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High resolution spectroscopy of some gaseous transition metal containing diatomic molecules

University of British Columbia

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 < a¹Δ | Ĥ | X³Δ > and < f¹Φ | Ĥ | B³Φ > 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.

Thesis/Dissertation

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2008-07-30

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http://hdl.handle.net/2429/1211

Chemistry

University of British Columbia

UBCV

DSpace