Interferometric wavelength measurements have been made on thirty-three lines of the 2-0 band of CO at 4260 cm-1. These measurements were made relative to R(18) of this band, which had previously been measured against the Hg198 green line, and have a relative accuracy of I part in 107. The R(6) line of the 3-0 band has also been measured interferometrically. These data, when combined with results of other investigators, give the following values for constants, all in cm-1: B0= 1.922521+0.0000035 D0= 6.117×10-6+0.01×10-6D2-D0= -0.035008 D2-D0= -1.9×10-9B6= 1.931285 αe= 0.017535 γe= 1.01×10-5 βe= -1.0×10-9 ωe= 2169.829 xeωe= 13.295 yeωe= 0.0115.
The precise constants allow wavelengths to be calculated for the 1-0 band at 2143 cm-1. Since accurate measurements in this region are difficult to make, it is felt that these calculated values are more accurate than any measured values so far reported.
The value of B0, when combined with recent microwave results, gives for the velocity of light c=299 793.7± km/sec.
D. H. RANK, A. H. GUENTHER, G. D. SAKSENA, J. N. SHEARER, and T. A. WIGGINS, "Tertiary Interferometric Wavelength Standards from Measurements on Lines of the 2-0 Band of Carbon Monoxide and Derived Wavelength Standards for Some Lines of the 1-0 Band of Carbon Monoxide. The Velocity of Light Derived from a Band Spectrum Method. IV," J. Opt. Soc. Am. 47, 686-689 (1957)