http://hdl.handle.net/2328/2961 Fri, 03 May 2013 08:33:17 GMT 2013-05-03T08:33:17Z 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. Tue, 02 Apr 2013 00:00:00 GMT http://hdl.handle.net/2328/26683 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. Tue, 12 Mar 2013 00:00:00 GMT http://hdl.handle.net/2328/26647 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. Mon, 25 Feb 2013 00:00:00 GMT http://hdl.handle.net/2328/26641 2013-02-25T00:00:00Z http://hdl.handle.net/2328/26640 Title: Total, elastic, and inelastic cross sections for positron and electron collisions with tetrahydrofuran Authors: Chiari, Luca; Anderson, Emma; Tattersall, Wade; Machacek, J R; Palihawadana, Prasanga; Makochekanwa, Casten; Sullivan, James; Garcia, Gustavo; Blanco, Francisco; McEachran, R P; Brunger, Michael James; Buckman, Stephen J Abstract: We present total, elastic, and inelastic cross sections for positron and electron scattering from tetrahydrofuran (THF) in the energy range between 1 and 5000 eV. Total cross sections (TCS), positronium formation cross sections, the summed inelastic integral cross sections (ICS) for electronic excitations and direct ionization, as well as elastic differential cross sections (DCS) at selected incident energies, have been measured for positron collisions with THF. The positron beam used to carry out these experiments had an energy resolution in the range 40–100 meV (full-width at half-maximum). We also present TCS results for positron and electron scattering from THF computed within the independent atom model using the screening corrected additivity rule approach. In addition, we calculated positron-impact elastic DCS and the sum over all inelastic ICS (except rotations and vibrations). While our integral and differential positron cross sections are the first of their kind, we compare our TCS with previous literature values for this species. We also provide a comparison between positron and electron-impact cross sections, in order to uncover any differences or similarities in the scattering dynamics with these two different projectiles. Fri, 15 Feb 2013 00:00:00 GMT http://hdl.handle.net/2328/26640 2013-02-15T00:00:00Z