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NMR_history - Varian

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Felix Bloch Felix Bloch developed the concept of what he called “Nuclear Induction” during World War II while working on radar counter measures at Harvard Radio Research Laboratory. This idea of Nuclear Induction later became know as Nuclear Magnetic Resonance.
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Page 1: NMR_history - Varian

Felix BlochFelix Bloch developed the conceptof what he called “NuclearInduction” during World War IIwhile working on radar countermeasures at Harvard RadioResearch Laboratory. This idea of Nuclear Induction later becameknow as Nuclear MagneticResonance.

Page 2: NMR_history - Varian

Felix Bloch and William HansenProfessor Bloch returned to Stanford University after the end of World War II and, with the help of Professor William Hansen, developed plans for the firstNMR experiments.

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First NMR signals, 1946The nuclear magnetic resonance of protons in water was first detected in earlyJanuary 1946 by graduate student Martin Packard, working with Bloch and Hansen F. Bloch, W.W. Hansen, and M. Packard, “Nuclear Induction,” Phys. Rev 69,127 (1948).

Proton signal from water at 7.76 MHz, sinusoidal field modulation,Bloch, Hansen, and Packard Phys. Rev. 70, 474 (1946)

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Early NMR Probe and ElectronicsBloch’s group was the first to see the NMR signal from water. This early version of an NMR probe was build by William Hansen.

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Russell VarianRussell Varian returned to Stanfordin July 1946 from his radar workat Sperry Laboratories on LongIsland. He believed that nuclearmagnetic resonance would be usedfor more than just the measure-ment of magnetic field strengthand nuclear magnetic moments,and felt that NMR would be evenmore useful in chemical analysis.Bloch and Hansen were notconvinced but requested that heprepare an initial draft of a patentfor them.

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Bloch-HansenPatent, 1948With help from Bloch, Hansen, andothers, Russell Varian filed apatent in October 1948, entitled“Method and Means forCorrelating Nuclear Properties ofAtoms and Magnetic Fields.”Subsequent patents were laterissued to include electron spinresonance.

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Varian Associates Headquarters in 1948Varian Associates was incorporated in April 1948. One of the stated purposes ofthe company was to perform “research in chemistry, to measure the gyromagneticratio of the nuclei of atoms, and to use the gyromagnetic properties of atoms tomeasure magnetic fields for other purposes.” The company boasted $22,000investment of capital and 6 full time employees.

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Chemical Shift Observed in Ethanol, 1951At Stanford in 1951, Jim Arnold, Martin Packard, and Shrinavas Sharmatiobserved a chemical shift between protons within the same molecule J. Chem.Phys.,19,507 (1951). Russell Varian had long been an advocate of NMR, and thesignificance of this advance and its potential impact on chemical analysisprompted the initiation of an active NMR applications development effort,headed by a new employee Jim Shoolery.

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First NMR Applications Laboratory, 1952The first commercial NMR spectrometer, the Varian HR-30, was installed at Humble Oil company in Baytown, Texas in September 1952. Jim Shoolery, with helpfrom Virginia Royden, opened the Varian NMR Application Lab in January 1953.

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First CommercialTechnicalInformationBulletin on NMR,1953In July of 1953, Jim Shoolery andEmery Rogers published the firstNMR Technical InformationBulletin, which described highresolution NMR and itsapplications to chemistry.

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Sample Spinning,1954The resolution of NMR was greatlyenhanced by the introduction ofsample spinning, a conceptdeveloped by Felix Bloch and firstdemonstrated by Wes Andersonand Jim Arnold at Stanford. Thedrawing shown here is from thepatent filed for Bloch by Varianin 1954.

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Super High Resolution NMR in 1956Ethanol spectra from 1954 and 1956 show the improvement in resolutionbrought about by the introduction of sample spinning, higher magnetic field,and the use of the “Super Stabilizer” to overcome magnetic field jitter.

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Field/Frequency Lock, 1956Russell Varian developed the concept of the field/frequency lock utilizing afeedback mechanism. This drawing is from a patent filed in 1956.

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The Varian A-60, 1961The Varian A-60 NMR spectrometer, introduced in 1961, was designed forthe laboratory chemist. It included calibrated chart paper and a built-insignal integrator.

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The HR-100, 1959Iron magnets reached their practical limits for use in NMR at a proton frequencyof 100 MHz. The Varian HR-100 was the world leader in chemical shift dispersionand sensitivity from the time it was introduced in 1959 until the first high-resolution superconducting NMR magnet was built at Varian in 1962.

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The First HighResolution“Supercon” NMRAfter receiving his PH.D. atStanford under Professor Block,Harry Weaver joined Varian in1954. Here he developed the firstsuperconducting NMR magnetusing a niobium-titanium alloy.The result was the Varian HR-200,the HR-220 (shown here) and laterthe HR-300 high resolution NMRspectrometers.

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FT NMR Concept, 1956Russell Varian proposed the first applications of Fourier transform principles toNMR as a means to increase the sensitivity of NMR spectrometers. This patent,filed in 1956, described a wideband noise source for NMR signal excitation andheterodyne mixing of the detected signal down to audio. Although severalmethods were described for the extracting amplitude vs. frequency information,a practical implementation would wait for nearly a decade.

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Pulse-Excited High Resolution NMR, 1964This diagram from Wes Anderson’s engineering notebook, dated June 3, 1964,outlined the idea of pulse-excited high resolution NMR spectroscopy. Thepractical application of the idea was later implemented by Richard Ernst,working in Anderson’s laboratory.

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FT NMR in Practice, 1965Ernst’s apparatus worked well, but was limited by the computing technology of 1965. NMR data was read out of the C-1024 averaging computer on papertape, transferred to punched cards, and taken to the IBM 7090 computer in an adjacent building. Several days later, after waiting for payroll and factoryinventory processing, the Fourier transform was complete.

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Sensitivity Advantage of FT NMRThe two spectra of Progesterone, taken in the same total time, were used by Ernstand Anderson to illustrate the sensitivity advantage of Fourier transform NMR.


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