Bond lengths coordinate systems

M and R are the equilibrium dipole moment and bond length of C-X bond and p and r are the respective quantities for the C-Hi bond. Local coordinate systems are shown in Fig. 5.1 (Reproduced from Ref [151] with permission). 

At this point, it is wise to see an example, and I will take H2O with a bond length of 95.6 pm and bond angle of 104.5°. If I take the coordinate system such that the molecule lies in the yz-plane with coordinate origin given by the centre of mass, and the z-axis as the symmetry axis, then the Cartesian coordinates are given in Table 8.4. 

The EXAFS, which occurs at higher energies above the edge, is due to the interference between the outgoing and the backscattered photoelectron waves (10-14). EXAFS provides information about the local structure of the x-ray absorbing atom. Typically, nearest neighbor bond lengths and coordination numbers can be determined to 0.02 A (1%) and one atom in four (25%) (4 ). The accuracy of these determinations is somewhat worse for outer-shell atoms, for disordered systems, or for systems with asymmetric distributions of atoms within a shell (15,16). 

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