The rotational spectrum of 17O2 up to the THz region

The investigation of the pure rotational spectrum of the (17)O2 isotopic species of molecular oxygen has been extended with respect to previous investigations to the submillimeter- wave region, from 230 GHz up to 1.06 THz. The resulting spectroscopic parameters, which have an accuracy comparable to that of the constants obtained from an updated isotopic invariant fit involving data for three electronic states and six isotopologues [Yu et al. High resolution spectral analysis of oxygen. IV. Energy levels, partition sums, band constants, RKR potentials, Franck–Condon factors involving the X 3Σg−, a 1Δg, and b1Σg+ states. J Chem Phys 2014; 141: 174302/1–12], permit the prediction of the pure rotational transitions up to 2 THz with an estimated uncertainty not greater than 100kHz. In the present study, high-level quantum-chemical calculations guided, supported, and complemented the determination of the hyperfine parameters of (17)O, with particular effort made in determining an accurate and reliable experimental value for the nuclear spin–rotation constant. A detailed discussion about the magnitude of the nuclear spin–rotation constant in the (17)O-containing O2 species for both the ground and the first excited electronic state is presented.