Knowledge Bank

Last year we reported to IO rotational spectrum in vibrational levels up to v = 13 for the $X1\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 3/2$ state and to v= 9 for the $X2\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 1/2$ state. In comparison, previous studies of BrO were limited to v = 2 for $X1$ and v=1 for the $X2$ state. Using the DC discharge cell that was so effective for vibrational excitation of IO, measurements of BrO have now been extended up to v=8 and v=7 for the $X1$ and $X2$ states, respectively. Excited vibrational levels of CIO were not obtained with these methods, however good signal to noise at thermal populations allowed measurements for the v=2 levels of both the $X1$ and $X2$ states as well as $\mathrm{<mrow\; data-mjx-texclass="ORD">18</mrow>}O$ in natural abundance. The Hamiltonian of Brown, $et.al.a$ with explicit isotope dependencies for each parameter, has provided a set of mass and nuclear moment independent parameters for each of the halogen monoxide species. The electron spin-rotation constant, $\gamma$, and the centrifugal distortion of the spin-orbit splitting, $AD$ which are normally correlated, have been separately determined by the isotope dependence of their contributions to the spectrum. Interatomic potentials have been derived from the mass-independent parameters that are accurate up to the observed excitation energies for each molecule. Analyses of the fine-structure parameters indicate that these molecules are close to the single perturber limit. The hyperfine parameters will be compared with the literature $valuesb,c,d$ of the appropriate calculated relativistic radial integrals of the halogens.