01487nas a2200121   4500008004100000245014800041210006900189260000800258300001600266490000700282520101500289856006101304       2022                        eng d00aAbsolute frequencies of H13C14N hydrogen cyanide transitions in the 1.5-µm region with the saturated spectroscopy and a sub-kHz scanning laser0 aAbsolute frequencies of H13C14N hydrogen cyanide transitions in   cNov  a5704–57070 v473 a<p>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 knowledge, the molecular transitions' center frequencies of the H13C14N isotope in the range from 1526 nm to 1566 nm with 1.3&amp;\#x00A0;×&amp;\#x00A0;10\textminus10 fractional uncertainty. We investigated the molecular transitions with a highly coherent and widely tunable scanning laser that was precisely referenced to a hydrogen maser through an optical frequency comb. We demonstrated an approach to stabilize the operational conditions needed to maintain the constantly low pressure of the hydrogen cyanide to carry out the saturated spectroscopy with the third-harmonic synchronous demodulation. We demonstrated approximately a forty-fold improvement in the line centers' resolution compared to the previous result.</p>  uhttps://opg.optica.org/ol/abstract.cfm?URI=ol-47-21-5704