Accurate frequencies of molecular transitions used in laser stabilization: the 3.39-μm transition in CH4 and the 9.33- and 10.18-μm transitions in CO2

Abstract

The frequencies of three lasers stabilized to molecular absorptions were measured with an infrared‐frequency synthesis chain extending upwards from the cesium frequency standard. The measured values are 29.442 483 315 (25) THz for the 10.18‐μm R(30) transition in CO₂, 32.134 266 891 (24) THz for the 9.33‐μm R(10) transition in CO₂, and 88.376 181 627 (50) THz for the 3.39‐μm P(7) transition in CH₄. The frequency of methane, when multiplied by the measured wavelength reported in the following letter, yields 299 792 456.2(1.1) m/sec for the speed of light.