Empirical energy levels and line lists of HD17O and HD18O from the analysis of far infrared absorption spectra

Five far infrared absorption spectra of water vapor highly enriched in 17O, 18O and deuterium (D) are analyzed. The Fourier transform spectra at room temperature were recorded at the SOLEIL synchrotron facility with a 151.75 m absorption pathlength. The 50–720 cm−1 studied spectral region corresponds to the rotational band. The combined line list of the five spectra counts more than 12 900 lines which were assigned to about 13 960 transitions of the nine stable water isotopologues (H2XO, HDXO, D2XO with X = 16, 17, and 18). Line centers are determined with a typical accuracy of 5 × 10−5 cm−1 for isolated lines. The strong isotopic enrichment combined with the large spectral coverage and the unprecedented sensitivity of the recordings allow for extending considerably previous literature data for the HD17O and HD18O minor isotopologues. For each of these two species, the set of transition frequencies is merged to literature sources to generate extensive sets of accurate empirical rotational-vibrational energies for the ground, (000), and first excited, (010), vibrational states. The comparison to the previous datasets from an International Union of Pure and Applied Chemistry task group illustrates a gain on the average energy accuracy by more than one order of magnitude. Based on these accurate energy levels, recommended lists of transitions are generated with a 10−25 cm/molecule intensity cut-off for the (000)–(000), and (010)–(010) rotational bands and the ν2 band for both HD17O and HD18O. For the microwave region (0–1.5 THz), more complete lists with an intensity cut-off lowered to 10−29 cm/molecule are provided.