Spectroscopy of the formaldehyde isotopomer H213CO in the microwave to terahertz region

The pure rotational spectrum of H213CO in its ground vibrational state has been investigated extensively between 8 and 1900 GHz using samples of natural isotopic abundance as well as samples enriched in 13C. The accurate new line frequencies were subjected to a combined fit with previously published data, resulting in distinctly improved spectroscopic constants, which include several octic and one decic centrifugal distortion constants. Fits employing Watson's S and A reductions will be compared. The following rotational constants have been obtained: AS=281993.0397 (31), BS=37809.106966 (213), CS=33215.941417 (207) and AA=281993.0148 (32), BA=37811.090040 (219), CA=33213.976745 (207) MHz, respectively.