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Triatomic Spectral Database

NIST Standard Reference Database 117

Last Update to Data Content: July 2003 | Version HistoryDisclaimer | DOI:

Frank J. Lovas, J. S. Coursey, S. A. Kotochigova, J. Chang, K. Olsen, and R. A. Dragoset
NIST Physical Measurement Laboratory

All of the rotational spectral lines observed and reported in the open literature for 55 triatomic molecules have been tabulated. The isotopic molecular species, assigned quantum numbers, observed frequency, estimated measurement uncertainty and reference are given for each transition reported. In addition to correcting a number of misprints and errors in the literature cited, the spectral lines for approximately 15 molecules have been refit to produce a comprehensive and consistent analysis of all the data extracted from various literature sources. Both measured and predicted transition frequencies are listed for several isotopic forms of HCN, H2O, H2S, and OCS. The derived molecular properties, such as rotational and centrifugal distortion constants, hyperfine structure constants, electric dipole moments, and rotational g-factors are listed with one standard deviation uncertainty for all values.

  1. Introduction
  2. General Description of the Tables
  3. Molecular Parameters and Energy Level Formulation
  4. Evaluation of the Spectral Data
  5. List of Symbols
  6. Special Units, Fundamental Constants, and Useful Conversion Factors
  7. Acknowledgments
  8. References to the Text
  9. Appendix 1. Molecular Structures of Triatomic Molecules
  10. Appendix 2. Discussion of Centrifugal Distortion Analysis of F2O

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See our other Molecular Spectral Databases: Diatomic | Hydrocarbon | Molecular Microwave Spectral


NIST Standard Reference Database 117
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Online: July 2002 | Last update: July 2003


These databases were funded [in part] by NIST's Standard Reference Data Program (SRDP) and by NIST's Systems Integration for Manufacturing Applications (SIMA) Program.



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Created September 12, 2009, Updated January 20, 2022