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Posted by on May 18, 2011 in Some reminiscences | 0 comments

The Success of NMR — Good Science

Galileo before the Holy Office, a 19th century painting by Joseph-Nicolas Robert-Fleury.

Galileo before the Holy Office, 19th century painting by Joseph-Nicolas Robert-Fleury.

Although we are inured to believe that scientists are always open to new ideas, in fact history shows that major shifts in thinking do not catch on fast, and are often met with skepticism and rejection.  Looking back, we can think of the ordeal Galileo faced; Charles Darwin’s Trials; the intransigence of Ernst Mach when he opposed the corpuscular nature of matter; and those today that reject the evidence of global warming.

My research was primarily on the theory of Nuclear Magnetic Resonance (NMR) until I changed to the foundations of quantum mechanics.  I will discuss the reasons why I left NMR, which is an example of one of the most successful consequences of fundamental research, to the foundations of quantum mechanics, which has been controversial from it inception. First, however, the success of NMR.

For me, in 1999 after spending most of my academic life (and about 130 papers) on the theory and NMR I decided that the field was well established and had moved from fundamentals to R&D, just as X-ray crystallography had done 20 years earlier.  This does not mean that NMR is not a fantastic tool, but just that I was motivated to change fields. NMR provides, however, an excellent example of how a new discovery can successfully evolve.

NMR moved from fundamental research in 1948 when Edward Purcell, Robert Pound and Felix Bloch spent leisurely time seeing if it were possible to make hydrogen nuclei (protons) resonate.  They did not envision that NMR would become one of the major tools in science and were involved only in fundamental physics research.   Soon after their success, chemical shifts were discovered in the 1950’s which revolutionized the structure determination of proton-containing compounds.  This motivated further technical and theoretical developments.  In the 1970’s continuous wave NMR (CW-NMR) was replaced by pulsed Fourier Transform FT-NMR, thereby opening up a huge range of low sensitivity nuclei and extending applications from protons: NMR was applied to gases (M. Bloom) starting in the 1960, and by many researchers to both liquid and solid state NMR which has grown into an invaluable tool in almost every area of science research.

Two dimensional NMR (2D-NMR) quickly followed from the remarkable theoretical musings of Jean Jeener: ideas that were experimentally developed by Richard Ernst and others, and taken to new levels of sensitivity and resolution with the ability to study structure, function and kinetics.  This moved NMR from chemistry to biochemistry, into the life sciences and, finally, with the founding work of Raymond AndrewsPaul Lauterbur, and Sir Peter Mansfield culminated in the development of non-invasive Magnetic Resonance Imaging (MRI) (with the word “Nuclear” removed to placate the masses).

An aspect of NMR is “spin gymnastics” which refers to our ability to make spins flip and flop and jump and turn as they respond to pulses and couplings.  Raymond Freeman took this to a high level of visualization so that it was possible to follow the transfer of spin polarization from one spin to another.  The efforts by the many researchers in the area led to multidimensional NMR and techniques like COSY, TOCSY and NOESY, to mention only three.

After being involved in this golden era of NMR development, in the late ‘90s I realized that the theory was well established, and the next logical step was to increase magnetic field strengths and improve the electronics of pulse generation, and computer control.  As the field strength increases, the theory of NMR gets simpler due to the weak coupling between spins and the lattice.

I had worked with spins my whole life, and so this let me to look at the emerging field of quantum information. But I quickly got bogged down with non-locality.

I will say something about that next.

I mentioned Felix Bloch above, and I met him when I was a post doc. at the Kamerlingh Onnes Labs in Leiden. He gave a Colloquium Ehrenfestii in 1972. I think some time I will reminisce about that meeting and the talk that he gave “The early days of magnetic resonance at Stanford”

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