Frequency metrology of the acetylene lines near 789Â nm from lamb-dip measurements

Lamb-dips of the ro-vibrational lines of 12C2H2 near 789 nm were recorded using cavity ring-down saturation spectroscopy. Calibrated by an optical frequency comb, frequencies of 45 acetylene lines were determined with an accuracy of 1.1×10−7 cm−1 (δν/ν=8×10−12), which is over two orders of magnitude more accurate than previous Doppler-limited studies. An averaged shift of about 0.01 cm−1 were found by comparing the upper energies obtained in this work to those recently presented by Chubb et al. from a MARVEL analysis.