title: An estimation of the concentration of atmospheric nitrous oxide containing complexes

authors: Salmon, Steven Ray

abstract: Nitrous oxide (N₂O) is one of the major greenhouse gases responsible for climate change. It also has impacts on the removal of ozone (O₃) from the atmosphere and is now the single most important ozone depleting substance. Atmospheric N₂O primarily comes from bacterial denitrification processes in soils, a process which is augmented by many agricultural practices. As a result of the large amount of agricultural land in New Zealand, emissions of N₂O are disproportionately high for our population.
Nitrous oxide is primarily removed from the atmosphere via a photodissociation process, involving photons between 180 - 230 nm. The process of photodisociation involves the bending of the linear structure of the N₂O molecule, which allows for photodisociation to proceed. The presence of other gas molecules, such as those that we are investigating in our complexes, peturbs the bending mode of N₂O, which is throught to alter the photodisociation rate.
In this work we investigate the weakly bound complexes of N₂O with the major atmospheric molecules, namely N₂, O₂, Ar and H₂O. We use explicitly correlated coupled cluster theory to determine interaction energy, vibrational frequencies and rotational constants of the four complexes. This data is then used in combination with the standard statistical mechanics equations to determine the equilibrium constant of formation for each complex as a function of altitude. Finally the abundance profile of each complex is determined using the atmospheric concentrations of the constituent monomers.

text: An estimation of the concentration of atmospheric nitrous oxide containing complexes Nitrous oxide (N₂O) is one of the major greenhouse gases responsible for climate change. It also has impacts on the removal of ozone (O₃) from the atmosphere and is now the single most important ozone depleting substance. Atmospheric N₂O primarily comes from bacterial denitrification processes in soils, a process which is augmented by many agricultural practices. As a result of the large amount of agricultural land in New Zealand, emissions of N₂O are disproportionately high for our population.
Nitrous oxide is primarily removed from the atmosphere via a photodissociation process, involving photons between 180 - 230 nm. The process of photodisociation involves the bending of the linear structure of the N₂O molecule, which allows for photodisociation to proceed. The presence of other gas molecules, such as those that we are investigating in our complexes, peturbs the bending mode of N₂O, which is throught to alter the photodisociation rate.
In this work we investigate the weakly bound complexes of N₂O with the major atmospheric molecules, namely N₂, O₂, Ar and H₂O. We use explicitly correlated coupled cluster theory to determine interaction energy, vibrational frequencies and rotational constants of the four complexes. This data is then used in combination with the standard statistical mechanics equations to determine the equilibrium constant of formation for each complex as a function of altitude. Finally the abundance profile of each complex is determined using the atmospheric concentrations of the constituent monomers.

year: 2015

title: Generation and Langmuir probe analysis of a DC glow discharge and the deposition of chromium from a carbonyl precursor

authors: Pilling, L.S.

abstract: Experimental investigations detailed in this thesis fall into two distinct areas: Diagnostics of a nitrogen DC discharge with Langmuir probes and spectroscopy, and experiments designed to deposit chromium metal from a chromium hexacarbonyl precursor (Cr(C0)6). New diagnostic equipment was designed, tested and implemented to record Langmuir probe data with high resolution and accuracy. A monochromator was employed to record the light emission from the plasma. This identified which ionized species were present as well as the ion temperature from the resulting band structures present. The monochromator analysis was necessary to validate the assumptions of the Langmuir probe theory and to allow a choice of which theories applied. 
The Langmuir probe analysis of the recorded data for many plasmas have been well covered in the literature but few papers give a comprehensive coverage of the main probe theories using the one set of data and fewer still make use of double as well as single probes. The majority simply assume the particular theory used is relevant to the plasma conditions and the resulting temperatures and densities are correct. 
During the experiments and subsequent analysis it was found, similar to other researchers, that the ion densities were consistently higher than the electron densities even though the theoretical analysis applied in the saturation regimes appeared to be valid. Rather than ignoring this issue, and assuming ion collisions or secondary electron emission were the cause, new methods were developed to analyse the data. By determining the gradient of the saturation regimes and comparing them to those expected experimentally, it was found that the ion saturation regime neither followed the orbital nor radial motion theories investigated. However, the electron current did follow the orbital motion theory and it is demonstrated that the densities obtained from the ion currents, using these theories, were incorrect. This had been previously shown to be true only with non-probe methods. 
Using the same discharge configuration, impurity-free chromium films were deposited onto stainless steel substrates from a chromium hexacarbonyl precursor. This had been attempted by previous researchers, using a variety of discharge configurations, who invariably deposited similar metallic films with significant levels of oxygen and carbon impurities. The combination of the carbonyl precursor and the carrier gases (nitrogen and argon) with the discharge configuration resulted in these impurity-free films even when a negative bias of up to 50 V was applied to the sample.

text: Generation and Langmuir probe analysis of a DC glow discharge and the deposition of chromium from a carbonyl precursor Experimental investigations detailed in this thesis fall into two distinct areas: Diagnostics of a nitrogen DC discharge with Langmuir probes and spectroscopy, and experiments designed to deposit chromium metal from a chromium hexacarbonyl precursor (Cr(C0)6). New diagnostic equipment was designed, tested and implemented to record Langmuir probe data with high resolution and accuracy. A monochromator was employed to record the light emission from the plasma. This identified which ionized species were present as well as the ion temperature from the resulting band structures present. The monochromator analysis was necessary to validate the assumptions of the Langmuir probe theory and to allow a choice of which theories applied. 
The Langmuir probe analysis of the recorded data for many plasmas have been well covered in the literature but few papers give a comprehensive coverage of the main probe theories using the one set of data and fewer still make use of double as well as single probes. The majority simply assume the particular theory used is relevant to the plasma conditions and the resulting temperatures and densities are correct. 
During the experiments and subsequent analysis it was found, similar to other researchers, that the ion densities were consistently higher than the electron densities even though the theoretical analysis applied in the saturation regimes appeared to be valid. Rather than ignoring this issue, and assuming ion collisions or secondary electron emission were the cause, new methods were developed to analyse the data. By determining the gradient of the saturation regimes and comparing them to those expected experimentally, it was found that the ion saturation regime neither followed the orbital nor radial motion theories investigated. However, the electron current did follow the orbital motion theory and it is demonstrated that the densities obtained from the ion currents, using these theories, were incorrect. This had been previously shown to be true only with non-probe methods. 
Using the same discharge configuration, impurity-free chromium films were deposited onto stainless steel substrates from a chromium hexacarbonyl precursor. This had been attempted by previous researchers, using a variety of discharge configurations, who invariably deposited similar metallic films with significant levels of oxygen and carbon impurities. The combination of the carbonyl precursor and the carrier gases (nitrogen and argon) with the discharge configuration resulted in these impurity-free films even when a negative bias of up to 50 V was applied to the sample.

year: 2003

title: Tikanga Tainui: Tikanga whare wānanga

authors: Roa, Tom

subjects: Tikanga Māori

abstract: This paper is a preliminary report on an ongoing research project begun in 1999. The project involves consultation with Waikato-Tainui, the tāngata whenua of the Waikato region, about the construction of guidelines for University of Waikato staff (both Māori and non-Māori) who are involved in gatherings that call for adherence to Tainui protocols. Here, the emphasis is on guidelines for the conduct of pōwhiri (formal welcomes) on the University Marae.

text: Tikanga Tainui: Tikanga whare wānanga This paper is a preliminary report on an ongoing research project begun in 1999. The project involves consultation with Waikato-Tainui, the tāngata whenua of the Waikato region, about the construction of guidelines for University of Waikato staff (both Māori and non-Māori) who are involved in gatherings that call for adherence to Tainui protocols. Here, the emphasis is on guidelines for the conduct of pōwhiri (formal welcomes) on the University Marae.

year: 2005-09