Molecular Beam Studies of Elementary Chemical Processes (Nobel Lecture)

Which internal degrees of freedom of a reactant influence the reaction probability and what consequences does this have on the course of elementary chemical processes? These questions, whose answers are very important for the understanding of reaction dynamics and for checking the predictions of quantum‐mechanical calculations, were addressed by the recipients of the 1986 Nobel Prize for Chemistry— Y. T. Lee, J. C. Polanyi , and D. Herschbach (his Nobel Lecture will appear in the December issue). They studied reactions by using the crossed molecular beam method or by measurement of IR chemiluminescence and were thereby able to determine the relative orientations of the reactants most favorable for a reactive collision, to prove some proposed reaction mechanisms to be invalid, to detect and interpret unexpectedly small activation energies, and to clarify the nature of the energy transfer between reactants and products.