The far-infrared spectrum of 18O enriched water vapour (40–700 cm−1)

Abstract

The rotational spectrum of water vapour highly enriched in 18 O has been studied by high resolution (≈ 0.001 cm -1 ) Fourier transform spectroscopy at the AILES beam line of the SOLEIL synchrotron. The room temperature absorption spectrum has been recorded between 40 and 700 cm -1 . The 18 O enrichment of the sample was about 97% while the gas pressure and the absorption pathlength were set to 0.97 mbar and 151.75 m, respectively. The spectrum contains more than 4800 rotational transitions from seven water isotopologues (H2 18 O, H2 16 O, H2 17 O, HD 18 O, HD 16 O, HD 17 O, D2 18 O). The assignments were performed using known experimental energy levels as well as calculated line lists based on the results of Schwenke and Partridge. The amount and accuracy of the reported line positions represent an important extension compared to previous works. Overall, lines of about 2570 transitions are observed for the first time and 35, 41, 50, and 16 new energy levels are determined for H2 18 O, H2 17 O, HD 18 O, and HD 17 O, respectively. The set of derived energy levels shows a number of important differences from those recommended by an IUPAC-task group. Compared to the HITRAN2016 database, numerous deviations of line positions (up to 0.15 cm -1 ) are found for the H2 17 O, H2 18 O, HD 17 O, and HD 18 O species. Incomplete and wrong HITRAN's assignments of more than 90 transitions for H2 18 O, H2 17 O and HD 18 O are identified. Overall, the measured line positions will allow to significantly refine and complete the sets of empirical energy levels of H2 18 O, H2 17 O, HD 18 O and HD 17 O in the ground vibrational state.

The W2020 Database of Validated Rovibrational Experimental Transitions and Empirical Energy Levels of Water Isotopologues. II. H217O and H218O with an Update to H216O

“…31, both by making the necessary adjustments indicated by comparisons with the 20MiKaMoCa 66 linelist and by the availability of new sources. 53,63,102,152,153 As is clear from Fig. 1, the updated W2020-H 2…”

“…O and H 2 18 O. In particular, the sources 01NaUbLePo, 102 17CaMiVaRe, 53 and 20MiBeOdTr, 63 containing dipole-allowed transitions, were added to the W2020-H 2 16 O dataset. 31 The sources 01NaUbLePo, 102 17CaMiVaRe, 53 and 20MiBeOdTr 63 O.…”

“…In particular, the sources 01NaUbLePo, 102 17CaMiVaRe, 53 and 20MiBeOdTr, 63 containing dipole-allowed transitions, were added to the W2020-H 2 16 O dataset. 31 The sources 01NaUbLePo, 102 17CaMiVaRe, 53 and 20MiBeOdTr 63 O. Due to the high quality of the assigned transitions in these three sources, 53,63,102 it proved to be straightforward to expand the xMARVEL input with these new entries without any relabeling or significant uncertainty adjustments.…”

“…31 The sources 01NaUbLePo, 102 17CaMiVaRe, 53 and 20MiBeOdTr 63 O. Due to the high quality of the assigned transitions in these three sources, 53,63,102 it proved to be straightforward to expand the xMARVEL input with these new entries without any relabeling or significant uncertainty adjustments. Furthermore, in 2020, two studies reporting weak, quadrupole-allowed transitions 152,153 O dataset can be found in the supplementary material.…”

“…O dataset 31 was updated with three relevant sources 53,63,102 to facilitate the subsequent analysis of the highresolution spectroscopic data of H 2 17 O and H 2 18 O. As part of this step, some of the labels in the original W2020-H 2 16 O dataset 31 were changed so that the dataset now mimics considerably better than before (and even supersedes) the limited SISAM 154 and 20MiKa-MoCa 66 linelists.…”