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Observed Interstellar Molecular Microwave Transitions

NIST Standard Reference Database 116

Last Update to Data Content: September 2009 | Version HistoryDisclaimer | DOI:

NIST Recommended Rest Frequencies for Observed Interstellar Molecular Microwave Transition - 2009 Revision

Frank J. Lovas
Janet E. Bass, Robert A. Dragoset, Karen J. Olsen
NIST Physical Measurement Laboratory

© 1992, 1996, 2003, 2009 Copyright by the U.S. Secretary of Commerce on behalf of the United States of America. All rights reserved. NIST reserves the right to charge for these data in the future.


Critically evaluated transition frequencies for the molecular transitions detected in interstellar and circumstellar clouds are presented. The tabulated transition frequencies are recommended for reference in future astronomical observations in the centimeter and millimeter wavelength regions. The transition frequencies have been selected through a critical examination and analysis of the laboratory spectral data obtained from the literature. The information tabulated includes the species identity, transition frequency, uncertainty, and quantum state labels. For convenience, representative line antenna temperatures are listed for a typical astronomical source for each transition, and the references are cited for the laboratory and astronomical literature that have been employed.


  1. Introduction
  2. Source and Selection of Transition Frequencies
  3. Description of the Tables
  4. Acknowledgements
  5. References to Text
  6. References to Tables

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List of Tables

Table 1. Listing by empirical formula of the isotopic forms of the interstellar species in Table 4.
Table 2. Other species observed in comets, circumstellar and interstellar sources at IR and UV wavelengths, but not in Table 4.
Table 3. List of telescope abbreviations.
Table 4. Get Data and Search. Recommended rest frequencies for observed interstellar molecular lines. (Notes)


NIST Standard Reference Database 116
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Online: April 1996 - Last update: September 2009


Created September 15, 2009, Updated December 6, 2019