No description available.

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 346-352).

Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 106-109).

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 191-203).

Sensitive and selective absorption spectroscopy techniques are applied to the detection of the excited species present in a range of low pressure inductively coupled plasmas (ICPs). The state densities and temperatures of various species are investigated across the parameter space accessible (plasma power and pressure) to aid in the understanding of the kinetic processes occurring. The experimental methods are based upon various forms of absorption spectroscopy, incorporating wavelength modulation and/or an optical enhancement cavity. The probing radiation is generated either directly using a CW diode laser or indirectly through the use of frequency conversion techniques. The absolute number densities of all four levels (1s₂, 1s₃, 1s₄ and 1s₅) present in the first excited manifold of atomic argon and neon are determined as a function of plasma operating conditions. A kinetic model is constructed to simulate these populations using cross-sections taken from the literature together with further measurements on the electron density and temperature obtained with a Langmuir probe. The model elucidates the importance of populational redistribution within the 1s manifold via excitation to the 2p_n levels, and highlights the mechanism of radiative decay (with radiative trapping taken into account) as the ultimate loss route for the 1s manifold. Measurements are made using cavity enhanced absorption spectroscopy (CEAS) on the 2p₅ and 2p₆ state densities in argon in order to draw additional conclusions about the nature of the discharge and to verify the kinetic model. The populations of the 1s₃ and 1s₄ states are probed in a neon plasma with helium, argon and nitrogen as a dopant gas, with the aim of manipulating the EEDFs. The addition of N₂ and Ar to the neon discharge resulted in a reduction in the 1s₃ and 1s₄ populations, while the addition of He resulted in an increase. These observations are consistent with a decrease and an increase, respectively, in the electron temperatures. The populations of the vibrational levels v = 0, 1, 3, and 6 of the A(³Σ_u⁺) state of molecular nitrogen are determined as a function of plasma operating conditions in a N₂ discharge using CEAS. A selection of vibrational bands within the B(³Π_g)←A(³Σ_u⁺) system are probed, with calibration achieved using cavity ring-down spectroscopy. At 25 mTorr and 200 W power the populations of the v = 0, 1,3, and 6 levels are (1.31 ± 0.16) × 10¹¹ cm^-3, (8.44 ± 1.01) × 10¹⁰ cm^-3, (2.83 ± 0.34) × 10¹⁰ cm^-3 and (5.27 ± 0.63) × 10⁹ cm^-3, respectively, corresponding to a vibrational temperature of 3600 ± 150 K. In addition, the observation of the N₂⁺(X²Σ_g⁺) molecular ion in v = 0 using both CEAS and CEAS in combination with wavelength modulation spectroscopy is presented (which is found to improve the sensitivity for this measurement by approximately an order of magnitude). At 10 mTorr and 400 W the total population in N₂⁺(X²Σg⁺, v = 0) is (1.26 ± 0.15) × 10⁹ molecules cm^-3, consistent with data obtained using a Langmuir probe. The density of oxygen atoms present in their ground state (³P₂) is investigated using the technique of CEAS, and at 500 W and 100 mTorr the concentration is estimated to be (2.2 ± 0.3) × 10¹⁴ cm^-3. This corresponds to a dissociation efficiency, δ, of O₂ of 0.06. Furthermore, a difference frequency generation (DFG) system is constructed to generate radiation at 1.9 μm in order to probe the (0,0) band of the O₂(b¹Σ_g⁺←a¹Δ_g) quadrupolar system. A minimum detectable absorbance of 1.3 × 10^-5 over a 10 cm cell is determined by calibrating the system on an ammonia absorption, placing a limit of 1.8 × 10¹⁶ cm^-3 on the total v = 0 population of O₂(a¹Δ_g) in a microwave discharge operating with 5 Torr pure O₂.

No description available.

No description available.

Chemical Oxygen Iodine Laser(COIL) is an electronic transition high energy chemical laser having a wavelength of 1.315 /mi. This is the first chemical laser to operate on an electronic rather than a rotational or vibrational transition. In principle the COIL can be operated either in pulsed or cw mode. Its interest lies in high chemical efficiency, high power and wavelength which is shortest among all the chemical lasers. COIL finds a wide range of applications as its output wavelength at 1.315/zm couples well with the surface of most metals. The applications include surface hardening and modification of metals, welding, drilling and cutting of metals, cutting of ceramics, micro machining, laser deposition of non metallic coatings on metallic surfaces, monitoring of atmospheric pollutants and solar hazardous waste detoxification. Moreover, its wavelength is suitable for fiber optic transmission. In COIL the laser output at 1.315 /an is achieved by stimulated emission on the f (2-PL/2) -* -f (2-p3/2) magnetic dipole transition in atomic iodine. The population inversion on this transition is obtained by resonant collisions! energy transfer from metastable excited Oj^A) molecules produced by a chemical reaction of KOH, H2O? and Cl2. The chemical reaction of H2O2 and Cl2 that produces oxygen molecules is highly exothermic, and because of spin conservation considerations, channels its energy directly into the metastable electronically excited singlet delta state of oxygen molecule. Since the O2(1A) has a 45 mins lifetime and hence an extremely low small signal gain coefficient, it cannot be lased directly. Lasing can be achieved, however, if this energy is transferred to an atom or molecule which has a reasonable transition moment between its excited and ground states. The iodine 52P^2 -> 52P3/2 magnetic dipole transition has an acceptable transition moment and is nearly resonant with the 02{lA) state in oxygen. Excited iodine atoms are obtained by mixing O2(l A) and l2 molecules resulting in their dissociation and subsequent excitation. Power levels in excess of 25 kW have been reported in COIL. Due to wide range of applications and mainly for its use as a laser weapon, efforts are being made to enhance the power to higher levels. The dissociation of I2 controls the gain of the coil and hence power. In the pure COIL scheme some of the I2 remains undissociated due to the recombination reactions. Hence if we add a mechanism to dissociate the residual I2 molecules, we can enhance the performance of the COIL. So we propose to add a solar pumping to conventional COIL, which by photo exciting the undissociated I2lead to increase in efficiency. The thesis contains six chapters in which chapter 1 contains a general introduction and the definition of the research problem. The basic theory and the chemical reactions are discussed in chapter 2, The proposed model is discussed and the rate equations are solved in chapter 3. The numerical scheme and the computer code along-with the validation of the code are presented in chapter 4. The numerical results for the species concentrations, population inversion density and the output power for the proposed solar pumped COIL are presented in chapter 5, Final conclusions and future scope of the proposed research are presented in the final chapter 6. (Pl refer the original document for formulas)