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Articles 1 - 13 of 13
Full-Text Articles in Physics
Analysis Of Adsorbed Contaminants Of Caf2 Surfaces By Infrared Laser Induced Desorption, Jinmei Fu, Yamini Surapaneni, Susan D. Allen
Analysis Of Adsorbed Contaminants Of Caf2 Surfaces By Infrared Laser Induced Desorption, Jinmei Fu, Yamini Surapaneni, Susan D. Allen
Susan D. Allen
157 nm photolithography technologies are currently under development and have been accepted as the leading candidate for fabrication of the next generation semiconductor devices after 193 nm. At this and shorter wavelengths, molecular contamination of surfaces becomes a serious problem as almost all molecules absorb at 157 nm and below. The light transmitted by a photolithographic tool can be significantly decreased by the presence of a few monolayers adsorbed on its many optical surfaces. We have developed a laser induced desorption, electron impact ionization, time-of-flight mass spectrometer (LID TOFMS) to study contaminants on 157nm and other ultraviolet optics, e.g., polished …
Investigation Of (E, 2e) Collisions And Related Phenomena, Jason Manuel Martinez
Investigation Of (E, 2e) Collisions And Related Phenomena, Jason Manuel Martinez
Physics Theses & Dissertations
In this thesis I investigate (e, 2e) processes, or electron impact ionization, using several theoretical methods. I first examine the problem using the Born approximations, particularly the Distorted Wave Born Approximation (DWBA), focusing on the underlying processes that dominate for ionization of the 2p state of Argon and Magnesium. I investigate as well the ionization of helium and hydrogen and use the simplicity of the approximation to probe the incident particle effects on the Helium cross section. In both cases the results are compared with experiment. I also produce cross section results for ions near threshold, a regime that …
Doubly Differential Single And Multiple Ionization Of Krypton By Electron Impact, O. G. De Lucio, Jared M. Gavin, Robert D. Dubois
Doubly Differential Single And Multiple Ionization Of Krypton By Electron Impact, O. G. De Lucio, Jared M. Gavin, Robert D. Dubois
Physics Faculty Research & Creative Works
Differential measurements for single and multiple ionization of Kr by 240 and 500 eV electron impact are presented. Using a pulsed extraction field, Kr+, Kr2+, and Kr3+ ions were measured in coincidence with scattered electrons for energy losses up to 120 eV and scattering angles between 16° and 90°. Scaling properties of the doubly differential cross sections (DDCS) are investigated as a function of energy loss, scattering angle, and momentum transfer. It is shown that scaling the DDCS as outlined by Kim and Inokuti and plotting them versus a parameter consisting of the momentum transfer divided by the square root …
Unexpected Higher-Order Effects In Charged Particle Impact Ionization At High Energies, M. Foster, Jerry Peacher, Michael Schulz, Don H. Madison, Zhangjin Chen, H. R. J. Walters
Unexpected Higher-Order Effects In Charged Particle Impact Ionization At High Energies, M. Foster, Jerry Peacher, Michael Schulz, Don H. Madison, Zhangjin Chen, H. R. J. Walters
Physics Faculty Research & Creative Works
Most of the experimental and theoretical studies of electron-impact ionization of atoms, referred to as (e, 2e), have concentrated on the scattering plane. The assumption has been that all the important physical effects will be observable in the scattering plane. However, very recently it has been shown that, for C6+-helium ionization, experiment and theory are in nice agreement in the scattering plane and in very bad agreement out of the scattering plane. This lack of agreement between experiment and theory has been explained in terms of higher-order scattering effects between the projectile and target ion. We have examined electron-impact ionization …
Kinematically Complete Experiment On Single Ionization In 75-Kev P+He Collisions, Michael Schulz, Ahmad Hasan, N. V. Maydanyuk, M. Foster, B. Tooke, Don H. Madison
Kinematically Complete Experiment On Single Ionization In 75-Kev P+He Collisions, Michael Schulz, Ahmad Hasan, N. V. Maydanyuk, M. Foster, B. Tooke, Don H. Madison
Physics Faculty Research & Creative Works
We have measured and calculated fully differential single-ionization cross sections for the complete three-dimensional space in 75 keV p+He collisions. Several signatures of the projectile-residual-target-ion interaction, some of which are not observable for fast projectiles and for electron impact, are revealed. Some of these features are qualitatively reproduced by our calculations if this interaction is accounted for. However, overall the agreement between theory and experiment is not very good. Thus, our understanding of effects caused by the projectile-residual-target-ion interaction appears to be rather incomplete.
Interference Effects For Low-Energy Electron-Impact Ionization Of Nitrogen Molecules, Junfang Gao, Don H. Madison, Jerry Peacher
Interference Effects For Low-Energy Electron-Impact Ionization Of Nitrogen Molecules, Junfang Gao, Don H. Madison, Jerry Peacher
Physics Faculty Research & Creative Works
Young's double slit interference effects for low incident energy 75.6 eV electron impact ionization of N2 are investigated using the distorted-wave impulse approximation (DWIA) for both coplanar symmetric and asymmetric scattering. Although the DWIA does not predict observable interference effects for the coplanar symmetric case, it predicts some strong Young's double-slit-type interference effects for the highly asymmetric scattering case. These effects are strong enough that they should be experimentally observable if one can make measurements in the backscattering region.
Fully Differential Cross Sections For Low-Energy Electron-Impact Ionization Of Nitrogen Molecules, Junfang Gao, Don H. Madison, Jerry Peacher
Fully Differential Cross Sections For Low-Energy Electron-Impact Ionization Of Nitrogen Molecules, Junfang Gao, Don H. Madison, Jerry Peacher
Physics Faculty Research & Creative Works
Currently there is no accurate theoretical approach available for treating fully differential cross sections (FDCS) for low-energy electron-impact ionization of large molecules. For high incident energies, the plane wave impulse approximation (PWIA) generally yields good agreement with experimental data. In this paper, the distorted wave impulse approximation (DWIA) is used to calculate FDCS for low-energy electron-impact ionization of N2. To perform the necessary average over all molecular orientations, we propose an orientation average (OA) approximation. Although the DWIA results represent an improvement over the PWIA for intermediate energies, an improved theory is necessary for lower energies. However, the OA approximation …
Analysis Of Adsorbed Contaminants Of Caf/Sub 2/ Surfaces By Infrared Laser Induced Desorption, Jinmei Fu, Yamini Surapaneni, Susan D. Allen
Analysis Of Adsorbed Contaminants Of Caf/Sub 2/ Surfaces By Infrared Laser Induced Desorption, Jinmei Fu, Yamini Surapaneni, Susan D. Allen
Mechanical Engineering - Daytona Beach
157 nm photolithography technologies are currently under development and have been accepted as the leading candidate for fabrication of the next generation semiconductor devices after 193 nm. At this and shorter wavelengths, molecular contamination of surfaces becomes a serious problem as almost all molecules absorb at 157 nm and below. The light transmitted by a photolithographic tool can be significantly decreased by the presence of a few monolayers adsorbed on its many optical surfaces. We have developed a laser induced desorption, electron impact ionization, time-of-flight mass spectrometer (LID TOFMS) to study contaminants on 157nm and other ultraviolet optics, e.g., polished …
Doubly Differential Multiple Ionization Of Krypton By Positron And Electron Impact, Kay Dubois, Antonio C. Santos, Ahmad Hasan
Doubly Differential Multiple Ionization Of Krypton By Positron And Electron Impact, Kay Dubois, Antonio C. Santos, Ahmad Hasan
Physics Faculty Research & Creative Works
Measurements of doubly differential single and multiple ionization of krypton atoms have been performed for 750 eV positron and electron impact. Data were measured as a function of projectile energy-loss and scattering angle. For electrons, the energy-loss range was 0-85% of the initial projectile energy and scattering angles were between ±22°. Following the procedure adopted previously for argon, the electron impact data were placed on an absolute scale by normalizing to total ionization cross sections available in the literature. The present results for krypton show differences between positron and electron impact that are less pronounced than was found for argon. …
Are Microbubbles Necessary For The Breakdown Of Liquid Water Subjected To A Submicrosecond Pulse?, R. P. Joshi, J. Qian, G. Zhao, J. Kolb, K. H. Schoenbach, E. Schamiloglu, J. Gaudet
Are Microbubbles Necessary For The Breakdown Of Liquid Water Subjected To A Submicrosecond Pulse?, R. P. Joshi, J. Qian, G. Zhao, J. Kolb, K. H. Schoenbach, E. Schamiloglu, J. Gaudet
Electrical & Computer Engineering Faculty Publications
Electrical breakdown in homogeneous liquid water for an ∼ 100 ns voltage pulse is analyzed. It is shown that electron-impact ionization is not likely to be important and could only be operative for low-density situations or possibly under optical excitation. Simulation results also indicate that field ionization of liquid water can lead to a liquid breakdown provided the ionization energies were very low in the order of 2.3eV. Under such conditions, an electric-field collapse at the anode and plasma propagation toward the cathode, with minimal physical charge transport, is predicted. However, the low, unphysical ionization energies necessary for matching …
Probing Scattering Wave Functions Close To The Nucleus, Don H. Madison, Daniel Fischer, Matthew S. Foster, Michael Schulz, Robert Moshammer, Stephenie J. Jones, Joachim Hermann Ullrich
Probing Scattering Wave Functions Close To The Nucleus, Don H. Madison, Daniel Fischer, Matthew S. Foster, Michael Schulz, Robert Moshammer, Stephenie J. Jones, Joachim Hermann Ullrich
Physics Faculty Research & Creative Works
Recently, three-dimensional imaging of the ejected electrons following 100 MeV/amu C6+ single ionization of helium led to the observation of a new structure not predicted by theory [M. Schulz et al., Nature (London) 422, 48 (2003)]. Instead of the usual “recoil lobe” centered on the momentum-transfer axis, a ring-shaped structure centered on the beam axis was observed. New measurements at 2 MeV/amu exhibit a similar structure, which is now predicted by theory. We argue that the same theory failed at 100 MeV/amu because the faster projectiles probe distances much closer to the nucleus, where our multiple-scattering model is expected …
Ionization-Excitation Of Helium By Fast Charged Particles, L. Nagy, J. Wang, Jack C. Straton, James H. Mcguire
Ionization-Excitation Of Helium By Fast Charged Particles, L. Nagy, J. Wang, Jack C. Straton, James H. Mcguire
Physics Faculty Publications and Presentations
Probabilities and cross sections for ionization plus excitation in helium produced by fast heavy-particle impact have been evaluated. In these calculations, contributions from shake-off, time ordering, and independent interactions of the frozen-target electrons with the projectile are included. A comparison is made to recent experimental observations for the ratio of excitation-ionization to single-ionization total cross sections. A comparison is also made to calculations of excitation-ionization by fast electron impact.
Cation Production And Reactions Induced By Electron Impact On Tetraethoxysilane, Jeremy C. Holtgrave
Cation Production And Reactions Induced By Electron Impact On Tetraethoxysilane, Jeremy C. Holtgrave
Theses and Dissertations
The production of cations by electron impact on tetraethoxysilane (TEOS) is studied with a Fourier Transform mass spectrometer (FTMS). The operating principles of FTMS are reviewed and the experimental approach to the mass calibration and cross-section measurement is discussed. The cross-sections for total and partial ionization of Si(OC2H5)4 from threshold to 50 eV are measured. Also, the ion chemistry resulting from interactions between ions and neutral TEOS is examined.