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Group Theory for High-resolution Spectroscopy of Nonrigid Molecules

  1. Melanie Schnell

Published Online: 15 SEP 2011

DOI: 10.1002/9780470749593.hrs073

Handbook of High-resolution Spectroscopy

Handbook of High-resolution Spectroscopy

How to Cite

Schnell, M. 2011. Group Theory for High-resolution Spectroscopy of Nonrigid Molecules. Handbook of High-resolution Spectroscopy. .

Author Information

  1. Fritz-Haber-Institut der MPG, Berlin, Germany

Publication History

  1. Published Online: 15 SEP 2011


Nonrigid molecules are an important molecule class and very intriguing to study. Already small molecules such as ammonia or Na3 are known to be nonrigid. With increasing size, however, several large-amplitude motions are possible in a molecule, which can even interact with one other. The molecular high-resolution spectra of nonrigid molecules are known to be quite complicated and very rich in information. Details about the molecule and its internal dynamics, such as the molecular structure, the character of the chemical bonds as well as the barrier heights to internal rotation and their dependence on the chemical bonds can be extracted. However, because of the nonrigidity of the molecule and the complexity of such spectra, their analysis is usually quite challenging. Theoretical methods are needed for their prediction and analysis. This article concentrates on permutation-inversion group theory and its usefulness in the analysis of high-resolution spectra of nonrigid molecules, which is examined in more detail using different examples.


  • high-resolution spectroscopy;
  • microwave spectroscopy;
  • group theory;
  • internal rotation;
  • local-mode theory;
  • Stark effect;
  • quadrupole coupling;
  • nonrigid molecules