The hyperfine structure in the rotational spectra of D₂¹⁷O and HD¹⁷O: Confirmation of the absolute nuclear magnetic shielding scale for oxygen

Guided by theoretical predictions, the hyperfine structures of the rotational spectra of mono- and bideuterated-water containing ¹⁷O have been experimentally investigated. To reach sub-Doppler resolution, required to resolve the hyperfine structure due to deuterium quadrupole coupling as well as to spin-rotation (SR) and dipolar spin-spin couplings, the Lamb-dip technique has been employed. The experimental investigation and in particular, the spectral analysis have been supported by high-level quantum-chemical computations employing coupled-cluster techniques and, for the first time, a complete experimental determination of the hyperfine parameters involved was possible. The experimentally determined ¹⁷O spin-rotation constants of D₂¹⁷O and HD¹⁷O were used to derive the paramagnetic part of the corresponding nuclear magnetic shielding constants. Together with the computed diamagnetic contributions as well as the vibrational and temperature corrections, the latter constants have been employed to confirm the oxygen nuclear magnetic shielding scale, recently established on the basis of spin-rotation data for H₂¹⁷O [Puzzarini et al., J. Chem. Phys. 131, 234304 (2009)]