History of NMR
Spectrometer development
 |  |  |
| 1970s - JEOL Ltd. (100MHz) | 1984 - WP 60 CW, Bruker (60Mz) | 1993 - Avance DRX, Bruker (300MHz) |
Chronology
1920's Physicists have great success with quantum theory
Quantum theory was used to explain phenomena where classical mechanics failed. This theory, proposed by Bohr, was particularly useful for the understanding of absorption and emission spectra of atoms. These spectra showed discrete lines which could be accounted for quantitatively by quantum theory. However, this theory still could not explain doublet lines found in high resolution spectra.
1921 Stern and Gerlach carry out atomic and molecular beam experiments
The basis of quantum theory was confirmed by the atomic beam experiment. A beam of silver atoms was formed in high vacuum and passed through a magnetic field.
1925 Uhlenbeck and Goudsmit introduce the concept of a spinning electron
The idea of a spinning electron with resultant angular momentum gave rise to the magnetic dipole moment.
1926 Schrödinger/Heisenberg formulate quantum mechanics
This new branch of quantum physics replaced the old quantum theory. Quantum mechanics was successful for understanding many phenomena but still could not account for doublets in absorption and emmision spectra.
1927 Pauli and Darwin include electron spin in quantum mechanics
1933 Stern and Gerlach measure the effect of nuclear spin
Stern and Gerlach increased the sensitivity of their molecular beam apparatus enabling them to detect nuclear magnetic moments. They observed and measured the deflection of a beam of hydrogen molecules. This has no contribution to the magnetic moment from electron orbital angular momentum so any deflection would be due to the nuclear magnetic moment.
1936 Gorter attempts experiments using the resonance property of nuclear spin
The Dutch physicist, C.J.Gorter, used the resonance property of nuclear spin in the presence of a magnetic field to study nuclear paramagnetism. Although his experiment was unsuccessful, the results were published and this brought attention to the potential of resonance methods.
1937 Rabi predicts and observes nuclear magnetic resonance
During the 1930's, Rabi's laboratory in Columbia University became a leading center for atomic and molecular beam studies. One experiment involved passing a beam of LiCl through a strong and constant magnetic field. A smaller oscillating magnetic field was then applied at right angles to the initial field. When the frequency of the oscillating field approached the Larmor frequency of the nucleus in question, resonance occurred. The absorption of energy was recorded as a dip in the beam intensity as the magnetic current was increased.
1943 Stern awarded the Nobel prize for physics
Otto Stern was awarded this prize 'for his contribution to the development of the molecular ray method and discovery of the magnetic momentum of the proton'.
1944 Rabi awarded the Nobel prize for physics
Rabi was given this prize for his work on molecular beams, especially the resonance method.
1945 Purcell, Torey and Pound observe NMR in a bulk material
At Harvard, Purcell, Torey and Pound assembled apparatus designed to detect the transition between nuclear magnetic energy levels using radiofrequency methods. Using about 1kg of parrafin wax, the absorbance was predicted and observed.
1951 Packard and Arnold observe that the chemical shift due to the -OH proton in ethanol varies with temperature.
It was later shown that the chemical shift for this proton was also dependent on the solvent. These results were explained by hydrogen bonding.
1952 Bloch and Purcell share the Nobel prize in physics
This prize was awarded 'for their development of new methods for nuclear magnetic precision measurements and discoveries in connection therewith'.
1953 A. Overhauser predicts that a small alteration in the electron spin populations would produce a large change in the nuclear spin polarisation.
This theory was later to be named the Overhauser effect and is now a very important tool for the determination of complex molecular structure.
1957 P. Lauterbur and C. Holm independently record the first 13C NMR spectra.
Despite the low natural abundance of the NMR active isotope 13C, the recorded spectra showed a signal to noise ratio as high as 50.
1961 Shoolery introduces the Varian A-60 high-resolution spectrometer.
The Varian A-60 was used to study proton NMR at 60MHz and proved to be the first commercial NMR spectrometer to give highly reproducible results.
