# PlanetPhysics/Felix Bloch

Felix Bloch (b. October 23, 1905 in Z\"urich--d. September 10, 1983) was a Swiss physicist, established in the U.S.A. His parents, Gustav and Agnes Bloch, were both Jewish, and he was educated at the Eidgen\"ossische Technische Hochschule in Z\"urich, but changed fields from engineering to physics.

### Education

He attended lectures and seminars by physical chemist/theoretical physicist Peter Debye and also by Hermann Weyl at ETH Z\"urich, and then by Erwin Schr\"odinger at University of Z\"urich. A neighbor student in such seminars was the American--Hungarian Jewish mathematician and mathematical physicist John (Janosh) von Neumann. Then he continued his physics studies at the University of Leipzig under Werner Heisenberg, earning his doctorate in 1928 with a famous doctoral thesis that established the quantum theory of crystalline solids, using what are now called ""Bloch waves to describe electron distributions in crystalline metals. Then, he also studied with Wolfgang Pauli in Z\"urich, Niels Bohr in Copenhagen and Enrico Fermi in Rome before he went back to Leipzig assuming a position as lecturer.

### Notable Achievements

In 1933, immediately after the nazis came to power, he left Germany, emigrating permanently to work at Stanford University in 1934, where he became the first professor for theoretical physics.
In 1939, he became a naturalized citizen of the United States and during WW II he worked on atomic energy at Los Alamos National Laboratory.
Then, he resigned the atomic energy project to join the radar war project at Harvard University where he capitalized heavily on the technical expertise with high power generators of radio waves that were then utilized by radar (based on the British radar invention by Sir John Randall, which is shared with the US during WW II). This technical experience allowed him and his close coworkers to cconcentrate on investigating the possibility of nuclear magnetic resonance (NMR) which he was able to demonstrate in 1944 independently of Purcell. Then, he proposed in 1946 his nuclear induction theory of NMR, together with his phenomenological (now called) Bloch equations which determine the time evolution of nuclear magnetization according to Bloch equations which determine the time evolution of nuclear magnetization. (Later, during 1960 to 1980, based on the same principles and theory on which NMR absorption and relaxation techniques were previously established, (N) MRI, or (Nuclear) magnetic resonance imaging applications were also developed for medical diagnosis, investigations and treatments; the latter however requires 2D-FT NMR to be able to reconstruct from 2D sections computed by 2D-FFT the 3D anatomical and also the dynamic/ relaxation structure that often confounds the X-ray trained radiologists).

### Awards and Recognitions

Felix Bloch and Edward Mills Purcell shared in 1952 the Nobel Prize for "their development of new ways and methods for nuclear magnetic precision measurements," or in other words for the first successful experimental demonstrations of the NMR phenomenon in wax and water, respectively. Notably, a famous Dutch physicist reported failed experiments to observe any NMR-related signal in 1942 using a microcalorimetric method on a single, high-purity crystal of (undoped) LiFl that had a very long spin-lattice relaxation time ($T_{1}$) which resulted in complete saturation, and thus no observable NMR absorption signal. The basic question of the observability of the NMR phenomenon in crystalline solids remained thus unanswered until 1944 when Herbert S. Gutowsky and Pake were able to demonstrate for the first time--and then publish in 1945-- the first dipolar-resolved NMR spectra in a dihydrated gypsum single crystal. However, the latter two were never recognized by the Nobel committee, nor was the discovery of the very important "chemical shift" effect reported for the first time by H. S. Gutowsky and Charles P. Slichter in the early 50's. The chemical shift--discovered and first reported by Gutowsky and Slichter--is currently the basis for all NMR spectroscopy, including 2D-FT NMR. In the US, a prominent NAS member was reputed to have said in the early 80's that "H. S. Gutowsky perhaps--according to many-- deserved not only one, but two Nobels awards", that cannot be however awarded posthumously. (Note, however that he was recognized by the Wolf Prize in Chemistry in 1983/84 for ""his pioneering work in the development and applications of nuclear magnetic resonance spectroscopy in chemistry . More specifically, the latter prize committee cited explicitly his truly outstanding physical chemistry research results as follows: Professor Herbert S. Gutowsky was the first to apply the nuclear magnetic resonance method to chemical research. His experimental and theoretical work on the \htmladdnormallink{chemical shift {http://planetphysics.us/encyclopedia/MolecularOrbitals.html} effect and its relation to molecular structure has provided the chemist with working tools to study molecular conformation and molecular interactions in solutions. Gutowsky's pioneering work on the spin-spin coupling effect developed this phenomenon into a `fingerprint' method for the identification and characterization of organic compounds. He was also the first to observe the effect of dynamic processes on the lineshape of high resolution nuclear magnetic resonance spectra, and exploited it for the studies of hindered rotation in molecules, Simultaneously with others he discovered the effect of the scalar and dipole-dipole interaction with unpaired electrons in solutions of paramagnetic ions.}
Interestingly, Professor Jean Jeneer who reported the first designs of 2D-FT NMR experiments --that are the basis of all current MRI medical applications, and also 2D-FT NMR structure determinations, for which several (5) Nobel prizes have been already awarded-- did not receive a Nobel award either; whereas in the previous case, the proximity to EU might explain the different treatment, in the latter, clearly the `chemical bias' against crystalline solids by chemists and physiologists--as well as other unwritten motives--may be the only possible explanation for the inequity involved, apart from the lack of a practical/experimental `proof-of-concept' in the latter case).
In 1954 and 1955, Felix Bloch served for one year as the first General Director of CERN, and then, in 1961, he was appointed Max Stein Professor of Physics at the famous Stanford University.