic and abdominal images followed, and by 1978, Hugh Clow and Ian R. Young, working at the British company EMI, reported the first transverse NMR image through a human head. Two years later, William Moore and colleagues presented the first coronal and sagittal images through a human head.

In the research group of John Mallard at the University of Aberdeen, Jim Hutchison, Bill Edelstein and colleagues developed the spin-warp technique. They published a first image through the body of a mouse in 1974. Margaret Foster contributed much to this work.

Some of the pioneers had performed quite impressive research in the United States among them was Robert N. Muller (see Figure 3), who, in 1982, described off-resonance imaging, a technique known today as “magnetisation-transfer” imaging. Rinck et al. described, while at the State University of New York at Stony Brook, the first fluorine lung images.

Figure 3. Early magnetic resonance imaging experiment at Paul C. Lauterbur’s Laboratory in Stony Brook, NY, around 1981: left Peter A. Rinck, right Robert N. Muller.

Paul C. Lauterbur received the Nobel Prize in Medicine or Physiology in 2003 for the invention of magnetic resonance imaging. Peter Mansfield shared the Nobel Prize for his further development of MRI.

In the 1980s, Continental Europe started to contribute intensively to MR imaging. Rapid imaging originated in European laboratories. Jürgen Hennig, together with A. Nauerth and Hartmut Friedburg, from the University of Freiburg introduced RARE (rapid acquisition with relaxation enhancement) imaging in 1986. This technique is probably better known under the commercial names of fast or turbo spin-echo.

At about the same time, FLASH (fast low angle shot) appeared, opening the way to similar gradient-echo sequences. This sequence was developed at the Max-Planck-Institute, Göttingen, by Axel Haase, Jens Frahm, Dieter Matthaei, Wolfgang Hänicke and Dietmar K. Merboldt. FLASH was very rapidly adopted commercially. Hennig’s RARE was slower, and echo-planar imaging (EPI)—for technical reasons—took even more time. Echo-planar imaging had been proposed by Mansfield’s group in 1977, and the first crude images were shown by Mansfield and Ian Pykett in the same year. Roger Ordidge presented the first movie in 1981. Its breakthrough came with manifold improvements in many aspects of the associated methodology and instrumentation—from gradient power supply and gradient coil design to pulse sequence development, presented by Pykett and Rzedzian in 1987.


Felix Bloch Papers, 1931-1987

The Bloch papers document Felix Bloch's role in twentieth century physics as a scientist, teacher and administrator. The collection includes correspondence, grant proposals, lecture notes, minutes and accompanying documentation regarding departmental, university and national committees, research notebooks, grants, patents, and designs files regarding organizations in which Bloch played an active role publications (predominantly reprints) by Bloch and photographs. While the collection includes some correspondence from the 1930's, the bulk of the collection dates from the period of his research in nuclear induction (1946-52) to 1983. Of special note is extensive correspondence with Stanford colleagues during his tenure as Director of CERN regarding the growth of Big Science and his reservations about the influence of large federally funded projects at the University, particularly the creation of the Stanford Linear Accelerator Center. Also well documented is the growth of the physics Department during the 1950s through 1980s and Bloch's presidency of the American Physical Society. Series III contains research notes and notebooks, grant proposals and reports, contracts, patents, and apparatus designs. All the material contained in these boxes relates to Bloch's role as a research scientist. The patents on Bloch's inventions included here come from the United States, Canada, France, Switzerland, and Great Britain. Primarily for gyromagnetic devices, these patents contain some detailed design specifications.


Felix Bloch

Felix Bloch was a Swiss physicist and the winner of the 1952 Nobel Prize.

Bloch was born in 1905 in Zurich, Switzerland. He attended the Federal Institute of Technology in Zurich and went on to study with Werner Heisenberg at the University of Leipzig. During his time in Germany, Bloch also worked with Niels Bohr and Enrico Fermi.

After the rise of Hitler in 1933, Bloch moved to the United States where he accepted a teaching position at Stanford University. Together with Luis Alvarez, Bloch used the 37-inch Berkeley cyclotron to collect some of the first measurements of the neutron magnetic moment. In 1943, Bloch went to Los Alamos where he worked on theoretical problems with Hans Bethe and on implosion with Seth Neddermeyer. Unhappy with the military atmosphere of Los Alamos, however, Bloch soon left for Harvard University, where he researched radar for the duration of the war.

In 1952, Bloch shared the Nobel Prize in Physics with Edward Purcell for his work on nuclear magnetic resonance. The two scientists received the prize “for their development of new methods for nuclear magnetic precision measurements and discoveries in connection therewith.” Bloch would go on to be named the first Director-General of CERN, the European Organization for Nuclear Research.


History

Felix Bloch Erben was founded in 1849 by Waldemar Bloch , father of the later eponymous Felix Bloch , who joined the "Theater Association Office" C. Klose in Berlin that year and took over this together with the affiliated "Theater Association newspaper" a short time later. At that time, the term “theater association office” was understood to mean an agency that published both dramatic and musical works and also acted as an agency for actors. The "Theater Association Newspaper", which Waldemar Bloch took over in 1849, quickly developed into one of the most important newsletters in the German-speaking theater world. In 1862 it was given the name "charivari", which is still used today for the publishing magazine .

After Waldemar Bloch's death, Felix Bloch took over the company, after Felix Bloch's death in 1887 his widow, and soon afterwards Adolf Sliwinski (1858–1916), who had married Felix Bloch's widow. This was followed by Ernst Bloch (1878-1923). After his death, his widow and daughter Lotte Volkmer (1915-2014) inherited the publishing house, later it was run by Fritz Wreede .


Biography of Felix Bloch

A Swiss-born American physicist who shared (with E.M. Purcell) the Nobel Prize for Physics in 1952 for developing the nuclear magnetic resonance method of measuring the magnetic field of atomic nuclei, Felix Bloch was born on 23 October 1905 in Zürich, Switzerland to Jewish parents Gustav and Agnes Bloch.

Bloch is considered one of the founders of solid-state physics. He made particularly significant contributions to the quantum theory of metals and solids, he worked on the magnetic scattering of neutrons and, together with Luis Alvarez, he experimentally measured the magnetic moment of the neutron. His discovery of nuclear magnetic resonance won him the Nobel Prize in Physics for 1952, which he shared with Edward Mills Purcell.

After passing secondary school, Bloch studied under the guidance of several imminent scientists of his time. He became an accomplished physicist who witnessed the emergence of modern quantum theory and explored its application on the conductivity of metals and ferromagnetism. All through his academic and research career, he contributed immensely to solid-state physics several theorems and laws have been named after him. He is remembered for the development of nuclear magnetic resonance techniques, which allowed highly precise measurements of magnetism of atomic nuclei. It went on to become an influential tool in both physics and chemistry, to analyze large molecules. Apart from Physics, he was interested in music, nature, literature, mountain climbing, and skiing. He had a great wit and was full of ironic humor. Gifted with an analytical bent of mind, he liked to get to the bottom of any problem and find a solution.

Childhood, Family and Educational Life

A Swiss-born American physicist, Felix Bloch was born on October 23, 1905, in Zurich, Switzerland to Jewish parents Gustav Bloch, a wholesale grain dealer, and Agnes Bloch. Both parents were Jews. His father moved to Zürich in 1890 to take a position in his uncle’s business and became a Swiss citizen. Bloch had an elder sister who died at the age of twelve. At the age of six, he joined a public primary school. However, with no encouragement from his teachers, he found it a very difficult place. He also took music lessons and was able to play the piano at the age of eight.

Bloch was educated at the Cantonal Gymnasium in Zürich and at the Eidgenössische Technische Hochschule (ETHZ), also in Zürich. Initially studying 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. Bloch became Heisenberg’s first graduate student and gained his doctorate in 1928. His doctoral thesis established the quantum theory of solids, using Bloch waves to describe electrons in periodic lattices.

Personal Life

On March 14, 1940, Felix 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. 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 Alexander (born September 15, 1949).

Bloch was a witty man and admired truthfulness, wisdom, innovation, and compassion. A man of strong principles and opinions, he disliked arrogance. He had an honest appreciation of the contributions he made. Although he was a friendly person, he would sometimes prefer isolation. He would take long walks alone when thinking about a difficult problem. At home, he possessed very few physics books and journals. He liked to add a very personal perspective to his work.

Career and Works

Felix Bloch developed an interest in theoretical physics. In 1927, he studied with Werner Heisenberg at the University of Leipzig and received his doctorate degree the next year. He wrote his thesis on ‘The Quantum Mechanics of Electrons in Crystal Lattices’ and calculated the specific heat and electrical resistance of metals in his paper. Bloch became Heisenberg’s first graduate student and gained his doctorate in 1928.

Bloch’s doctoral dissertation (University of Leipzig, 1928) promulgated a quantum theory of solids that provided the basis for understanding electrical conduction. Bloch taught at the University of Leipzig until 1933 when Adolf Hitler came to power he emigrated to the United States and was naturalized in 1939. After joining the faculty of Stanford University, Palo Alto, Calif., in 1934, he proposed a method for splitting a beam of neutrons into two components that corresponded to the two possible orientations of a neutron in a magnetic field. In 1939, using this method, he and Luis Alvarez (winner of the Nobel Prize for Physics in 1968) measured the magnetic moment of the neutron (a property of its magnetic field). Bloch worked on atomic energy at Los Alamos, N.M., and radar countermeasures at Harvard University during World War II.

In 1932, Felix Bloch returned to Leipzig to assume a position as “Privatdozent” (lecturer). 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. In 1934, the chairman of Stanford Physics invited Bloch to join the faculty. Bloch accepted the offer and emigrated to the United States.

In the summer of 1935, Bloch combined a trip he took to Switzerland with a trip to Copenhagen. Bohr thought that Bloch’s experience with problems of ferromagnetism would be useful for thinking about the physics of the newly discovered neutron. Since the magnetic moment of neutron had already been discovered, Bloch started considering the possibilities of polarized neutrons in ferromagnetic materials. In a letter to the Physical Review Bloch submitted in 1936, he outlined his theory of magnetic scattering of neutrons. It was also shown that the scattering could lead to a beam of polarized neutrons and how temperature variations of the ferromagnet could be used to separate the atomic scattering from the nuclear scattering.

In the fall of 1938, Bloch began working with the 37-inch cyclotron at the University of California at 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 World War II, Bloch worked on nuclear power at Los Alamos National Laboratory and later joined the radar project at Harvard University. After the war, he focused on nuclear induction and nuclear magnetic resonance, which became the fundamental principles of MRI.

Bloch returned to Stanford in 1945 to develop, with physicists W.W. Hansen and M.E. Packard, the principle of nuclear magnetic resonance, which helped establish the relationship between nuclear magnetic fields and the crystalline and magnetic properties of various materials. It later became useful in determining the composition and structure of molecules. Nuclear magnetic resonance techniques have become increasingly important in diagnostic medicine.

In 1946, Bloch proposed the ‘Bloch Equations’ which determined the time evolution of nuclear magnetization. Bloch and Purcell shared the Nobel Prize in Physics in 1952 for the development of new methods for the exact measurement of nuclear magnetism and for the discoveries made in the development of these methods. This was Stanford’s first Nobel Prize.

In 1954, Bloch became CERN’s first Director-General. However, not much interested in administrative work, he left the organization after a year. Nevertheless, he left back a huge and positive influence. He returned to Stanford University, where in 1961 he was made Max Stein Professor of Physics. In 1965, Bloch became President of the American Physical Society and attempted to develop a simplified physical theory of superconductivity.

Bloch was also a member of the National Academy of Sciences, the American Academy of Arts and Sciences, the American Philosophical Society, and the German honor society known as Pour le Mérite. He was appointed an honorary member of the Swiss Physical Society and received honorary degrees from Grenoble University, Oxford University, the University of Jerusalem, and the University of Zürich. He was, also, a member of the American Professors for Peace in the Middle East, the Committee for U.N. Integrity, the Committee of Concerned Scientists, the Universities’ National Anti-war Fund, and Scientists and Engineers for Secure Energy.

Following his retirement, Bloch began writing a book on statistical mechanics. However, he couldn’t complete it before his death. His notes were later organized by J. D. Walecka and published with the title ‘Fundamentals of Statistical Mechanics’.

Awards and Honor

Felix Bloch won the prestigious Nobel Prize in Physics in 1952, together with Edward Mills Purcell for the ‘development of new methods for nuclear magnetic precision measurements and discoveries in connection therewith’.

Bloch was a member of the National Academy of Sciences, the American Academy of Arts and Sciences, the American Philosophical Society, and the immensely prestigious German Honour Society called Pour le Merite.

Death and Legacy

Felix Bloch died of a heart attack on September 10, 1983, at the age of 77, in Zurich, Switzerland.

Bloch was the first director general of the European Organization for Nuclear Research (1954-55 CERN).

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