Terahertz spectroscopy of deuterated formaldehyde using a frequency multiplication chain

•Benchmarking terahertz source using molecular rotational spectra.•High accuracy measurements of rotational spectra of deuterated acetaldehydes.•Accurate frequency predictions for HDCO and D2CO above 1 THz.•Assignment and analysis of 13C, 17O, 18O and 13C18O substituted species in natural abundance.

The rotational spectra of deuterated formaldehyde HDCO and D2CO were recorded between 1.1 and 1.52 THz in order to benchmark new terahertz frequency multiplication chain used in the Lille spectrometer. Important spectrometer parameters such as sensitivity, measurement accuracy, and harmonic composition of the radiation source have been tested using the newly measured spectra. For each of the main deuterated isotopic species of formaldehyde the existent datasets from high resolution measurements were augmented by more than 300 new distinct transition frequencies. Most of these frequencies were measured with an accuracy better than 30 kHz. In addition, the high sensitivity of the spectrometer provided by the new frequency multiplication chain allowed observation, assignment and analysis of 13C, 17O, 18O, and 13C18O isotopic species of HDCO and D2CO. For some of these isotopologues the rotational parameters were determined for the first time.

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