Dye laser and diode laser spectroscopy of gas phase free radicals.
AdvisorBernath, Peter F.
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PublisherThe University of Arizona.
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AbstractThe gaseous free radicals, alkaline-earth metal monoalkylamides, monoacetylides, monoformamidates and monopyrrolidates, consisting of a metal atom (Ca or Sr) bonded to a single ligand, were synthesized in a Broida oven. The electronic and vibrational structures of these molecules were studied by low-resolution laser spectroscopy techniques. These inorganic molecules are ionic, well represented by the structure M⁺L⁻ (M = Ca, Sr: L = ligand). Three electronic transitions were identified for the metal monoalkylamides and the metal monoformamidates. The formamidate anion bonds to the metal in a bidentate fashion through the oxygen and nitrogen atoms. Two electronic transitions were observed for the metal monopyrrolidates. The pyrrolide anion ring bonds to the metal to provide these "open-faced sandwich" type molecules with pseudo-C₅ᵥ symmetry. For the metal monoacetylide molecules, only one electronic transition (Ā²Π-Ẋ²Σ⁺) was observed. Several vibrational frequencies were determined for these inorganic molecules from the low-resolution spectra. The Ā²Π-Ẋ²Σ⁺ transition of the calcium monoacetylide molecule was rotationally analyzed at high-resolution using the filtered laser excitation spectoscopy technique. The rotational line positions were fitted to a ²Π-²Σ⁺ Hamiltonian to obtain several rotational constants. The calcium-carbon bond length in CaCCH was calculated for the ground (2.248 Å) and excited (2.200 Å) electronic states. The vibration-rotation spectra of the gaseous bismuth hydride and bismuth deuteride molecules were recorded, using a diode laser system. The 1-0 fundamental band and several hot bands with Δv-1 were rotationally analyzed. The rotational line positions were fitted first, to a Dunham energy expression and then to a ³Σ⁻ Hamiltonian, to obtain ground state rotational constants. The bismuth-hydrogen (deuterium) bond distance was calculated to be 1.809 Å (1.807 Å).