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 J=32 to J=52 in the P 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, B0 and D0, of CO were calculated. A second, slightly less precise set of measurements over approximately the same range of J values was similarly reduced, and combined estimates of the constants were obtained. Using the resulting value of B0 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)