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The thesis concerns experimental studies of discharge excited lasers operating in the vacuum ultraviolet (VUV) region of the spectrum. The known molecular fluorine laser operating at 157nm, on a bound- to-bound transition of the F₂ molecule was selected for initial study. As a result of the work reported here the energy per pulse was increased by a factor of five (10mJ to 50mJ) from that of earlier F₂ lasers. Similary the working lifetime of the gas mixture was increased from a few shots to several thousand by the application of cryogenic gas purification techniques. These improvements have resulted in the development of a practical commercial F₂ laser. The performance characteristics of the fluorine laser and their relationship to the physical mechanisms are discussed. With the objective of achieving laser action in the 110 to 130nm region of the VUV a novel scheme is investigated. The scheme involves the production of a population inversion between the v'=1 level of the b¹π_u state of molecular nitrogen and high lying levels of the X¹Σ_g ground state. The excitation of the upper laser level involves production of N₂ molecules in the a¹π_g state by means of a pulsed discharge. Transfer of population from this intermediate 'a' state to the upper level is accomplished by absorption of radiation at 308nm from a discharge excited xenon chloride laser. The practicality of this scheme has been investigated to the extent that populations of the order of 10¹³ molecules per cm³ have been produced in the 'a' state and laser induced fluorescence on the 'b' to 'X' band has been observed. Under the conditions of "the present experiments the potential VUV gain is too small (10^-4cm<sup>-1>/sup>) to reach laser threshold. The problems of increasing the gain to reach threshold for a practical device are discussed.

A histological investigation of the effects of ultraviolet (UV) radiation upon the skin of four species of teleost fish was conducted in an attempt to define the sequential pathogenesis of the UV induced lesion. The species used in the experiments, namely plaice Pleuronectes platessa L., turbot Scophthalmus znax.zmus (L.), rainbow trout, Sairno gairdneri Richardson and Atlantic salmon, Salrno salar L. represent species reared commercially and thus likely, in the artificial environment of a fish farm, to receive levels of solar radiation in excess of those encountered in nature. It was found that plaice were the most susceptible species to UV radiation whilst turbot were marginally less so. Rainbow trout and Atlantic salmon showed similar levels of susceptibility when compared with each other but, in addition, had significantly higher tolerance thresholds than either plaice or turbot. Whilst the use of artificial radiation sources allows for more accurate control over irradiance than would natural sunlight, the need to recognise the limitations of such sources has been emphasised. In addition the importance of incorporating filters to remove the shorter wavelengths which would not be encountered at the earth's surface has been demonstrated. The photoreactive capability/capability of fish skin to repair cell damage initiated by UV radiation has been shown by the use of variable light input in the visible spectrum. The use of scanning electron microscopy to examine the surface topography of the radiation lesion confirmed the observations made by light microscopy and demonstrated the vulnerability of the damaged skin surface to the invasion of opportunistic bacteria. The importance of recognising sunlight as an environmental factor in the initiation of dorsal skin damage is no longer in doubt; experimental evidence and clinical observations on high altitude fish farms confirm this. Consideration is also given to the implications of prolonged exposure to sunlight upon fish following transfer and handling. The possible role of sunlight in the aetiology of certain bacterial skin diseases in farmed and wild fish and in dorsal skin neoplasms in wild fish is discussed.

[Abstract]This dissertation presents the development, testing and application of a chemical film UV dosimeter based on the polymer Poly (2, 6-dimethyl-1, 4-phenylene oxide) (PPO) prepared especially for long – term high – exposure underwater use. Initial testing of the dosimeter was performed in a water tank within a controlled laboratory environment with an artificial UV source in which various optical and physical properties of the film were rigorously tested such as UV dose and depth response, cosine response, interdosimeter variation, dose rate independence, dark reaction, watermarking effect, exposure additivity and visible and UVA wavelength response. In each of these tests the PPO dosimeter displayed results proving that it could be reliably used in aquatic environments at a level of accuracy only slightly lower than what could be expected for in – air dosimetric measurements. The use of a polyethylene derived neutral density filter (NDF) was then employed with the PPO dosimeter in order to extend exposure time. Results from this investigation showed that the polyethylene NDF could extend the effective life time of the PPO dosimeter by as much as five days in early autumn. Following this the PPO dosimeter was calibrated in the field to the solar erythemal action spectrum in – air and to the solar UVB spectrum in clear water, creek water, sea water and dam water over the duration of a year. In both the in – air and underwater calibrations it was found that the response of the PPO dosimeter lasted over a much greater amount of time when compared to the more commonly used polysulphone dosimeter and also varied with the modulation of the incident solar spectrum brought on by changing SZA and fluctuations in atmospheric column ozone. Additionally, it was discovered that in – air and underwater calibration regimes could not be interchanged and that the PPO dosimeter response underwater is dependent upon water type, but only when transmission spectra differed between two water types by a difference on average of more than 5% across the UVB waveband. As a final test, the PPO dosimeter was deployed over a year to take UVB exposure measurements with the use of a custom built submersible float in three different real – world field environments that included a creek, a sea water tank and a stagnant dam. Exposures could be measured reliably up to a depth of 5 cm in the creek water and the dam water and up to and possibly beyond a depth of 35 cm in the sea water. From the sea water PPO dosimeter measurements a series of attenuation coefficients were estimated for each season. These coefficients showed reasonable agreement when compared to attenuation coefficient calculations made using a calibrated spectrometer in the same sea water, further proving the usefulness of the PPO dosimeter.

Thesis (Ph. D.)--University of Adelaide, Dept. of Physics, 1983. / Includes bibliographical references (leaves [250]-268).

Diss. (sammanfattning) Göteborg : Göteborgs universitet, 2006. / Härtill 4 uppsatser.

Thesis (M.S. in Physics)--Naval Postgraduate School, December 1990. / Thesis Advisor(s): Cleary, David D. ; Davis, D. Scott. "December 1990." Description based on title screen as viewed on April 2, 2010. DTIC Identifier(s): Ionosphere, Ultraviolet Spectroscopy, Interferometer. Author(s) subject terms: Ionosphere, Ultraviolet Spectroscopy, Interferometer. Includes bibliographical references (p. 64-67). Also available in print.

Thesis (Ph. D.)--Lehigh University, 2004. / Includes bibliographical references and vita.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: C. Grant Willson. Vita. Includes bibliographical references.