B Appendix The quantitative representation of flux contour maps

B Appendix The quantitative representation of flux contour maps 

Retnming to our KI example, consider the total number of molecules scattered per unit time into a solid angle A co with final translational energy in the range 

As previously, e.g., Eq. (3.5), we define the cross-section through the rate. Here, as in Eq. (4.48), it is the rate of reactive collisions with products scattered into a narrow range in both energy and direction. 7k is the flux of K atoms and ni, is the number of I2 molecules. We write the element of a solid angle d m as a lenunder that it is a double differential, d u = d cos 9 A p. 

The differential cross-section defined by (B.6.1) is related to the state-resolved differential cross-section as follows. First we go over from discrete final internal state indices to a continuous translational energy variable 

The usual flux velocity-angle contour map is of this quantity in a (0, ) polar coordinate system. Experimentally, it is easier to determine the relative values of the cross-section for different velocities. The results are then presented as a distribution P(6,u ) a a(9,u ) that can be normalized by integration over aU scattering angles and velocities,/du f d oE P(6, u )= 1. 

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