By infrared spectroscopy precise measurements of the wavelengths of forty-three rotational lines in the CO absorption band at 4.67 µ were made. Fifteen lines from <i>J</i>=32 to <i>J</i>=52 in the <i>P</i> branch were measured from the emission spectrum of CO. These data were reduced by the method of least squares, and values of the rotational constants, <i>B</i><sub>0</sub> and <i>D</i><sub>0</sub>, of CO were calculated. A second, slightly less precise set of measurements over approximately the same range of <i>J</i> values was similarly reduced, and combined estimates of the constants were obtained. Using the resulting value of <i>B</i><sub>0</sub> with the value obtained from microwave frequency measurements, the velocity of light was estimated to be 299 792 km/sec. The estimated standard deviation of this value is 6 km/sec.
EARE K. PLYLER, L. R. BLAINE, and W. S. CONNOR, "Velocity of Light from the Molecular Constants of Carbon Monoxide," J. Opt. Soc. Am. 45, 102-106 (1955)