Absolute frequencies of lasing transitions in seven CO2isotopic species

The band centers, rotational constants, absolute frequencies, and vacuum wavenumbers for¹²C¹⁶O2,¹³C¹⁶O2,¹²C¹⁸O2,¹³C¹⁸O2,¹²C¹⁶O¹⁸O,¹⁴C¹⁶O2, and¹⁴C¹⁸O2have been simultaneously computed from 590 beat frequency measurements between pairs of adjacent I and II band CO2laser transitions. The input data included the 56 beat frequencies measured between adjacent¹²C¹⁶O2rotational lines by Petersen et al. The absolute frequencies are directly related to the cesium frequency standard via the 29 442 483.315 (0.025) MHz 10.18 μm I-R (30) and the 32 134 266.891 (0.024) MHz 9.33 μm II-R(10) transitions in¹²C¹⁶O2which were measured by Evenson et al. The results described in this paper will provide the means for setting up easily reproducible secondary frequency standards in the m wavelength band.