Resolving final states and populations

Scattering is the correlation of the velocity after the collision v with the initial velocity v. For elastic scattering the magnitude of the velocity does not change, only its direction does. Not so for molecular scattering where, as a result of the collision, the internal energy of the molecule(s) can change. 

E dictates the energy of the products and thereby imposes a relation between the products internal energy and their relative translational energy E y  

Next we consider the product distribution in velocity space. A sphere of radius with tile center of mass as the origin is the locus of the tips of the velocity vectors of all those KI molecules formed in a particular internal state (and hence given E, for all possible angles of scattering. Different KI internal states would each correspond to a sphere of different radius in velocity space. The one with the 

We can regard the spheres as providing a spherical polar coordinate representation of the final-state angular distribution. The radius (fixed for given is the 

Crossed-beam experiments naturally produce flux velocity-angle contour maps, which can be measured with considerable detail. Applications include a variety of atom-diatom reactions, ion-molecule reactions, complex mode reactions, diatom atom reactions, etc. Examples are to be found throughout the text. For the special case when the reaction is photoinitiated we return to this 

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