Laser-induced fluorescence spectroscopy of cobalt monoboride and ruthenium monoboride

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University of New Brunswick
The electronic spectra of cobalt monoboride (CoB) and ruthenium monoboride (RuB) have been studied in the visible region of the electromagnetic spectrum. Both of these molecules have been previously studied by the Cheung group at medium resolution [1, 2]. In this thesis, the first high-resolution study performed on either molecule is reported. The previous spectroscopic study of CoB failed to resolve any hyperfine structure, and the work on RuB failed to resolve any of the ruthenium isotopes. The transition metal monoborides were produced in a laser ablation molecular jet apparatus and detected using laser-induced fluorescence (LIF) spectroscopy. Fine and hyperfine interaction parameters in the [18.3]3 (v′=2) and X³Δ₃ (v″=0) states of CoB have been determined from an analysis of the high-resolution LIF spectrum. In this thesis, updated rotational parameters for both states of CoB are reported, as well as hyperfine interaction parameters arising from the strong nuclear interaction of ⁵⁹Co (I=7/2, μ/μN = 4.627) with the magnetic fields produced by the molecule. Atomic hyperfine calculations have been conducted and support the X³Δ₃ ground state and indicate that the excited [18.3]3 state is formed from a mixing of configurations but the biggest contribution coming from a ³Δ₃ state. The (1, 0), (0, 0) and (0, 1) bands of the [18.4]2.5-X²Δ₅/₂ electronic transition of RuB have been taken with our high-resolution laser system. Ruthenium has seven naturally occurring isotopes ranging from 1.87% - 31.55% abundance and boron has two (¹¹B: 80.1% and ¹⁰B: 19.9%), giving a total combination of 14 isotopologues for RuB, of which we were able to isotopically analyze 12. Both of the odd isotopes of Ru have a nuclear spin I=5/2 and their respective isotopologues had resolved hyperfine structure which was analyzed to extract the hyperfine parameters. It was determined that the hyperfine interaction arises from the nuclear spin of the ¹⁰¹Ru and ⁹⁹Ru atoms and not from the boron nucleus. Atomic hyperfine calculations have also been conducted for RuB and help support the ground state symmetry, X²Δ₅/₂, and suggest that the likely contribution to the excited state is coming from a ²Φ₅/₂ state.