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Microwave Rotational Spectroscopy

  1. Yunjie Xu,
  2. Wolfgang Jäger

Published Online: 15 MAR 2008

DOI: 10.1002/0470862106.ia313

Encyclopedia of Inorganic Chemistry

Encyclopedia of Inorganic Chemistry

How to Cite

Xu, Y. and Jäger, W. 2008. Microwave Rotational Spectroscopy. Encyclopedia of Inorganic Chemistry. .

Author Information

  1. University of Alberta, Edmonton, AB, Canada

Publication History

  1. Published Online: 15 MAR 2008


Since its inception in 1934, microwave rotational spectroscopy has provided some of the most accurate data for numerous small to medium sized molecules, including structural parameters, force field parameters, and electronic charge distributions. We give a very brief review of the history of microwave spectroscopy, leading up to the most recent developments, that is, instruments that use Fourier transform techniques. Since these Fourier transform microwave spectrometers are not commercially available, a brief discussion about their general design is given. Analyses of the recorded rotational spectra can yield a number of spectroscopic parameters, depending on the molecular symmetry and the various angular momenta present, such as nuclear spins and electronic momenta. The physical significance of the more common spectroscopic parameters, such as rotational constants, centrifugal distortion constants, nuclear quadrupole coupling constants, etc. is given. We also indicate how these parameters can be used to characterize the molecule in terms of, for example, structural parameters, dynamical behavior, and bond character. The remainder of the article is devoted to case studies. These include the discovery of covalent bonds involving the noble gas atom argon, structural characterization of organometallic compounds, such as ferrocenes, bonding in diatomic transition metal-containing compounds, a description of laboratory studies of molecules which are of atmospheric and astrophysical interest, and studies of weakly bound complexes with relevance to inorganic chemistry.


  • microwave rotational spectroscopy;
  • Fourier transform spectroscopy;
  • molecular expansion;
  • laser ablation;
  • electric discharge;
  • rotational constants;
  • centrifugal distortion constants;
  • nuclear quadrupole coupling constants;
  • electric dipole moment;
  • molecular geometry and structure;
  • force field;
  • electron distribution