Absolute frequency measurements, with uncertainties as low as 2 kHz (1×10<sup>−11</sup>), are presented for the ν1+ν3 band of <sup>12</sup>C2H2 at 1.5 μm (194-198 THz). The measurements were made using cavity-enhanced, diode-laser-based saturation spectroscopy. With one laser system stabilized to the P(16) line of <sup>13</sup>C2H2 and a system stabilized to the line in <sup>12</sup>C2H2 whose frequency was to be determined, a Cr:YAG laser-based frequency comb was employed to measure the frequency intervals. The systematic uncertainty is notably reduced relative to that of previous studies, and the region of measured lines has been extended. Improved molecular constants are obtained.
© 2006 Optical Society of America
Original Manuscript: April 14, 2006
Revised Manuscript: June 6, 2006
Manuscript Accepted: June 8, 2006
Alan A. Madej, A. John Alcock, Andrzej Czajkowski, John E. Bernard, and Sergei Chepurov, "Accurate absolute reference frequencies from 1511 to 1545 nm of the ν1+ν3 band of 12C2H2 determined with laser frequency comb interval measurements," J. Opt. Soc. Am. B 23, 2200-2208 (2006)