High resolution spectroscopy of some gaseous transition metal containing diatomic molecules
Creators: name: Huang, Gejian
Publisher: name: University of British Columbia
Year: 2008

description: This thesis reports studies of the electronic spectra of some gaseous diatomic molecules containing transition metals. The (0,0) bands of the C³Π - X³Δ, e¹Π - X³Δ and f¹Φ - a¹Δ electronic transitions of niobium nitride (NbN) have been recorded at sub-Doppler resolution by intermodulated laser-induced fluorescence. The C³Π and e¹Π states, which belong to the same electron configuration (4dδ)¹(4dπ)¹, interact strongly with each other by a second-order spin-orbit/Fermi contact mechanism; the structure of the resulting e¹Π/ C³Π complex has been treated by a full Hamiltonian matrix analysis, which resulted in a deperturbed set of spin and hyperfine parameters as well as interaction parameters. From the well resolved low J lines of the f¹Φ - a¹Δ (0, 0) band, the hyperfine parameters "a" were measured accurately for the ¹Δ and ¹Φ states; they were found to have been modified by the spin-orbit/Fermi contact cross terms &lt; a¹Δ | Ĥ | X³Δ &gt; and &lt; f¹Φ | Ĥ | B³Φ &gt; respectively. Wavelength-resolved fluorescence studies of the emission spectra from the laser-excited e¹Π and f¹Φ states located a new ¹Σ⁺ and a new ¹Γ electronic state at 5863 and 9919 cm⁻¹, respectively. The low energy of the ¹Σ⁺ state suggests that it arises from the electron configuration (5sσ)²; while the ¹Γ state can only come from the configuration (4dδ)². The vibrational sequence bands of the B - X and C - X systems, along with some weak sub-bands in the region 18200 - 18500 cm⁻¹, have been rotationally analyzed from the laser excitation spectra of NbN. Two of the weak sub-bands were assigned as vibrational bands of the transition (5sσ)¹(4dπ)¹ Y³Π₂ - X³Δ₃, from preliminary analysis of the hyperfine structure; the other weak sub-bands were found to originate from the X³Δ state and to have charge transfer upper states of Π symmetry with B constants of about 0.45 cm⁻¹. The B⁴Π - X⁴Σ⁻ (1,0) band of VO has been investigated at sub-Doppler resolution by intracavity laser-induced fluorescence spectroscopy and at Doppler-limited resolution by emission spectroscopy. Values of the principal hyperfine parameters "a" and (b + c) for the B⁴Π state have been deduced from the resolved hyperfine structures of the low J lines of the B⁴Π [5/2 subscript] - X and B⁴Π [3/2 subscript] - X sub-bands: a = 0.00964 cm⁻¹ and (b + c) = -0.01295 cm⁻¹. Estimates of the dipolar parameter c show that it is small compared to b, so that the Fermi contact parameter b is sizeable and negative; this allows the electron configuration of the B⁴Π state to be assigned as (3dδ)²(3dπ)¹. Rotational analysis of the emission spectra of the B⁴Π - X⁴Σ⁻ (1,0) band proved that the B⁴Π [1/2 subscript] (v = 1) substate is perturbed by an orbitally non-degenerate Σ state. The perturbing state has a fairly large rotational constant, B = 0.5405 cm⁻¹, and very large hyperfine structure; this suggests that it is the ²Σ⁺ state from the electron configuration (3dδ)²(4dσ)¹. A portion of the red system of CoO, from 6100 to 6450 Å, has been studied by intracavity laser-induced fluorescence spectroscopy. Hyperfine analysis of two ⁴Δ [7/2 subscript] - X⁴Δ [7/2 subscript] sub-bands and one ⁴Δ [5/2 subscript] - X⁴Δ [5/2 subscript] sub-band, with origins at 6338 Å, 6411 Å and 6436 Å, gave the principal hyperfine parameters "a" and (b + c) for the upper and lower states. From the derived Fermi contact parameters b, it was possible to assign the X⁴Δ state to the configuration (4sσ)²(3dδ)³(3dπ)², and the two excited ⁴Δ states to (4sσ)¹(3dδ)³(3dπ)²(3dσ)¹ and (O,2pπ)³(4sσ)²(3dδ)³(3dπ)³. The spin structure of the X⁴Δ ground state of CoO was measured directly by wavelength-resolved fluorescence with the observation of spin satellites from the excited ⁴Δ [7/2 subscript] and ⁴Δ [5/2 subscript ] levels. Values of the first- and second-order spin-orbit coupling constants A and λ for X⁴Δ have been deduced from the sub-state origins: A = 166.2 cm⁻¹ and λ = 7.32 cm⁻¹. Rotational analysis of 16 other sub-bands of the red system of CoO revealed a very complex upper state energy level structure with extensive global and local perturbations. Vibrational levels belonging to various ⁴Δ, ⁴Φ and ⁴Π excited states have been partially identified.