Sub-Doppler Heterodyne Frequency Measurements on Isotopic Species of Carbon Monoxide and Improved Frequencies for Secondary Standards near 60 THz
✍ Scribed by Michael H. Wappelhorst; Stephan Saupe; Burkhard Meyer; Thomas George; Wolfgang Urban; André Le Floch
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 137 KB
- Volume
- 181
- Category
- Article
- ISSN
- 0022-2852
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✦ Synopsis
We report a series of sub-Doppler frequency measurements on four isotopic species of carbon monoxide (CO). The observed rovibrational transitions in the electronic ground state X 1 S / of CO cover the infrared spectral region between 58.5 and 63.3 THz (1951 -2112 cm 01 ). The CO laser heterodyne spectrometer with optional microwave sideband generation utilizes heterodyne techniques to measure the frequency of a CO laser, which is locked to saturation signals of CO transitions at low pressure, against combination frequencies of two saturation-stabilized CO 2 lasers. Frequencies for ground state transitions of three isotopic species of CO are determined with very high accuracy, including the first heterodyne frequency measurements in the fundamental band of 13 C 18 O. A systematic correction (between 04 and 013 kHz) of our earlier published CO sub-Doppler frequencies became possible with the 1994 improvement of the CO 2 laser standard frequency values. The updated frequencies together with the new measurements exhibit absolute frequency uncertainties around 20 kHz (Dn/n É 3 1 10 010 ). They are the most accurate frequencies of CO ground state transitions suitable for secondary frequency standards and calibration of infrared spectrometers in the 60-THz spectral region.