Postulate of the activated molecular collision

Modem theories, if they retain the notion of an encounter between molecules, have profoundly changed the natnre of the meeting. We now call colhsion between two molecules, A and B, the establishment of energy interaction between these molecules over time. This interaction can have multiple consequences and thus lead to various phenomena, snch as the deviation of molecules from their initial trajectories, the transfer of energy from one molecule to another, breaking a bond in a molecule, the melting of the two molecules into one, etc. 

Consider an immobile molecule B surrounded by a gas of molecules A with a relative flow J. The efficient section g, of B for one of the previous phenomena is dJ. This is the number of encounter molecules A per unit of time and of area with a imit flux J and undergoes the shock with the concerned phenomena. We can see that Qi (the efficient section) has area units. In the given conditions, the value of the efficient section evidently depends on the phenomenon concerned. 

We will admit the following postulation as the basis of the modeling of elementary reactions. 

Postulation 10.1.- An elementary reaction between two molecules, A and B, requires a collision, in the sense given above to this term, between a molecule of A and a molecule of B. The colhsion mnst occur in the geometrical conditions (relative position between the two molecules) and at a given energy level. Under the effect of the colhsion, there is a redistribntion of energies within the molecules that leads to the final products of the reaction. 

The modehng of a reachon then appears like the evoluhon of a system made of nnclei and electrons of mass ntj over time. This evolution wih be entirely defined by the wave funchon O, which is the solution of the corresponding Schrddinger s eqnahon, in which Ep is the potential energy of the system and is written as  

---