http://hdl.handle.net/2328/25737 2013-06-19T20:44:32Z http://hdl.handle.net/2328/26786 Title: Spectroscopic observation of gold-dicarbide: photodetachment and velocity map imaging of the AuC2 anion Authors: Visser, Bradley; Addicoat, Matthew A; Gascooke, Jason; Lawrance, Warren Donald; Metha, Gregory Francis Abstract: Photoelectron spectra following photodetachment of the gold dicarbide anion, AuC− 2 , have been recorded using the velocity map imaging technique at several excitation wavelengths. The binding energy spectra show well-defined vibrational structure which, with the aid of computational calculations and Franck-Condon simulations, was assigned to a progression in the Au–C stretching mode, ν3. The experimental data indicate that the features in the spectrum correspond to a 2A ←3A transition, involving states which we calculate to have bond angles ∼147◦ but with a low barrier to linearity. 2013-05-07T00:00:00Z http://hdl.handle.net/2328/26683 Title: Methyl rotor dependent vibrational interactions in toluene Authors: Gascooke, Jason; Lawrance, Warren Donald Abstract: The methyl rotor dependence of a three state Fermi resonance in S1 toluene at ∼460 cm−1 has been investigated using two-dimensional laser induced fluorescence. An earlier time-resolved study has shown the Fermi resonance levels to have different energy spacings at the two lowest methyl rotor states, m = 0 and 1. The overlapped m = 0 and 1 spectral features have been separated to provide direct spectral evidence for the m dependence of the resonance. The resonance has been probed at m = 3a″1 for the first time and found to be absent, providing further evidence for a large change in the interaction with m. Deperturbing the resonance at m = 0 and 1 reveals that the m dependence arises through differences in the separations of the “zero-order,” locally coupled states. It is shown that this is the result of the local “zero-order” states being perturbed by long-range torsion-vibration coupling that shifts their energy by small amounts. The m dependence of the shifts arises from the Δm = ±3n (n = 1, 2, …) coupling selection rule associated with torsion-rotation coupling in combination with the m2 scaling of the rotor energies, which changes the ΔE for the interaction for each m. There is also an increase in the number of states that can couple to m = 1 compared with m = 0. Consideration of the magnitude of reported torsion-rotation coupling constants suggests that this effect is likely to be pervasive in molecules with methyl rotors. 2013-04-02T00:00:00Z http://hdl.handle.net/2328/26647 Title: Understanding seawater intrusion. [Poster] Authors: Werner, Adrian D; Jacobsen, Peta E; Morgan, Leanne K Abstract: Seawater intrusion is the landward advance of seawater into freshwater aquifers, involving complicated density-dependent flow and salt transport process that are challenging to characterise and manage. Seawater intrusion is most induced by groundwater pumping, but can also occur from sea-level rise, changes in long-term recharge rates, seawater overtopping (e.g. due to tsunamis), and land-use activities such as canal developments. The widespread occurrence of seawater intrusion in coastal aquifers globally requires an elementary explanation of this complex phenomenon, to provide a framework for understanding and discussion amongst water resource managers, scientists, students, and others interested in the topic of coastal groundwater sustainability. This poster aims to address this by using coastal aquifer conceptual models to explain the complex nature of seawater intrusion, and to highlight a range of related issues, which include causal factors, ocean-groundwater interactions (e.g. tidal effects), methods of investigation, and management techniques. 2013-03-12T00:00:00Z http://hdl.handle.net/2328/26641 Title: The toluene-Ar complex: S0 and S1 van der Waals modes, changes to methyl rotation, and torsion-van der Waals vibration coupling Authors: Gascooke, Jason; Lawrance, Warren Donald Abstract: The methyl rotor and van der Waals vibrational levels in the S1 and S0 states of toluene-Ar have been investigated by the technique of two-dimensional laser induced fluorescence (2D-LIF). The S0 van der Waals and methyl rotor levels are reported for the first time, while improved S1 values are presented. The correlations seen in the 2D-LIF images between the S0 and S1 states lead to a reassignment of key features in the S1 ← S0 excitation spectrum. This reassignment reveals that there are significant changes in the methyl rotor levels in the complex compared with those in bare toluene, particularly at low m. The observed rotor energies are explained by the introduction of a three-fold, V3, term in the torsion potential (this term is zero in toluene) and a reduction in the height of the six-fold, V6, barriers in S0 and S1 from their values in bare toluene. The V3 term is larger in magnitude than the V6 term in both S0 and S1. The constants determined are |V3(S1)| = 33.4 ± 1.0 cm−1, |V3(S0)| = 20.0 ± 1.0 cm−1, V6(S1) = −10.7 ± 1.0 cm−1, and V6(S0) = −1.7 ± 1.0 cm−1. The methyl rotor is also found to couple with van der Waals vibration; specifically, the m″ = 2 rotor state couples with the combination level involving one quantum of the long axis bend and m″ = 1. The coupling constant is determined to be 1.9 cm−1, which is small compared with the values typically reported for torsion-vibration coupling involving ring modes. 2013-02-25T00:00:00Z