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The Early Years of NMR Spectroscopy in Germany  

by Harry Pfeifer      * 25. Februar 1929  † 28. September 2008      Picture and Wikipedia

The first nuclear magnetic resonance experiments in Germany were performed at the University of Leipzig in the summer of 1951 [1]. These experiments were stimulated by events that took place 24 years before: In the fall of 1927 Peter Debye had moved from the Swiss Federal Institute of Technology at Zürich (ETH) to Leipzig where he became Director of the Institute of Experimental Physics (see Figure 1) and where he had persuaded Werner Heisenberg to accept the professorship for theoretical physics.

Figure l. The Physics Institute of the University of Leipzig before the war. The view is from the Linnéstrasse. On the right-hand side, the villa of the director (1927, Peter Debye) can be seen; on the left-hand side is the large auditory and behind it the tower that housed the physics library

It was not surprising therefore, that Leipzig became an attractive place for young scientists and students of physics. Among them the most pro­minent was apparently Felix Bloch, who writes in his Reminiscences of Heisenberg and the Early Days of Quantum Mechanics [2] "... in October 1927 before the beginning of the winter semester, I left my nice home town (Zürich) for the first time to arrive on a cold gray morning in that rather ugly city of Leipzig... As soon as I had completed the simple formality of registering as a student of the university in the center of the city I went to the physics institute, which was located near the outskirts. It was an old building opposite a cemetery on one side and adjoining the garden of a mental institution on the other, but occupied by people who were far from being either dead or crazy ... Debye had the director's villa in a side wing, and for young bachelors like Wentzel and also Heisenberg upon his arrival there were small but comfortable apartments under the roof... These men were so entirely devoted to their science and their work spoke so clearly for itself that there was really no room or reason for any pretence, be it in the form of grand manners or false modesty...". In the following months Felix Bloch became the first student of Werner Heisenberg, and he finished his thesis on The Quantum Mechanics of Electrons in Crystal Lattices in 1928. After one year as an assistant to Pauli in Zürich and another year as Lorentz Fellow in Holland, Felix Bloch came back to Leipzig in the fall of 1930 as Heisenberg's assistant until Hitler succeeded in 1933 in forming a new Germany in his own frightful image.

Figure 2. The Physics Institute after the war. The view is parallel to the Linnéstrasse. In the ruin on the right-hand side, in front of the tower, the first NMR signals were observed in the summer of 1951

After the war, in October 1947 when I (H. Pfeifer) came as a student to the University of Leipzig, the famous institute of physics located near the outskirts in the Linnéstrasse 5 was only a ruin (see Figure 2). The large auditory, the director's villa, the large store rooms of scientific apparatus and most laboratories were completely destroyed. As a result, lectures were delivered at the institute of mathematics about one mile away where some rooms were also placed at the disposal of physicists including the director's office and the library. Fortunately, nearly 80% of the scientific books and journals were saved since the physics library was housed in the tower of the institute which survived the bombs due to its internal stability. In the ruin however, rain was destroying more and more of the remaining laboratories and mechanical workshops and I remember that in spite of the fact that all electrical equipment had been switched off, we observed a permanent electrical current of nearly 10 A at the main line supplying the ruin. Nevertheless it was an exciting time of renewal, and at the end of the 1940s we received all the issues of Physical Review which could not be delivered before due to the war and after-war Problems. About that time Artur Lösche had finished his thesis on birefringence induced by mechanical rotation of polar liquids and became an assistant at the institute of physics. Being responsible for the library, he organized a systematic study of these journals. During this study we became aware of the exciting experiments of the former Leipzig scientist Felix Bloch, and in the summer of 1950, A. Lösche suggested the search for nuclear magnetic resonance signals including preliminary experiments as a suitable topic for a diploma thesis. At this time I was students' assistant for the lectures in experimental physics delivered by the director of the institute, Professor Waldemar Ilberg, a physicist who had changed after the war from the electronic industry (radar research) to university. He proposed the study of the light efficiency of gas discharge lamps since this would be a problem of special importance for an industry which was beginning to start at this time from a very low level in Germany. As a young student, it was not very easy for me to come to a decision but finally I chose the 'entirely useless' search for signals stemming from the Zeeman energy of hydrogen nuclei. There were two further students, Lippmann and Weber, who also followed the suggestion of Dr. Lösche, so that we three started separately in September 1950 to find the nuclear induction signals which were described for the first time in 1946 independently by Felix Bloch et al. and E. M. Purcell et al. in the January issue of the Physical Review [3].

Figure 3. The first NMR spectrometer built 1951 in a laboratory of the University of Leipzig

For my studies I used an old electromagnet that had survived the bombardments of the Institute (December 4, 1943, February 19, 1944, and April 6, 1945) and with the direct current supply commonly available in Leipzig at this time it was possible to achieve a magnetic field of about 0.8 T with a gap width of 2 cm. Stimulated by a paper by A. Roberts [4] I decided to build a superregenerative detector (see Figure 3) and in this connection to study the nonlinear theory of electric oscillations established more than 20 years previously by van der Pol [5]. As a result of the latter studies it could be shown theoretically [6] why harmonic electric oscillations can be generated in the case of parallel resonant circuits only through a combination with a device whose negative differential electric resistance is achieved from the positive values via infinity, while for the other type of resonant circuits where the capacitor is in series with the inductance, the differ­ential electric resistance must be zero at the transition from plus to minus. These considerations, however, did not help as much as some hints that I received from A. Roberts as a response to a letter that I wrote to him concerning practical aspects of the superregenerative detector. At the end of June 1951- I do not know the exact date, but I remember that it was in the late evening - I was looking at an oscilloscope at the output of the detector and listening simultaneously to a loudspeaker parallel to it. Suddenly I heard a growl when I varied the magnetic field around a certain value. Apparently it was caused by the 50 Hz modulation of the direct current of the electromagnet and, as it should, the growl ceased immediately after removing the small glass tube containing a dilute aqueous solution of iron chloride from the magnet: it was the first nuclear magnetic resonance signal at that place which Felix Bloch had left in 1933 and the first observed in Germany. Unfortunately, when the director of the institute, who had heard of that experiment, came to the ruin at the Linnéstrasse 5 to see the NMR signal, I could not reproduce it. I was very ashamed, but  father-like and with a slight smile on his face he said, 'Oh. I do know this effect very well, we called it several years ago the "Vorführeffekt" (demonstration effect)'. Of course a few days later I observed the NMR signal again and started a systematic study that finally led to my diploma thesis [7]. In the following year the other two students also succeeded, and Dr. Lösche published the first original paper on NMR in German with the title Kernparamagnetismus und Hochfrequenztechnik. In 1953 another review by A. Lösche was published [9] and two original papers appeared in German about proton mag­netic relaxation in liquids by Krüger from Stuttgart [10] and about the measurement of the intensity of the Earth's magnetic field by NMR [11]. One amusing point is that in the latter paper the editor had changed the symbol Ø for the unit Oersted to the abbreviation Dmr for diameter so that the author and the readers of the paper were surprised to find that the total intensity of the earth's magnetic field at Leipzig had been measured by NMR to be 0.475 ± 0.078 'diameters'. In 1954 a short note by W. Müller-Warmuth from the University of Frankfurt/Main appeared about an electronic device of the bridging type for measuring NMR signals [12]. The thesis Freie Präzessionen kernmagnetischer Momente by Günther Laukien [13] was submitted to the TH Stuttgart in 1955. G. Laukien also wrote the contribution Kernmagnetische Hochfrequenzspektroskopie [14] for the "Handbuch der Physik" in 1957. Since then, as in other countries, the number of NMR papers from Germany increased nearly exponentially and a complete survey can be found in the book "Kerninduktion" which was published by A. Lösche [15] in 1957, being the third monograph on nuclear magnetic resonance spectroscopy that appeared after the  books of Andrew [16] and Grivet [17]. From March 31 to April 2, 1960 the First German Conference on rf Spectroscopy was organized at Leipzig, and in 1961, only a few weeks after the wall was built in Berlin, the Tenth Colloque AMPERE (after Paris 1952, Grenoble 1953, Paris 1954, Paris 1955, Geneva 1956, St. Malo 1957, Paris 1958, London 1959, Pisa 1960) took place in Leipzig with A. Lösche as chairman of the organizing committee.
 

References

[1]   H. Pfeifer in Encyclopedia of Nuclear Magnetic Resonance, Vol. 1, Historical Perspectives, John Wiley and Sons, Chichester, New York 1996; H. Pfeifer, Magn. Reson. Chem. 1999, 37, 154

[2]   F. Bloch,Physics Today, Dec. 1976, 29, 23. [3] E. M. Purcell, H. C. Torrey, and R. V. Pound, Phys. Rev. 1946, 69, 37, F.Bloch, W. W. Hansen, and M. Packard, Phys. Rev. 1946, 69, 127

[4]   A. Roberts, Rev. Sci. Instrum. 1947, 18, 845

[5]   B. van der Pol, Proc. Inst. Radio Eng. 1934, 22, 1051

[6]   H. Pfeifer, Z. Angew. Physik, 1954, 6, 508

[7]   H. Pfeifer, diploma thesis, Universität Leipzig, 1951 

[8]   A. Lösche, Nachrichtentech. Elektron. 1952, 2, 144

[9]   A. Lösche, Exp. Tech. Phys. 1953, 1, 19, 69, 128 

[10] H. Krüger, Kolloid-Z.. 1953, 134, 93 

[11] H. Pfeifer, Nachrichtentech. Elektron. 1953, 3, 371

[12] W. Müller-Warmuth, Naturwissenschaften 1954, 1, 368

[13] G. Laukien, PhD thesis, Stuttgart, 1955

[14] G. Laukien, in Handbuch der Physik, Vol. 38, 1

[15] A. Lösche, Kerninduktion, Deutscher Verlag der Wissenschaften, Berlin, 1957

[16] E. R. Andrew, Nuclear Magnetic Resonance, Cambridge University Press, 1955

[17] P. Grivet, La Résonance Paramagnétique Nucléaire, Paris, 1955