Presentation Speech by Professor Sture Forsén of the Royal Academy of Sciences

Translation from the Swedish text

Your Majesties, Your Royal Highnesses, Ladies and Gentlemen,

A burning flame – a little everyday miracle that has astonished and fascinated most of us. A chemical reaction that produces heat and light and that during historical times has modified the conditions of life for mankind and made developing civilizations possible even on our northerly latitudes. But at the same time also a chemical transformation in which the products formed slowly have modified our atmosphere and most likely will also affect the earth’s climate.

From the point of view of natural science a burning flame is an intriguingly complex phenomenon. Oxygen molecules in air react with carbon and hydrogen in organic molecules. A manifold of primary products are formed, often unstable and reactive. Atoms are torn away from their parent molecules. The products of one reaction become the reactants of another. Dozens or even hundreds of molecular reactions occur in parallel. It is a scientific challenge to unravel the details of these transformations.

Let us assume that we choose for our study only one of the many chemical reactions that take place in a flame. Superficially this reaction may appear very simple and easy to understand. At a closer look, however, we find that Nature is elusive and complexity still prevails. Many difficulties await him who would like to study chemical reactions in their most intimate molecular details. The reaction event proper is a molecular drama that takes place under an exceedingly short time span – of the order of a millionth of a millionth of a second – times scientists refer to as a “picosecond”. How is it at all possible to obtain detailed information of what goes on under such short time? Most of our knowledge has been gained through a deliberate simplification of the reacting system and through a strict control of the conditions of the reaction. Furthermore our knowledge is to a large extent indirect and based upon a detailed analysis of the initial conditions as well as of the results of the reaction event. A reader of detective novels would perhaps like to make a parallell to the concept of “circumstantial evidence” as a means to prove the guilt of a suspect.

The problem facing the scientist has been compared with that of a spectator of a drastically shortened version of a classical drama – “Hamlet” say – where he or she is only shown the opening scenes of the first act and the last scene of the finale. The main characters are introduced, then the curtain falls for change of scenery and as it rises again we see on the scene floor a considerable number of “dead” bodies and a few survivors. Not an easy task for the inexperienced to unravel what actually took place in between.

This year’s Nobel prize winners of chemistry have through their brilliant work in a decisive way enlarged our knowledge of the detailed events in chemical reactions. Reactions between molecules have been studied at low pressures by letting beams of molecules and/or atoms meet at one point in space. The energy of the reacting molecules or atoms has been controlled and the properties of the products formed – their chemical composition, their angular distribution from the place of collision, their speed and their rotational and vibrational energy – have been studied. Through experiments of this kind the prizewinners of this year have been able to paint a very detailed picture of the molecular drama occurring between the opening scene and the finale.

Many of the results obtained have been unexpected and surprising and constitute a rich source of fundamental data for theoreticians to ponder. Their scientific work is truly pure basic chemical research of utmost quality but is nevertheless also of immediate importance for a number of other areas – from basic combustion research to chemistry in the stratosphere and troposphere – areas that are of great concern to mankind.

Professor Herschbach, Professor Lee and Professor Polanyi. Your brilliant research into the finer molecular details of chemical reactions has greatly advanced our knowledge in this central area of chemistry. Your approaches to the problem have differed in detail but your goals have been the same. You have, in a way that is truly admirable, combined extraordinary experimental skill with deep theoretical insight. In recognition of your services to chemistry and to natural science as a whole the Royal Academy of Sciences has decided to confer upon you this years Nobel Prize for Chemistry.

Professor Herschbach, Professor Lee and Professor Polanyi,

To me has been granted the privilege to convey to you the warmest congratulations of the Academy and I now invite you to receive your prize from the hands of His Majesty the King.