New Resonance

M i l e s to n e s

DOI: m iles tone 8 10.1038/nphys863 New resonance

If, during the 1920s and 1930s, the The effect itself was not entirely The coming atomic nucleus had seemed of interest new. In 1938, Isidor Rabi had used of the nuclear to few besides the (mostly) gentle- it to measure magnetic moments man scientists studying it, by the end of both atomic species in a lithium age was an of the Second World War its wider chloride molecular beam, receiving appropriate cue… importance was abundantly clear. the 1944 Nobel Prize in Physics for for arguably the The coming of the nuclear age was that advance. Even earlier, the Dutch most widespread an appropriate cue for the two papers physicist Cornelis J. Gorter had 7 practical that cleared the way for arguably the looked for the resonance of Li in most widespread practical application lithium fluoride and 1H in alum, using First NMR signals from water. Image reprinted with permission application of from Bloch, F., Hansen, W. W. and Packard, M. Phys. Rev. 70, of nuclear spin today: nuclear a calorimetric method. Hampered 474–485 (1946) [http://prola.aps.org/abstract/PR/v70/i7-8/ nuclear spin magnetic resonance (NMR) by experimental vagaries and limited p474_1] ; courtesy of the American Physical Society. today. spectroscopy. resources, he published a negative The 1946 work of Edward Mills result. (In later years, on receiving identification of free radicals. Zavoisky Purcell at the Massachusetts Institute a prize for his contributions to low- might also have been the first to see an of Technology and Felix Bloch at temperature physics, Gorter would NMR signal, but he did not follow it Stanford University gave new muse on his strange ability to miss out up, at least not with publications. Had relevance to one object of intense on groundbreaking discoveries in this the vicissitudes of the age been less, gentlemanly interest before the war; and other instances.) and the dissemination of scientific the Zeeman splitting of nuclear The innovations offered by Bloch information easier, his claim might spin states in a magnetic field and Purcell’s approaches were the have been better heard in the West. As (Milestone 1). The degree of transition to real liquid and solid it was, the 1952 Nobel Prize in Physics splitting at a particular magnetic systems, and, in Bloch’s case, the use went to Bloch and Purcell. field strength depends on the of an induction coil to pick up and Richard Webb, Senior Editor, gyromagnetic ratio of the nucleus. sharpen the resonance signal. These Nature News & Views In NMR, a second, transverse field opened the way for the use of NMR ORIGINAL RESEARCH PAPERS Gorter, C. J. at the characteristic (typically radio) in all manner of contexts, including Negative results of an attempt to detect nuclear spin-transition frequency produces in living tissue — where it became magnetic spins. Physica 9, 995–998 (1936) | Rabi, an absorption resonance — a power- the lynchpin of magnetic resonance I. I., Zacharias, J. R., Millman, S. & Kusch, P. A new method of measuring nuclear magnetic moment. ful way to identify the nuclei present imaging (Milestone 14). Phys. Rev. 53, 318 (1938) | Zavoisky, E. Relaxation in a sample. In 1944, although shielded in of liquid solutions for perpendicular fields. 1 J. Phys. USSR 9, 211–216 (1945) | Purcell, E. M., Purcell et al. brought protons ( H) the relative obscurity of Kazan in Torrey, H. C. & Pound, R. V. Resonance absorption in solid paraffin to resonance; Bloch the steppes of Tatarstan, the Soviet by nuclear magnetic moments in a solid. Phys. et al. did the same in liquid water. The physicist Yevgeny Zavoisky published Rev. 69, 37–38 (1946) | Bloch, F., Hansen, W. W. & Packard, M. Nuclear induction. Phys. Rev. 69, 127 coincident timing was no accident: the first measurements of an analo- (1946) | Zavoisky, E. Spin magnetic resonance the development of radar technologies gous effect involving electron spins. in the decimetre-wave region. J. Phys. USSR 10, during the war, for which several of Electron paramagnetic resonance 197–198 (1946) further reading Gorter, C. J. Bad luck in the researchers involved had won their depends on an atom possessing an attempts to make scientific discoveries. Phys. spurs, had made sources of radiofre- unpaired electron, thereby limiting Today 20 (1), 76–81 (1967) | Kochelaev, B. I. & Yablokov, Y. V. The Beginning of Paramagnetic quency radiation freely available for the range of its application, but Resonance (World Scientific, Singapore, 1995) the first time. making it useful for the detection and