Absolute 12C16O2 transition frequencies at the kHz-level from 1.6 to 7.8 μm

Absolute transition frequencies were measured for a series of transitions in the (30013)<-(00001) near-infrared (CO2)-C-12-O-16 band. These measurements were referenced to a cesium atomic clock through the use of an optical frequency comb. Combined standard uncertainties as low as 18 kHz (6 x 10(-7) cm(-1)) were achieved. Importantly, deviations as large as 5 MHz were observed relative to the HITRAN 2008 database. These measurements were then included in a global fit of 416 CO2 mid-infrared and near-infrared measurements each of which was absolute. The resulting spectroscopic parameters provide a series of secondary frequency standards with kHz-level uncertainties across a wide frequency range and should significantly improve spectroscopic retrieval algorithms for space-based measurements of atmospheric CO2. Published by Elsevier Ltd.