Absolute frequency list of the v₃-band transitions of methane at a relative uncertainty level of 10^-11

We determine the absolute frequencies of 56 rotationvibration transitions of the v₃ band of CH₄ from 88.2 to 90.5 THz with a typical uncertainty of 2 kHz corresponding to a relative uncertainty of 2.2 × 10^-11 over an average time of a few hundred seconds. Saturated absorption lines are observed using a difference-frequency-generation source and a cavity-enhanced absorption cell, and the transition frequencies are measured with a fiber-laser-based optical frequency comb referenced to a rubidium atomic clock linked to the international atomic time. The determined value of the P(7) F₂⁽²⁾ line is consistent with the International Committee for Weights and Measures recommendation within the uncertainty.