Angular distributions and vector correlations

The product state distributions and the populations of the various chemical and electronic channels belong to the category of so-called scalar properties which are defined without reference to a particular coordinate frame. They have a magnitude but no direction. However, since the electromagnetic field vector E of the photolysis laser defines a specific direction in the laboratory frame, all vectors inherent to a photodissociation process can be measured relative to E. The vectors of interest are  

1) The transition dipole moment function of the parent molecule, pi. 

The oldest known vector correlation is the angular distribution of the photofragments, i.e., the relation between the recoil velocity v and the polarization vector E, 

---