Knowledge Bank

Understanding intermolecular interactions involving open shell systems is important to both combustion and atmospheric research. In this talk, we present microwave spectra of O$2$--HF and O$2$--DF, and analysis of their hyperfine structure. Last year, spectra were reported}$ Symposium on Molecular Spectroscopy} {\bf TE08} (2006)} for six different pure rotational transitions of O$2$--HF , though at the time, the analysis of the hyperfine structure was still incomplete. A simultaneous fit of microwave and infrared} {\bf117}, 693(2002)} data was also described. In this talk, we report a complete analysis of the hyperfine structure for O$2$--HF and a new global fit including microwave and infrared frequencies. New assignments for the $F1$ quantum numbers, together with complete assignment of $F$ quantum numbers has allowed all observed transitions of O$2$--HF to be fully analyzed with confidence. Calculated spectral intensities are also consistent with experimental observation. The Fermi contact parameters for the two nuclei are found to have opposite signs, consistent with a simple model based on spin polarization. Progress on analysis of magnetic and nuclear quadrupole hyperfine structure in O$2$--DF and global fit with IR data will be reported. The derived hyperfine parameters unambiguously establish the correspondence between the magnetic hyperfine constants and the two nuclei of the H(D)F.