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Full-Text Articles in Physical Sciences and Mathematics
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 …
Tev Black Hole Fragmentation And Detectability In Extensive Air Showers, Eun-Joo Ahn, Maximo Ave, Marco Cavaglia, Angela V. Olinto
Tev Black Hole Fragmentation And Detectability In Extensive Air Showers, Eun-Joo Ahn, Maximo Ave, Marco Cavaglia, Angela V. Olinto
Physics Faculty Research & Creative Works
In models with large extra dimensions, particle collisions with a center-of-mass energy larger than the fundamental gravitational scale can generate nonperturbative gravitational objects. Since cosmic rays have been observed with energies above 108 TeV, gravitational effects in the TeV energy range can, in principle, be observed by ultrahigh energy cosmic ray detectors. We consider the interaction of ultrahigh energy neutrinos in the atmosphere and compare extensive air showers from TeV black hole formation and fragmentation with standard model processes. Departures from the standard model predictions arise in the interaction cross sections and in the multiplicity of secondary particles. Large …
Quantum Mechanical Calculations Of Monoxides Of Silicon Carbide Molecules, John W. Roberts Jr.
Quantum Mechanical Calculations Of Monoxides Of Silicon Carbide Molecules, John W. Roberts Jr.
Theses and Dissertations
Modern semiconductor devices are principally made using the element silicon. In recent years, silicon carbide (SiC), with its wide band-gap, high thermal conductivity, and radiation resistance, has shown prospects as a semiconductor material for use in high temperature and radiation environments such as jet engines and satellites. A limiting factor in the performance of many SiC semiconductor components is the presence of lattice defects formed at oxide dielectric junctions during processing. Recent theoretical work has used small quantum mechanical systems embedded in larger molecular mechanics structures to attempt to better understand SiC surfaces and bulk materials and their oxidation. This …
Building Blocks For Time-Resolved Laser Emission In Mid-Infrared Quantum Well Lasers, Gabriel D. Mounce
Building Blocks For Time-Resolved Laser Emission In Mid-Infrared Quantum Well Lasers, Gabriel D. Mounce
Theses and Dissertations
The objective of this research is to improve the performance of mid-infrared semiconductor quantum-well lasers. Lasers operating in the mid-infrared are useful for many Air Force applications which include infrared (IR) countermeasures in particular. Countermeasure applications require lasers that are compact, and able to emit at high powers while operating at room temperature. Limits to power increases are seen in the transverse modal development of laser oscillation. These modes typically form in the waveguiding active region contributing to the laser output. However, competing modes outside of this region also develop when the confining structural layers have the right characteristics. These …
Disorder-Induced Rounding Of Certain Quantum Phase Transitions, Thomas Vojta
Disorder-Induced Rounding Of Certain Quantum Phase Transitions, Thomas Vojta
Physics Faculty Research & Creative Works
We study the influence of quenched disorder on quantum phase transitions in systems with overdamped dynamics. For Ising order-parameter symmetry disorder destroys the sharp phase transition by rounding because a static order parameter can develop on rare spatial regions. This leads to an exponential dependence of the order parameter on the coupling constant. At finite temperatures the static order on the rare regions is destroyed. This restores the phase transition and leads to a double exponential relation between critical temperature and coupling strength. We discuss the behavior based on Lifshitz-tail arguments and illustrate the results by simulations of a model …
Perturbative And Nonperturbative Calculations Of Electron-Hydrogen Ionization, Stephenie J. Jones, Don H. Madison, Mark D. Baertschy
Perturbative And Nonperturbative Calculations Of Electron-Hydrogen Ionization, Stephenie J. Jones, Don H. Madison, Mark D. Baertschy
Physics Faculty Research & Creative Works
We compare calculations of the fully differential cross section for ionization of atomic hydrogen by electron impact using two different theories-the perturbative CDW-EIS (continuum distorted wave with eikonal initial state) approximation and the nonperturbative ECS (exterior complex scaling) method. For this comparison, we chose an impact energy of 54.4 eV, since this is near the lowest energy that our perturbative approach would be applicable and near the highest energy that can be tackled by the ECS method with our present computational resources. For the case of equal-energy outgoing electrons investigated here, the two theories predict nearly identical results except that …