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Note on the Life and Work of Anatole Abragam

Serge Haroche
p. Quantum Physics

Notes de la rédaction

Source: La lettre, no. 33, May 2012

Texte intégral

1Anatole Abragam was born in 1914 in a middle-class Jewish family in Moscow, where he spent his early childhood and witnessed the initial years of Soviet Russia.

2He immigrated to France at age ten, with his mother and sister. His father, who had stayed in Moscow, was only able to join them in Paris eleven years later. From his childhood in Russia, he kept a perfect command of the language, as well as the essence of the Slavic soul, conveyed in his literature and poetry, which were part of him throughout his life.

3As soon as Anatole Abragam arrived in France, he rapidly adapted to his new world, learning to speak French fluently and without an accent within a few months. He performed brilliantly in secondary school at the Lycée Janson de Sailly, where he shone in mathematics and Latin. After completing his baccalauréat, he first turned to medicine, the profession of his mother, who was one of the first female doctors in Russia, but soon realized he was not made for a medical career and decided after a year to study physics. Too much of an independent mind to comply with the discipline of the classes préparatoires, he chose the university path.

4In the 1930s, despite a few distinguished professors, physics teaching in France was a very poor reflection of this discipline’s effervescence and revival, witnessed primarily in English-speaking countries and Northern Europe, where most scho­lars chased from Germany by the rise of Nazism had taken refuge. Quantum mechanics was still taught little or poorly in Paris and the young Anatole, with a sharp and critical mind, was well aware of the limits of the education that was being offered to him. He was unable to find a thesis supervisor at the Sorbonne capable of leading him beyond his Bachelor's, which he obtained with flying colours in 1936.

5He was starting to doubt his calling when the war interrupted his studies. He experienced the ‘phoney war’ and the German attack during his military service, without his unit being summoned to fight, and then hid out in the South, earning a living by giving Latin, maths and physics classes in private schools. He eventually took refuge in the Grenoble hinterland, joining the Free French Forces in the last year of the war.

6Aged 30, at the Liberation, he had neither a profession nor training in physics that lived up to his ambition, but new possi­bilities were opening up to him with the effervescence of France’s reconstruction. Unwilling to return to the Sorbonne and to his bad memories, he joined the École supérieure d’électricité (Supélec). There he learned the basics of radio-electricity and radiofrequency technology, which had made immense progress during the war, and knowledge of which was to serve Abragam later on. In 1947 his engineering degree allowed him to join the newly created Atomic Energy Commission. With three brilliant young graduates from the École polytechnique, he formed what they humorously called the “three musketeers” of the AEC, enthusiastically making up for lost time by studying the core texts of quantum physics in depth, using their complementary skills to translate them for one another from English, Russian and German.

7Most importantly, he obtained two assignments with leave of absence from the AEC, allowing him to travel abroad to complete his training as a researcher: first in Oxford, from 1948 to 1950, where he learned about electron paramagnetic resonance and based his thesis on original theoretical work on the subject; and then in Harvard, from 1952 to 1953, where he discovered nuclear magnetic resonance (NMR) under Edward Purcell, one of the pioneers of this discipline born in 1946.

8Back at the AEC, he was first asked to contribute to the nuclear and particle physics programmes that constituted the core mission of this organizsation, and worked in particular on designing a new accelerator. But he soon returned to the subject which had fascinated him since his time in America, the lighter physics of nuclear magnetism. In 1955 he created his own magnetism laboratory within the AEC, which, under various forms, was to be the world’s Mecca of NMR for the next 30 years. Thus, between ages 30 and 40, Anatole Abragam made up for lost time, becoming an internationally renowned researcher, recognized for his original contributions to the exploration of the properties of nuclear magnetic moments.

9His reputation was firmly established with the Principes du magnétisme nucléaire (Principles of Nuclear Magnetism), which he published in 1961, and which still constitutes a core reference fifty years later. Anatole Abragam’s great educational qualities shine through in this book, written in elegant English, for after his time at Oxford and Harvard, he spoke the language as well as he did Russian and French. In it he explains scientific calculations through images and analogies which lighten the text and make it easier for readers to understand. Anatole Abragam also wanted to express these educational qualities through direct teaching. From the mid-1950s, with other researchers from the AEC, including the three musketeers mentioned earlier, he invented high-level education designed as an introduction to modern physics, which was cruelly lacking­ in the regular curriculum of French higher education. The “informal” courses he and his colleagues gave for a few years to young researchers, including Claude Cohen-Tannoudji and Pierre Gilles de Gennes, and even to experienced scientists like Alfred Kastler and Jean Brossel, were the true precursors of the Graduate School education that was to develop in universities much later, in the mid1960s.

10But this was not enough to quench Abragam’s thirst to teach, and he dreamt of a professorship. University was not an option, as a thesis completed abroad, albeit in Oxford, would not afford him access to it. Alfred Kastler was the one who thought that the Collège de France was the solution to the problem and advised Anatole Abragam to apply! What institution could be better suited to his qualities than the Collège, which gives its professors total freedom in their teaching choices, allows them to express the full range of their theoretical and educational capacities, and above all as a legacy of François I’s distrust of the Sorbonne, does not require its professors to hold a degree from a French university. The matter was settled in 1960 when he was nominated for a chair at the Collège de France by Francis Perrin, not without all sorts of incidents that do not need to be discussed here.

11At the age of 45, Anatole Abragam, the late bloomer as he defined himself, became the young Chair holder of Nuclear Magnetism, which he remained for a quarter of a century. Every year he delivered highly valued education on diverse themes, stemming from his research at the AEC or the work of his colleagues, in France and throughout the world. During all those years, Anatole Abragam divided his time between tea­ching at the Collège de France and leading his research team at the AEC. For eight years, from 1962 to 1970, he was also Head of Physics at the AEC. This was an important administrative responsibility which allowed him to keep up to date on the evolution of many external research fields within and through which he contributed meaningfully to the evolution of the AEC. Along with the CNRS, the AEC became one of the most active multidisciplinary French research institutions. The reputation he acquired through the Collège de France, his research and his responsibilities at the AEC, came with numerous honours and distinctions, including entry to the Académie des sciences in 1973, nomination in several foreign academies and multiple international prizes, with only one exception, to which I will come back later. One distinction that was particularly significant for him was his nomination to the Pontifical Academy. A man of convictions, he nevertheless resigned a few years later to protest against John Paul II’s position on birth control.

12Drawing an outline of the major stages of Anatole Abragam’s career gives only a vague idea of his style and his important scientific contributions. He was an intuitive and prolific physicist, with a deep sense of aesthetics in science, always searching

13for the elegant idea and the simplest explanation, imagining new physical situations with a wealth of possible applications. A theorist before all else, he was very close to the experi­menters in his group, whose progress he followed attentively and with a critical mind. He kept himself informed on every detail, in which, he said, the devil was always hiding. It is difficult here for me to be more specific. I will simply say that he made crucial advances in our understanding of the phenomena involved in the magnetism of atomic cores in condensed matter, whether solid or liquid. These nuclei generally carry small magnetic moments (spins) associated with their kinetic moment. These magnets tend to orientate themselves within an external magnetic field or a field created by neighbouring magnetic moments. This orientation, thwarted by thermal agitation, can be modified by applying radiofrequency fields with the appropriate frequency, the very fields that the young Anatole learnt to produce and control in his years of engi­neering training at Supélec.

14By subjecting magnetic moments to such fields, Abragam and his colleagues (among them his collaborator for thirty years, Maurice Goldman) studied various effects related to the coupling of electron and nuclear spins with each other. They drew precise information on the structure of matter (the way in which these magnets are distributed) and on the dynamic mechanisms that disorientate the magnets, what we call their relaxation. They also invented ingenious methods for the dynamic polarization of these nuclear spins in an external field, transitorily obtaining much higher orientation rates than those observed in matter in its natural state. They were also able to produce a spontaneous orientation of nuclear spins in their internal field, what we call a state of nuclear ferromagnetism, and studied their properties.

15Anatole Abragam touched on many other research themes of the physics of nuclei and magnetism that I will not mention here. He nevertheless steered clear of two significant developments in NMR: the study of molecules of biological interest using this technique, and medical imaging. These were two fields within which pure physics relied on sciences in which he did not feel competent: biology and computing. It was these themes with significant applications in society that the Nobel committee distinguished when rewarding research on NMR, beyond the recognition paid to the pioneers of this field of physics, Edward Purcell and Felix Bloch. Abragam never hid the fact that he had hoped things would be different and that his more fundamental research would be recognized by this ultimate prize. He nevertheless took the Nobel’s decisions philosophically, even recognising the relevance of the choices made by the Stockholm committee which has always, by virtue of its statutes, distinguished a specific important discovery rather than crowned a whole career, no matter how brilliant. He comforted himself by humorously noting that, just like the president who had given France a young prime minister, he had given the Collège de France two young Nobel Laureates, since he was the one who, in the early 1970s, had suggested the creation of the Chairs of Pierre-Gilles de Gennes’ and Claude Cohen-Tannoudji, who were to accomplish the careers we know they have had.

16Apart from his personal scientific career, Anatole Abragam was one of the great craftsmen of the return of French physics to the highest level of research internationally. With a few other scientists of his generation, he contributed after the war to rebuilding the bridges between the community of French scientists and the major schools of global physics, particularly in the United Kingdom and the United States. They thus created the conditions that allowed the new generations of physicists, inclu­ding my own, to work competitively, in an environment that is conducive to research. I believe it would be appropriate in this eulogy to associate the memory of Abragam with that of other departed physicists of his generation, by recalling a few personal memories. The laboratory in which I did my Doctorate and in which I in fact still work was founded in 1950 by Alfred Kastler and Jean Brossel, who dedicated their careers to the study of the magnetism of atoms in their gaseous phase, as opposed to the atoms in condensed matter that Abragam studied. However these two physics have a lot in common, which explains why, from the 1950s, Kastler, Brossel and Abragam knew one another and held one another in high esteem, both on a scientific and a human level.

17I have already mentioned how useful Abragam’s lectures at the AEC had been to Kastler and Brossel, and especially to their student Claude Cohen-Tannoudji, who then used the theoretical tools developed by Abragam to elaborate his theory of optical pumping. One of these tools is the master equation, which provides a comprehensive and precise description of the behaviour of atoms in an electromagnetic field with thermal agitation. When I began working on my thesis with Claude, he introduced me to the beauties of the master equation and advised me to read the bible on the topic, the famous Principles of Nuclear Magnetism, enthusiastically recalling the atmosphere of the classes he had taken at the AEC ten years earlier, and which seemed to have an aura of legend. Later on Claude and I constantly used this famous master equation, initially established by Felix Bloch but explicated remarkably well by Abragam, and which serves to explain so many phenomena in magnetic resonance, atomic physics and quantum optics, and has thus been taught in the lectures of three generations of Chairs at the Collège.

18Once again I was first exposed to Anatole Abragam’s eloquence indirectly. In 1967, as Chairman of the French Physical Society, he had proposed to edit a collective volume to pay tribute to Alfred Kastler, who had just received the Nobel Prize for his discovery of optical pumping. Jean Brossel, who – in passing – had been unfairly left out of this prize, asked the young PhD student in his lab that I was at the time, to copy-edit the book. I immediately came across the following sentences in the preface written by Abragam, which I have condensed from his inimitable style:

19The custom of jubilee volumes is not unanimously recognized by the scientific community: an eminent physicist, whose collaboration was incautiously soli­cited, thought he could call this kind of book a collec­tion of second class articles written by first class physicists. I take exception to this assertion: at my own expense, I firmly insisted that second class physicists not be completely excluded from the collective work...

20I noted the self-mockery that I would find again later on in my direct interactions with Anatole, and at the same time, with some pride, the fact that as the author of a contribution to this book, I must belong to the same “second class” category as Abragam, which ultimately was not so bad. But it was mainly the wording he had used in French to say that he had firmly insisted, “j’ai tenu la main à ce que...”, which troubled me and which, knowing Anatole’s origins, I somewhat naively and imprudently attributed to a possible transcription of a Slavic expression into French. I therefore returned the proofs to Brossel with that sentence underlined in red and accompanied by a question mark in the margin. I still see Brossel’s smile and his eyes full of mischief, telling me with his South-Western accent (he had an accent, unlike the Russian Abragam): “you fool, don’t ever dare correct Anatole’s French...”

21Four years later, Claude Cohen Tannoudji firmly insisted that Abragam sit on my thesis jury, which is how I first came into contact with him. The questions he asked me during the ­thesis defence were both incisive and precise, attesting to the extreme attention he put into studying the work of a young researcher, the extent of his knowledge of physics, and his sense of humour. Our relationship deepened only much later. I had the opportunity of meeting him during sessions at the Académie des sciences, at conferences, and at informal lunches or dinners with visiting foreign colleagues in Paris. I was then able, like all those who knew him, to appreciate his extensive knowledge of Russian, English and French literature. Like many Russians of his generation, he knew the poem novel Eugene Onegin off by heart, he loved Tolstoy, Chekhov and Lermontov, and never tired of Shakespeare’s plays, whose lines he borrowed for the epigraphs of many chapters in his books. His knowledge of cinema was impressive, ranging from the silent cinema of his youth to Woody Allen, the Coen brothers and the Marx brothers. He had a devastating sense of humour and rarely missed an opportunity to make a joke, even at a colleague’s expense. He had known all those who mattered in physics world-wide and had a story to tell about each of them. He also had an inexhaustible wealth of anecdotes illustrating all sorts of situations in the life of science, borrowed from the Jewish humour that had never left him. In Abragam’s group, the almost automatic appearance of all sorts of technical diffi­culties that usually arise when researchers seek to concretely perform an experiment inspired by a fine theoretical idea, had been called the “Margaret effect”, with reference to the story he liked to tell: a matchmaker, an essential character in Eastern European Jewish folklore, got it into her head – a very nice theoretical idea – to marry a son from a good family with the nice princess, the Queen of England’s sister, whose love affairs were being written about in all the newspapers at the time. Putting her idea into practice, and coming out of a long interview with the boy’s family whose reluctance she successfully overcame after long efforts, the matchmaker exclaimed, rubbing her hands together: “phew, that’s half the work done”.

22Another one of Anatole Abragam’s stories came back to me recently as a sensational scientific announcement was made. A famous American physicist had published an article announcing the observation of a free quark. As this is an elementary particle whose theory only envisages its existence in bound form, hidden­ in atoms’ nuclei, this astounding news put the physicist in the media spotlight for a while. The experiment, which was very tricky, could however not be reproduced by other researchers and the free quark, probably an artefact, soon disappeared from the newspaper headlines, as well as from physicists’ conversations. This fleeting scientific bliss inspired Abragam to think of a metaphor in which the elusive quark is turned into a diamond: on a Friday evening, just before closing time, a man walks into a famous jewellery shop with a beautiful young lady who chooses a splendid ring. Our man pays for it by cheque on the spot. The salesman tells him that given the time, it is impossible for him to obtain confirmation from the bank that the check can clear. “Never mind”, answered the man, “keep the ring until Monday and I will come and fetch it when you have the bank’s agreement”. He then walks out arm in arm with the fulfilled

23beautiful young woman. When he returns on the follo­wing Monday, the salesman regretfully tells him that the bank refused the check. “I feared so”, said our man with a smile, “but what a great weekend I’ve had!”. The announcement of neutrinos faster than light would undoubtedly have inspired Anatole to come up with a similar kind of fable.

24But beneath the brilliant, even caustic character there was also a warm, down-to-earth man in private. Abragam was kind and considerate with his students, his colleagues and his friends. He had met his first wife, Suzanne, during the war and they remained happily married for close to half a century. Despite her frail health, she was her husband’s companion in all the travels and public appearances that came with his professional life.

25When he became a widower in 1992, Abragam made a donation to the Académie des sciences to set up the Suzanne and Anatole Abragam prize which, by rewarding a young researcher every year, sought to perpetuate within the scientific community the memory of a united couple, which remained without children, to his great regret. He spoke about his departed companion with emotion that clearly conveyed his love and admiration. The private man also appeared in his affectionate behaviour towards his second wife whom he married in 1996, Nina, a Russian physicist with whom he lived a long happy old age, “waiting”, as he said it himself, “for the end of the story with serenity and no impatience”. Finally I will mention the special ties Abragam had with the Collège de France. Of all the honours he received in his long career, his title as Professor at the Collège gave him the grea­test pride. He cherished the opportunity our institution had given him to meet so many exceptional colleagues, namely from the humanities and social sciences (this was the time of Maurice Merleau-Ponty, Roland Barthes, Michel Foucault and Raymond Aron, all of whom he held in very high esteem. He saw our mission to teach science in the making to all as a noble one, and valued the unique chara­cter of our institution on the global academic scene. Two anecdotes on the subject, taken from his 1987 autobiography, De la physique avant toute chose (Time Reversal, an Autobiography), illustrate Anatole Abragam’s culture and spirit, and what he thought of the Collège’s original mission.

26The first relates to our motto, “Docet omnia”. Anatole tells us that in 1980, it was with great ceremony that the Collège received the President of the Republic. As a man of culture, with his eyes probably already on the Académie française that was to welcome him a few years later, the latter ventured to complete our motto, in his speech delivered before the professors, with the additional idea that we teach everything to everyone, thus transforming it into “Docet omnibus omnia”. When this speech was to be published, Anatole was more than happy to remind the literary professors, who he claims had not noticed (although this is probably too good to be true), that the presidential omnibus was incorrect and that one should say “Docet omnes omnia” according to the immemorial rule of the double accusative (following the classic example “Doceo pueros grammaticam”). Anatole adds that a highly political discussion ensued on whether to consult the presidential cabinet before making the correction, and that the Administrateur wisely decided instead to correct it without saying anything. The second anecdote recounts a dialogue between an American colleague and a professor at the Collège who was trying to explain to the former what our institution is. The American, who thought he had understood, exclaimed: “the Collège de France is like the Princeton Institute for Advanced Study!” This comparison, which portrays us as a copy of a foreign institution created four centuries after ours, reminded Anatole of a remark by a person who saw Hamlet and thought the author must have read a lot of Freud.

27Those who knew Anatole Abragam remember his elegant ­silhouette, his smile, his fine, distinguished moustache, his gaze which could in turn be kindly or mischievous, and his clear and well-articulated voice that so often resonated in this room. A great scholar who has had considerable influence on physics through his scientific work, his teaching and his leadership and administrative research functions, Anatole Abragam was an honest man in the classical sense of the term, a man of great culture and convictions. His influence in the academic world and his reflections on research and university also made him a statesman of science, as the Americans would say. The Collège de France can pride itself on having counted him as one of its own.

Anatole Abragam was born in Moscow on 15 December 1914. He passed away on 8 June 2011 at age 96. A graduate from the École supérieure d’électricité, he was Head of Physics at the Atomic Energy Commission from 1962 to 1970. Appointed Professor at the Collège de France in 1960, he held the Chair of Nuclear Magnetism until 1985.

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Serge Haroche, « Note on the Life and Work of Anatole Abragam », La lettre du Collège de France [En ligne], 7 | 2015, mis en ligne le 03 novembre 2015, consulté le 25 avril 2017. URL : http://lettre-cdf.revues.org/2728

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