Magnetic Circular Dichroism (MCD)

Ok, so this week in bio inorganic, I was assigned Magnetic Circular Dichroism to research and give a short synopsis of in class. MCD "measures the difference in electronic absorption of left and right circularly polarized light in a longitudinal magnetic field." What I understood this to mean was that a sample was placed in a magnetic field and then hit with circularly polarized light and then I got lost. I'm not exactly sure what happens when the light hits the sample and what exactly the detectors pick up, so any info on that would be greatly appreciated. I did however learn that MCD is very useful in determining the metal center oxidation state and spin state in a complex ion. Also, MCD gives electronic excited state properties and assignments and ground state magnetic properties (g-values, spin state, zero-field splittings, and magnetic couplings). Some of the limitations of MCD are that detailed electronic assignments are difficult for low-symmetry metal centers, or that it is not useful for investigating non-chromophoric (without color) metal centers. That was kind of the quick intro to MCD, so some parts may be confusing. Feel free to leave questions or info to help clarify my confusion. Thanks

-The High School Chemist