JOHN CHARLES POLANYI
(January 23, 1929 - )
Killam Laureate, 1988
John Charles Polanyi was born in Berlin, Germany, of Hungarian parents, Michael Polanyi and Magda Elizabeth (Kemeny) Polanyi. His family moved to Manchester, England, when he was four years old. His father, Michael Polanyi, was successively Professor of Chemistry and of Philosophy at Manchester University. John entered Manchester University, from Manchester Grammar School, in 1946, just in time to attend his father's last lectures on the subject of chemistry, given to the first year.
In English universities at that date, "The Prof.'s" interests coloured the activities of the entire department. When, in 1947, Michael Polanyi moved over to the Humanities, he left behind an academic staff that was devoted in large part to the exploration of the molecular basis for simple chemical reactions. John Polanyi's research supervisor was a spirited ex-student of Michael Polanyi, Ernest Warhurst. Warhurst had obtained his doctorate using the "sodium flame" apparatus which had enabled Polanyi Sr. and his co-workers to determine the probability that a collision between a sodium atom and a molecule would lead to reaction. He put Polanyi Jr. to work measuring the strengths of chemical bonds by pyrolysis (thermal dissociation); this study led to Polanyi's Ph.D. in 1952.
John Polanyi credits these years at Manchester University with having supplied him with the right questions to ask. The molecular basis for chemical reaction became the subject of the work for which, thirty-five years later, he received the Nobel prize.
He recast the questions that he had heard discussed in his student days so that they provided a fitting challenge for the coming period. In Manchester, the main focus was upon the mystery of overall reaction rate. Would a molecular collision of a given energy result in the formation of a new chemical species, or would it not? The time seemed opportune to ask, and perhaps answer, the further question: what types of forces operating during a molecular collision are the most conducive to reaction? The easiest way to learn something about this would be to study the motions of newly-born reaction products, since the forces operating in the "transition state" (part way between reagents and products) would imprint themselves on the products.
During his postdoctoral work with E.W.R. Steacie at the National Research Council of Canada's laboratories in 1952-1954, Polanyi became increasingly convinced that this was the right question to be asking. He also became convinced, for the first time, that he would like to be the person asking the question. His sense of vocation had been slow in coming. As a student at Manchester, he was interested in politics (editing a newspaper) and in writing (a narrative poem that he wrote as a graduate student covered a page in the New Statesman and Nation, to his delight) but only peripherally interested in science.
In Ottawa at the National Research Council (NRC), he was intoxicated by the experience of living under blue skies and, feeling permanently on holiday, he began to enjoy his work in the laboratory as never before. With Steacie's blessing, he embarked on some calculations to see whether the reigning theory of reaction rates, the so-called "Transition State Theory", had predictive power. He came to the conclusion that the theory was built on quicksand, since knowledge of the forces in the transition state region was lacking. In 1954, at the close of his two years at NRC, he spent a few months enjoying the hospitality of Gerhard Herzberg's laboratory where he assembled spectroscopic equipment to probe vibrational and rotational excitation in molecular iodine. As he put it subsequently, "some unseen hand must have been guiding me", since this work led him further along the way to measuring the corresponding types of motion in reaction products.
The same hand may have guided Polanyi to Princeton, where he spent two further years, 1954-1956, still as a postdoctoral fellow. Though he went there at the invitation of Sir Hugh Taylor, his main interactions were with two associates of Taylor's: Michael Boudart and David Garvin. Together with James McKinley, these workers were studying vibrational excitation in the products of the reaction of atomic hydrogen with ozone. The reaction gave rise to an orange glow as the highly vibrationally excited reaction product made spontaneous transitions directly to very low states of excitation. Though Polanyi did not participate in this experiment, he was influenced by it. If these three workers could see "high overtone" vibrational transitions, then it should be possible to detect the much more probable "fundamental transitions" due to smaller changes in vibrational state. These would give rise to infrared emission. Polanyi took this idea with him to Toronto, when he moved there as Lecturer in Chemistry at the University, in 1956.
With his first graduate students, he looked for enhanced reaction rate in vibrationally excited hydrogen formed in a discharge, and also for vibrationally excited hydrogen chloride in the product of the exothermic reaction of atomic hydrogen and molecular chlorine. It was this second line of experimentation, first reported in the literature in 1958, that set Polanyi and his group on the path to their main work.
The experiment was simple and (for sound reasons) inexpensive. Atomic hydrogen, formed in an electric discharge by power taken from a neon sign transformer, was mixed with a flow of chlorine gas at low pressure in a vessel equipped with sodium chloride windows that transmitted infrared. An infrared spectrometer, shared as an analytic tool by the entire department, was borrowed and positioned in front of the sodium chloride window. With the reagent gases flowing, the reaction vessel, which remained cold to the touch, gave out an infrared spectrum indicative of the presence in the vessel of hydrogen chloride at a temperature of thousands of degrees. This molecular excitation was chemical in origin and constituted "infrared chemiluminescence".
The 1958 communication by Polanyi and his student J.K. Cashion ended with the statement that "The method promises to provide for the first time information concerning the distribution of vibrational and possibly rotational energy among the products of a three-center reaction".
It took a further decade, and the work of a substantial group of graduate students to fully realise this goal. It was necessary to combat the effects of vibrational and rotational "relaxation". This was achieved most effectively by using sprays of reagent gases that crossed in the centre of an evacuated chamber. The infrared emission from new-born reaction products was recorded. The products were then removed at the liquid-nitrogen-cooled walls of the vessel before they had time to relax. This "arrested relaxation" approach led to the first quantitative determinations of "detailed rate constants", that is to say, the rates of reaction into specified states of product vibrational, rotational, and (hence) translational excitation.
This last item of informationtranslational excitationprovided common ground between the infrared chemiluminescence studies in Polanyi's laboratory and the crossed molecular beam studies which constituted the major altemative route to such measurements. The crossed-beam method, in which the prime measurables are product translational and angular distributions, came to maturity in the hands of D.R. Herschbach and Y.T. Lee with whom Polanyi shared the 1986 Nobel prize in Chemistry.
A major technological outgrowth of Polanyi's work first became evident only two years after the publication of the initial report of infrared chemiluminescence. In 1960 Polanyi submitted a paper to Physical Review Letters entitled "An Infrared Maser Dependent on Vibrational Excitation". This extended the prior proposal by C.H. Townes and A.L. Schawlow (in 1958) for what today we call a 'Laser'.
Townes and Schawlow had envisaged a medium made up of electronically excited species. Polanyi proposed that the medium be composed of vibrationally and rotationally excited molecules. The suggestion was tempting for a variety of reasons. In the first place, because of a phenomenon that Polanyi termed "partial population inversion", a lasing medium could be obtained by the simple process of (partially) cooling a hot gas. Secondly, a chemical reaction could be used to generate the lasing medium; today this is known as a "chemical laser". Additionally, Polanyi noted that such lasers should exist naturally in the upper atmosphere.
Physical Review Letters rejected the paper as lacking scientific interest. Shortly thereafter they rejected T. Maiman's report of the first operating laser, on the same grounds. Polanyi read about this second rejection, quite by chance, while holidaying on an island in Georgian Bay. On returning to Toronto in September of 1960 he submitted the identical manuscript to the Journal of Chemical Physics, where it was promptly published.
Since then, vibrational lasers and, in particular, chemical lasers (due, respectively, to C.K.N. Patel and G.C. Pimentel) have developed into the most powerful sources of infrared radiation. Polanyi is fond of asking sponsors of basic research who insist on evident promise of applications, whether they would have been far-sighted enough to support studies of barely detectable luminescence as a means to the development of the most powerful lasers in existence.
Despite its simplicity, the infrared chemiluminescence approach provided the most complete and detailed product energy distributions available for any chemical reactions. As a consequence, they were widely used as a testing ground for theories of the molecular mechanics of simple exchange reactions. Polanyi's group was active from the outset of its experimental program in attempting to link the underlying pattern of forces to the molecular motions by means of computer modelling.
The method used depended upon the happy circumstance that high-speed computers made it possible to solve the equations of motion for the reacting particles. The interplay of theory and experiment led to a number of simple insights. In endothermic (uphill) reactions, the energy in the transition state is most effective if it stretches the bond under attack, that is, if it is vibrational. Reagent motion is channelled through the transition state so as to become a similar type of motion in the products (translation into translation, vibration into vibration). Commonly, a molecule can be approached in two different ways to yield chemically the same product; this implies the existence of two different transition states which give rise to two patterns of motion in the product (a phenomenon termed "microscopic branching").
The infrared chemiluminescence approach was not restricted to the determination of product excitation. It could also be used to measure the effect of varying reagent vibrational and rotational excitation on reaction probability. This was achieved by using a prior reaction to generate infrared chemiluminescence and then recording the "chemiluminescence depletion", that is, the extent of reaction from the various states of vibrational and rotational excitation when pulses of a further reagent were introduced.
In more recent times, Polanyi's research interests have moved beyond the studies of reaction dynamics cited by the Nobel Foundation. In one recent line of work, the objective has been to develop what is termed a "spectroscopy of the reactive transition state". The hope is that one will be able to gain an insight into the molecular dance in chemical reaction by observing the molecular partners while they are on the stage, rather than in the wings before or after the dance is over. (This simile is a favourite one of Polanyi's, acknowledged at a gala performance of the National Ballet of Canada in 1987 at which Polanyi was invited, briefly, to observe the ballet from centre stage.)
In a second expanding line of research, members of Polanyi's group are developing a photochemistry of the adsorbed state. With the aid of ultraviolet laser radiation, they induce reaction between neighbouring molecules held at a solid surface. By means of this surface aligned reaction ('SAP'), they believe the molecules can be positioned at will and subsequently be induced to react in a determined way. To the extent that this succeeds, the dynamicist has become choreographer.
In the late 1950s, Polanyi became convinced of the need for scientists to involve themselves in public affairs, as they relate to the problem of survival in an age of nuclear weapons, and to the management of other equally powerful technologies. He has published some seventy articles on this and related questions, and has given many times that number of talks. In 1960 he became the founding chairman of the Canadian Pugwash Group and continued to hold that position until 1978. In 1978 he chaired an international symposium on 'The Dangers of Nuclear War', that led to a book of that title. He has been an active member of the American Academy's Committee on International Security Studies and also of the Canadian Centre for Arms Control and Disarmament.
In a different facet of his interests, he has been a founding member of the Royal Society of Canada's Committee on Scholarly Freedom and of the Canadian Committee of Scientists and Scholars. These activities have left time for involvement in the ongoing Canadian debate regarding science policy from the time of the Montagne Report two decades ago to the time of his recent involvement, at its formation, in the National Advisory Board on Science and Technology (NABS) chaired by the Prime Minister. Polanyi has continually stressed that high qualilty science is a necessary investment in the future. To the cry for "relevance" in basic science, he has responded that "nothing is more irredeemably irrelevant than basic science".
John Polanyi was married in 1958 to "Sue" Davidson (Anne Ferrar Davidson) of Toronto, a musician and piano teacher. John Polanyi describes himself as a musical ignoramus. His aesthetic pleasures come from art, literature, and poetry. He and his wife have written words and music, respectively, for skits which have been performed professionally. In a more active vein, John Polanyi has outgrown his youthful enthusiasm for white water canoeing and aerobatics in favour of skiing and walking. John and Sue have two children, Margaret, a journalist, and Michael, a physicist turned political scientist.
The award of the Nobel prize in 1986 to Polanyi, D.R. Herschbach, and Y.T. Lee was for contributions to "the development of a new field of research in chemistryreaction dynamics". In particular, Polanyi was cited for "the method of infrared chemiluminescence, in which the extremely weak infrared emission from a newly-formed molecule is measured and analysed", and for his application" this method to elucidate the detailed energy disposal during chemical reactions Polanyi has received many honours. A partial list includes the Marlow Medal of the Faraday Society in 1962, the Steacie prize for the Natural Sciences (with N. Bartlett) in 1965, the Tory Medal of the Royal Society of Canada in 1977, the Wolf prize (shared with G. Pimentel) in 1982, the Nobel prize in Chemistry in 1986, the Isaac Walton Killam Memorial prize in 1988, and the Royal Medal of the Royal Society of London in 1989. His list of named lectureships is extensive. The tally of honorary degrees comprises twenty-three in Canada, the United States, the United Kingdom, Israel, and Italy. The Government of Canada appointed him an Officer of the Order of Canada in 1974 and a Companion of the Order of Canada in 1979. He was made a Fellow of the Royal Society of Canada 1966, the Royal Society of London in 1971, the Royal Society of Edinburgh in 1988, a Foreign Member of the American Academy of Arts and Science in 1976, a Foreign Associate of the (U.S.) National Academy of Sciences in 1978, and a Member of the Pontifical Academy, Rome, 1986.
Canada has been rather infrequently represented on the platform in Stockholm: once for medicine, once for peace, and now twice for the physical sciences. Consequently, the status of Nobel Laureate carries special rewards in the form of public acclaim and special responsibilities due to public demands. In a speech of March 4th, 1987, the Prime Minister of Canada quoted John Polanyi: "We in Canada must have flourishing science in addition to vigorous technologybecause a nation is more than a machine for creating wealth. Science is the glory as well as the terror of mankind. Our respect for ourselves as a people requires that we, as a prosperous and civilised nation, contribute to this central strand of twentieth century culture."
Polanyi's fervent hope is that one can combine the necessary activity of speaking for science with the more congenial one of doing it.
Source: Kenney-Wallace, G.A., MacLeod, M.G., Stanton, R.G., Eds. In Celebration of Canadian Scientists: A Decade of Killam Laureates. Ottawa: The Charles Babbage Research Centre, 1990.PRINTING INSTRUCTIONS: This site has been designed using frames. Before using the print command, click on the area you want to print.