  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 1,3e-10 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 fourtyfold improvement in the
line centers' resolution compared to the previous result.
