Accurate optical frequency atlas of the 1.5-µm bands of acetylene

We have measured the absolute optical frequencies of 90 rovibrational lines of the 12C2H2 and 13C2H2 1.5-µm bands. Using an optical frequency comb generator, we could precisely measure the relative frequencies between two lasers stabilized on the saturation dip of the rovibrational lines up to 2 THz apart. The absolute frequencies were determined with respect to the Rb two-photon transition at 0.778 µm with a HCN rovibration line at 1.556 µm used as an intermediate reference. This measurement provides an accurate frequency atlas of acetylene 1.5-µm bands with an uncertainty of ∼10-9.