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32 results on '"Pitz, Greg A."'

3. Analyzing the potential of ion chambers to measure laser-induced ionization rates.

Author

Oliker, Benjamin, Pitz, Greg, Hostutler, David A., Madden, Timothy, and Rudolph, Wolfgang

Subjects
*IONIZATION chambers, *LASER plasmas, *ELECTRON temperature, *BEHAVIORAL assessment, *PLASMA density
Abstract

We demonstrate and analyze the use of an ion chamber for measuring laser-induced ionization in cesium gas for the first time, which is of recent interest due to research in diode pumped alkali lasers (DPALs). In this report, the viability of an ion chamber diagnostic with high plasma density and ionization localized to a laser beam is investigated. A simulation of the laser-induced plasma in the ion chamber, based on the Thomson model with diffusion, is developed and will be shown to display similar qualitative behavior to measurements, and bound test results within model uncertainty. The analysis will show that complex processes occur: (1) space-charge limited ion drift, (2) Debye shielding preventing the electric field from penetrating a bulk plasma region, and (3) ambipolar diffusion across the bulk with possibly elevated electron temperature. However, these processes are well understood and do not limit the accuracy of an ion chamber diagnostic for laser-induced ionization rate measurement. [ABSTRACT FROM AUTHOR]

Published
2025
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14. Collisional Dynamics of the Cesium D1 and D2 Transitions

Author

AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING, Pitz, Greg A., AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING, and Pitz, Greg A.

Abstract

The collisional dynamics of the 6(2)P levels in cesium have been studied utilizing steady state laser absorption and laser induced florescence techniques. In addition the production of a blue beam produced by two photon absorption has been observed in potassium., The original document contains color images.

Published
2010

25. Effect of Residence Time on Singlet Oxygen Production in Microwave and RF Discharges.

Author

Lange, Matthew A., Pitz, Greg A., and Perram, Glen P.

Subjects
*REACTIVE oxygen species, *RADIO frequency discharges, *MICROWAVES, *IODINE lasers, *ELECTRON distribution, *LASER beams, *NONLINEAR optics
Abstract

The evolution of singlet oxygen inside both microwave and RF discharges of pure oxygen has been observed for residence times of 0.1-2 ms, achieving a steady value within 1 ms. The corresponding limiting yields decrease inversely with oxygen pressure in the range 2-8 Torr. A kinetic analysis is presented suggesting a second order process for the deactivation of O2(a) that scales with electron number density. The pseudo first order decay rates in a microwave discharge are high, ∼6,000 s-1, and slower in an RF discharge, 300-500 s-1. In both cases the decay rate is independent of oxygen pressure and flow rate. The role of vibrationally excited ground state oxygen is largely unexplored and may offers one possible mechanism. The results are consistent with a three-body atomic oxygen reaction only if the electron number density increases with oxygen pressure, in contradiction to the reported modeling results. [ABSTRACT FROM AUTHOR]

Published
2010
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29. Transfer between the cesium 6²P1/2 and 6²P3/2 levels induced by collisions with H2, HD, D2, CH4, C2H6, CF4, and C2F6.

Author

Pitz, Greg A., Fox, Charles D., and Perram, Glen P.

Subjects
*SPIN-orbit interactions, *CESIUM, *FLUORESCENCE, *PROBABILITY theory, *COLLISIONS (Nuclear physics)
Abstract

The cross sections of spin-orbit energy exchange between the cesium 6²P1/2 ↔ 6²P3/2 states induced by collisions with N2, H2, HD, D2, CH4, C2H6, CF4, and C2F6 were obtained for pressures less than 100 Torr at room temperature by means of steady-state laser-induced fluorescence techniques. The spin-orbit energy exchange rate with N2, H2, HD, D2, CH4, C2H6, CF4, and C2F6, have been measured as σ21(6²P3/2 ↔ 6²P1/2) = 16.3, 34.1, 30.0, 22.7, 21.4, 65.6, 64.8, and 137 Ų and σ12(6²P1/2 → 6²P3/2) = 1.8, 4.4, 4.1, 3.0, 2.9, 13.3, 9.7, and 16.3 Ų, respectively. Correlations of the spin-orbit transfer probabilities with rotational-energy defect and vibrational-energy defect have been shown. [ABSTRACT FROM AUTHOR]

Published
2011
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