text: One of the major goals of chemistry is the study of material transformations where chemical kinetics plays an important role. Scientists during the 19th century stated macroscopic chemical processes consist of many elementary chemical reactions that are themselves simply a series of encounters between atomic or molecular species. In order to understand the time dependence of chemical reactions, chemical kineticists have traditionally focused on sorting out all of the elementary chemical reactions involved in a macroscopic chemical process and determining their respective rates.
  Swedish chemist Svante Arrhenius studied this phenomenon during the late 1880s, and stated the relations between reactive molecular encounters and rates of reactions (formulated in terms of activation energies).
  Other scientists at the time also stated a chemical reaction is fundamentally a mechanical event, involving the rearrangement of atoms and molecules
  during a collision. Although these initial theoretical studies were only qualitative, they heralded a new era in the field of chemical kinetics; allowing the prediction of the dynamical course of a chemical reaction.
  In the 1950s, 1960s and 1970s, with the development of many sophisticated experimental techniques, it became possible to study the dynamics of elementary chemical reactions in the laboratory. Such as the analysis of the threshold operating conditions of a chemical laser or the spectra obtained using various linear or non-linear laser spectroscopic techniques.
  Professors Lees research focused on the possibility to control the energies of the reagents, and to understand the dependence of chemical reactivity on molecular orientation, among other studies related to the nature of reaction intermediates, decay dynamics, and identifying complex reaction mechanisms. To do so, Professor Lee used a breakthrough laboratory technique at the time, called the "crossed molecular beams technique", where the information derived from the measurements of angular and velocity distributions allowed him and his team to understand the dynamics of elementary chemical reactions.