[2] Dual-energy computed tomography techniques take advantage of the increased attenuation of iodinated radiocontrast at lower tube energies to heighten the degree of contrast between iodinated radiocontrast and other high attenuation biological material present in the body such as blood and hemorrhage.
This dipole-forbidden transition gains intensity through a quadrupole mechanism and/or through 4p mixing into the final state.
The intensity under the pre-edge transition depends on the geometry around the absorbing metal and can be correlated to the structural symmetry in the molecule.
In the case of copper complexes, the rising-edge consists of intense transitions, which provide information about bonding.
[5] In the case of higher-oxidation-state copper atoms, the 1s→4p transition lies higher in energy, mixed in with the near-edge region.
The near-edge region is difficult to quantitatively analyze because it describes transitions to continuum levels that are still under the influence of the core potential.
Extraction of metrical parameters from the edge region can be obtained by using the multiple-scattering code implemented in the MXAN software.
[6] Ligand K-edge spectroscopy is a spectroscopic technique used to study the electronic structures of metal-ligand complexes.
[7] This method measures X-ray absorption caused by the excitation of ligand 1s electrons to unfilled p orbitals (principal quantum number
Transitions at energies lower than the edge can occur, provided they lead to orbitals with some ligand p character; these features are called pre-edges.
, the above expression relating intensity and quantum transition operators can be simplified to use experimental values: where n is the number of absorbing ligand atoms, h is the number of holes, and Is is the transition dipole integral which can be determined experimentally.
Therefore, by measuring the intensity of pre-edges, it is possible to experimentally determine the amount of ligand character in a molecular orbital.