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Absorption Spectroscopy, the Beer-Lambert Law, and Transition Polarizations

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Encyclopedia of Biophysics

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Synonyms

Absorbance of light; Transmission of light

Definition

Absorption can be pictorially viewed as either the electric field or the magnetic field (or both) of the radiation pushing the molecular electron density from a starting arrangement to a higher-energy final one (Atkins and de Paula 2006; Atkins and Friedman 2005; Hollas 2004). The electric field is far more effective than the magnetic field in achieving the push that gets a photon absorbed. The direction of net linear displacement of charge is known as the polarization of the transition. The polarization and intensity of a transition are summarized by its electric dipole transition moment, which is a vectorial property having a well-defined direction (the transition polarization) within each molecule and a well-defined length (which is proportional to the square root of the absorbance). The transition moment may be regarded as an antenna by which the molecule absorbs light. Each transition thus has its own antenna, and the...

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References

  • Atkins PW, de Paula J (2006) Physical chemistry. Oxford University Press, Oxford

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  • Atkins PW, Friedman RS (2005) Molecular quantum mechanics. Oxford University Press, Oxford

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  • Craig DP, Thirunamachandran T (1984) Molecular quantum electrodynamics: an introduction to radiation-molecule interactions. Academic, London

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  • Hollas JM (2004) Modern spectroscopy, 4th edn. Wiley, Chichester

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  • Tokmakoff A (2009) Introductory quantum mechanics II. In: Tokmakoff A, L. C. C. B.-N.-S. (ed) Massachusetts Institute of Technology: MIT OpenCourseWare. MIT, Boston. https://ocw.mit.edu

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Author information

Authors and Affiliations

  1. Department of Molecular Sciences, Macquarie University, Macquarie Park, NSW, Australia

    Alison Rodger

Authors
  1. Alison Rodger
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Correspondence to Alison Rodger .

Editor information

Editors and Affiliations

  1. University Leicester MRC Centre, Leicester, UK

    Gordon Roberts

  2. Dept Biochemistry, University of Oxford, Oxford, UK

    Anthony Watts

Section Editor information

  1. Department of Molecular Sciences, Macquarie University, Macquarie Park, NSW, Australia

    Alison Rodger

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© 2018 European Biophysical Societies' Association (EBSA)

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Rodger, A. (2018). Absorption Spectroscopy, the Beer-Lambert Law, and Transition Polarizations. In: Roberts, G., Watts, A. (eds) Encyclopedia of Biophysics. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-35943-9_782-1

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  • DOI: https://doi.org/10.1007/978-3-642-35943-9_782-1

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  • Publisher Name: Springer, Berlin, Heidelberg

  • Print ISBN: 978-3-642-35943-9

  • Online ISBN: 978-3-642-35943-9

  • eBook Packages: Springer Reference Biomedicine and Life SciencesReference Module Biomedical and Life Sciences

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