What did the chemists see as the time resolution was successively improved? The first success  was the discovery of substances formed along the way from the original one to the final product,  substances termed intermediates. To begin with these were relatively stable molecules or  molecule fragments. Each improvement of the time resolution led to new links in a reaction chain,  in the form of increasingly short-lived intermediates, being fitted into the puzzle of understanding how the reaction mechanism worked. 

This new branch of science, Femto Second was discovered in 1988,following extensive research at the Caltech University, California, USA.This discovery will be used extensively in the other disciplines, such as medicine, electronics, material and space science, among others. 

The contribution for which Zewail is to receive the Nobel Prize means that we have reached the end of the road: no chemical reactions take place faster than this. With femtosecond spectroscopy  we can for the first time observe in 'slow motion' what happens as the reaction barrier is crossed  and hence also understand the mechanistic background to Arrhenius' formula for temperature dependence and to the formula  for which van't Hoff was awarded his Nobel Prize. 

Femtosecond studies following Zewail's work are being performed intensively the world over,  using not only molecular beams but also processes on surfaces (e.g. to understand and improve  catalysts), in liquids and solvents (to understand mechanisms of the dissolving of and reactions  between substances in solution) and in polymers (e.g. to develop new material for use in  electronics). Another important research field is studies of biological systems. Knowledge of the  mechanisms of chemical reactions is also important for our ability to control the reactions. A desired chemical reaction is often accompanied by a series of unwanted, competing reactions that  lead to a mixture of products and hence the need for separation and cleansing. If the reaction can be controlled by initiating reactivity in selected bonds, this could be avoided. 

Femtochemistry has fundamentally changed our view of chemical reactions. From a phenomenon described in relatively vague metaphors such as 'activation' and 'transition state', we can now see  the movements of individual atoms as we imagine them. They are no longer invisible. Here lies the  reason why the femtochemistry research initiated by this year's Nobel Laureate has led to explosive development. With the world's fastest camera available, only the imagination sets  bounds for new problems to tackle. 

Scientists the world over are studying processes with femtosecond spectroscopy in gases, in fluids  and in solids, on surfaces and in polymers. Applications range from how catalysts function and how molecular electronic components must be designed, to the most delicate mechanisms in life  processes and how the medicines of the future should be produced. 
 

probing will no doubt bring a new interpretation to such cherished concepts of chemistry as resonance, breaking and forming of chemical bonds, their energies, and their covalent or ionic nature. 

Zewail's technique, using what could be described as the world’s fastest camera, makes it possible to watch individual atoms during a chemical reaction in the same way that viewers can watch details of a football match in a slow-motion replay. 

The technique helps explain why certain chemical reactions take place but not others and why the speed and yield of those reactions depend on temperature.