The rotational spectra of D2(17)O and HD(17)O: accurate spectroscopic and hyperfine parameters.

The Lamb-dip technique was employed to resolve the hyperfine structure of the rotational lines of D2(17)O and HD(17)O. The high resolution of this technique allowed us to obtain the hyperfine parameters with high accuracy. The experimental determination was supported by highly accurate quantum-chemical calculations of the hyperfine parameters involved. The experimental spin-rotation constants of (17)O were used to evaluate the paramagnetic contribution to the nuclear magnetic shielding constants, whereas the diamagnetic contribution was accurately determined by means of CCSD(T) calculations. These steps are part of a well-tested procedure, which also involves the determination of vibrational and temperature corrections. The present study is part of a wider project which aims at establishing an alternative experimental absolute NMR scale for oxygen and which has been started with an analogous investigation on H2(17)O. Due to the lack of information on spectroscopic parameters, the rotational spectra of D2(17)O and HD(17)O were also investigated at Doppler-limited resolution, spanning a large frequency range: from the millimeter-wave region up to the THz frequency domain. The recorded transitions allowed to determine rotational and centrifugal-distortion constants to a good accuracy.