Absolute frequencies of H13C14N hydrogen cyanide transitions in the 1.5-µm region with the saturated spectroscopy and a sub-kHz scanning laser

The wide span and high density of lines in its rovibrational spectrum render hydrogen cyanide a useful spectroscopic media for referencing absolute frequencies of lasers in optical communication and dimensional metrology. We determined, for the first time to the best of our knowl-edge, the molecular transitions' center frequencies of the H13C14N isotope in the range from 1526 nm to 1566 nm with 1.3 x 10-10 fractional uncertainty. We investigated the molec-ular transitions with a highly coherent and widely tunable scanning laser that was precisely referenced to a hydrogen maser through an optical frequency comb. We demon-strated an approach to stabilize the operational conditions needed to maintain the constantly low pressure of the hydro-gen cyanide to carry out the saturated spectroscopy with the third-harmonic synchronous demodulation. We demon-strated approximately a forty-fold improvement in the line centers' resolution compared to the previous result.