Molecular Spectral Databases - Frequency Search Molecular Spectral Databases for Microwaves Main Page

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Frequency Search

You can limit your search to any of the the molecules listed. Note: Choosing "all molecules" results in a faster search than selecting each of the molecules individually. Warning: Excessively long searches may cause your browser to time out resulting in a message like "Document contains no data."

Frequency Range Search
You can search for a particular frequency range by using this field. If you use only the left text field, then your search will be for any frequencies greater than or equal to the frequency you enter. If you use only the right text field, then your search will be for any frequencies less than or equal to the frequency you enter. You can make your search in either megahertz or gigahertz. Most of the data is for the microwave region, however approximately 1% of the lines are radio waves and a few are infrared.

ASCII output
You can choose to have the output returned in ASCII format rather than an HTML table. The ASCII table is better for copying and pasting, but the HTML table looks better when printed.

Column Descriptions

To get the quantum numbers click the molecular species.

No more than 500 lines are displayed at a time. Additional lines are stored in a temporary file so that the lengthy search does not have to be repeated. You can click the link near the top of the page to get these lines. Note: They are only available for an hour, then the file is deleted.

Molecular Species
This is the molecular species to which the data pertains.

The observed transition frequency is given in megahertz.

The estimated uncertainty is also given in megahertz. Note: Since the maximum number of significant figures beyond the decmial point was fixed at three for the transition frequency and two for uncertainties, in a few cases it was necessary to round off the measured data. This situation occurs primarily in the reproduction of molecular beam measurements. When uncertainties were not given in the original source, an uncertainty was assigned on the basis of the internal consistency of all the data available for the molecule in question. In order to distinguish these from measured transitions, an asterisk (*) was placed in front of the estimated uncertainty, which is twice the standard deviation from the fit. If only an X appears, then it is to indicate that the uncertainty is unknown.

Refine Your Search

You can refine your search by changing the frequency range and/or the molecules searched. If you want to widen your search, you will need to start over by pressing the button at the bottom. Isotopic compositions data is provided so that you can determine which isotopes are most prevalent.

NIST Physical Measurement Laboratory Multiple Molecule Frequency Search Main Page National Institute of Standards and Technology NIST Physical Measurement Laboratory