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Magnetic Circular Dichroism (MCD) Spectroscopy

  1. John Mack,
  2. Martin J. Stillman

Published Online: 15 DEC 2011

DOI: 10.1002/9781119951438.eibc0289

Encyclopedia of Inorganic and Bioinorganic Chemistry

Encyclopedia of Inorganic and Bioinorganic Chemistry

How to Cite

Mack, J. and Stillman, M. J. 2011. Magnetic Circular Dichroism (MCD) Spectroscopy. Encyclopedia of Inorganic and Bioinorganic Chemistry. .

Author Information

  1. University of Western Ontario, London, ON, Canada

Publication History

  1. Published Online: 15 DEC 2011

Abstract

Magnetic circular dichroism (MCD) spectroscopy provides information about the spin and orbital angular momenta associated with ground and excited electronic states. This can provide the key to understanding the optical spectroscopy of high symmetry ions and complexes, which provides an important insight into the electronic structure. MCD spectra contain the same set of spectral bands as the corresponding electronic absorption spectrum, with significantly different band morphologies due to the effect of the applied magnetic field and the use of a differential absorbance intensity scale.

MCD spectra are recorded by mounting a superconducting magnet (B ≈ 0–11 T), an electromagnet (B ≈ 0–1 T), or a permanent magnet into the sample compartment of a CD spectrometer with the field applied parallel to the axis of light propagation. Parallel applied fields are often referred to as the Faraday magnet alignment, since it formed the basis of Faraday's pioneering experiments in which plane polarized beams of light were found to be rotated during transmission through certain substances, due to the differential absorbance of left circularly polarized (lcp) and right circularly polarized (rcp) light. The Faraday ��1, ℬ0, and ��0 terms form the basis for the analysis of MCD spectra based on the Zeeman splitting of the absorption bands for lcp and rcp light, the field-induced mixing of zero-field states, and the Zeeman splitting-based ground state population adjustment, respectively.

Keywords:

  • magnetic circular dichroism spectroscopy;
  • angular momentum;
  • paramagnetic molecules;
  • polarized light;
  • superconducting magnet;
  • porphyrins;
  • phthalocyanines;
  • heme proteins