Photofragments angular velocity distribution

Figure 9.10 Exampleofion-velodtymappingofproducts in a photofragmentation experiment. Top photofragment recoil for molecular transitions with fi parallel or perpendicular to the laser field polarization E, and subsequent extraction of ionized fragments. Middle inverse Abel-transformed image of the velocity distribution of ionized D atoms produced in the photolysis of DI at A = 205 nm. Bottom angular and velodty distributions extracted from the ion image map for the D -EI and D -E I fragmentation channels. Data adapted from McDonnell and Heck J. Mass Spectrom., 1998, 33 415, with permission of John Wiley Sons Ltd...

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,... 

Figure 22.5 shows a pictorial representation of the so-called two-vector correlation, both in photodissociation (half-collisions) and in atom-exchange reactions (full collisions). The important point to consider is that photodissociation is an anisotropic process in which the polarization of the electric field Sp of the photolysis laser defines a direction with respect to which the vector describing both products and parent molecule can be correlated. As a consequence, one can measure and analyse the correlation between the parent transition dipole moment fi and the recoil photofragment velocity vector, i.e. the v correlation. Thus, the angular distribution of the photofragments I 6) can be described in the form (Zare, 1972)... 

The angular distribution of photofragments depends particularly on the symmetry of the electronic transition and the direction of the photol) is laser polarization vector. The angular distribution of photofragments is usually described by the anisotropy parameter / . In particular, the recoil distribution, which is related to the velocity of the fragment v and the polarization vector of the electromagnetic field E, is given by... 

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