Physical Sciences and Mathematics Commons^™

Rescattering Of Ultralow-Energy Electrons For Single Ionization Of Ne In The Tunneling Regime, Robert Moshammer, Joachim Hermann Ullrich, Bernold Feuerstein, Daniel Fischer, Alexander Dorn, Claus Dieter Schroter, Jose R. Crespo Lopez-Urrutia, C. Hoehr, Horst Rottke, Christoph Trump, M. Wittmann, Georg Korn, Wolfgang Sandner

Physics Faculty Research & Creative Works

Electron emission for single ionization of Ne by 25 fs, 1.0 PW/cm² laser pulses at 800 nm was investigated. Kinematics was studied using a 'reaction microscope'. Results showed a zero longitudinal momentum of a low-energy electron with high resolution.

Two-Loop Bethe-Logarithm Correction In Hydrogenlike Atoms, Krzysztof Pachucki, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

We calculate the two-loop Bethe logarithm correction to atomic energy levels in hydrogenlike systems. The two-loop Bethe logarithm is a low-energy quantum electrodynamic (QED) effect involving multiple summations over virtual excited atomic states. Although much smaller in absolute magnitude than the well-known one-loop Bethe logarithm, the two-loop analog is quite significant when compared to the current experimental accuracy of the 1 S – 2 S transition: It contributes - 8.19 and - 0.84 k H z for the 1 S and the 2 S state, respectively. The two-loop Bethe logarithm has been the largest unknown correction to the hydrogen Lamb …

Afci Quarterly Input – Unlv July Through September, 2003, Harry Reid Center For Environmental Studies. Nuclear Science And Technology Division

Transmutation Research Program Reports (TRP)

Quarterly report highlighting research projects and objectives of the Transmutation Research Program at the Nuclear Science & Technology Division, Harry Reid Research Center.

The University of Nevada, Las Vegas supports the AFCI through research and development of technologies for economic and environmentally sound refinement of spent nuclear fuel. The UNLV program has four components: infrastructure, international collaboration, student-based research, and management and program support.

Geometry And Topology Of Escape. Ii. Homotopic Lobe Dynamics, K. A. Mitchell, J. P. Handley, John B. Delos, Stephen Knudson

Arts & Sciences Articles

We continue our study of the fractal structure of escape-time plots for chaotic maps. In the preceding paper, we showed that the escape-time plot contains regular sequences of successive escape segments, called epistrophes, which converge geometrically upon each end point of every escape segment. In the present paper, we use topological techniques to: (1) show that there exists a minimal required set of escape segments within the escape-time plot; (2) develop an algorithm which computes this minimal set; (3) show that the minimal set eventually displays a recursive structure governed by an “Epistrophe Start Rule:” a new epistrophe is spawned …

Black Hole Multiplicity At Particle Colliders (Do Black Holes Radiate Mainly On The Brane?), Marco Cavaglia

Physics Faculty Research & Creative Works

If gravity becomes strong at the TeV scale, we may have the chance to produce black holes at particle colliders. In this Letter we revisit some phenomenological signatures of black hole production in TeV-gravity theories. We show that the bulk-to-brane ratio of black hole energy loss during the Hawking evaporation phase depends crucially on the black hole greybody factors and on the particle degrees of freedom. Since the greybody factors have not yet been calculated in the literature, and the particle content at trans-Planckian energies is not known, it is premature to claim that the black hole emits mainly on …

Substrate Specificity, Metal Binding Properties, And Spectroscopic Characterization Of The Dape-Encoded N-Succinyl-L,L-Diaminopimelic Acid Desuccinylase From Haemophilus Influenzae, David L. Bienvenue, Danuta M. Gilner, Ryan S. Davis, Brian Bennett, Richard C. Holz

Physics Faculty Research and Publications

The catalytic and structural properties of divalent metal ion cofactor binding sites in the dapE-encoded N-succinyl-l,l-diaminopimelic acid desuccinylase (DapE) from Haemophilus influenzae were investigated. Co(II)-substituted DapE enzyme was 25% more active than the Zn(II)-loaded form of the enzyme. Interestingly, Mn(II) can activate DapE, but only to ∼20% of the Zn(II)-loaded enzyme. The order of the observed k_cat values are Co(II) > Zn(II) > Cd(II) > Mn(II) >Ni(II) ∼ Cu(II) ∼ Mg(II). DapE was shown to only hydrolyze l,l-N-succinyl-diaminopimelic acid (l,l-SDAP) and was inactive toward d,l-, l,d-, and d,d-SDAP. DapE was also inactive toward several acetylated amino acids as …

Quantum Melting Of The Charge-Density-Wave State In 1t-Tise2, C. S. Snow, J. F. Karpus, S. L. Cooper, T. E. Kidd, T.-C. Chiang

Faculty Publications

We report a Raman scattering study of low-temperature, pressure-induced melting of the charge-density- wave (CDW) phase of 1T-TiSe₂. Our measurements reveal that the collapse of the CDW state occurs in three stages: (i) For P<5 kbar, the pressure dependence of the CDW amplitude mode energies and intensities are indicative of a ‘‘crystalline’’ CDW regime; (ii) for 5<P<25 kbar, there is a decrease in the CDW amplitude mode energies and intensities with increasing pressure that suggests a regime in which the CDW softens, and exhibits enhanced fluctuations; and (iii) for P > 25 kbar, the absence of amplitude modes reveals a metallic regime in which the CDW has melted.

Geometry And Topology Of Escape. I. Epistrophes, K. A. Mitchell, J. P. Handley, B. Tighe, John B. Delos, Stephen Knudson

Arts & Sciences Articles

We consider a dynamical system given by an area-preserving map on a two-dimensional phase plane and consider a one-dimensional line of initial conditions within this plane. We record the number of iterates it takes a trajectory to escape from a bounded region of the plane as a function along the line of initial conditions, forming an “escape-time plot.” For a chaotic system, this plot is in general not a smooth function, but rather has many singularities at which the escape time is infinite; these singularities form a complicated fractal set. In this article we prove the existence of regular repeated …

Measurement Of The Nonlinear Refractive Index (N2) And Stimulated Raman Scattering In Optical Fibers As A Function Of Germania Content, Using The Photorefractive Beam Coupling Technique, Ferdinand Anayo Oguama

Dissertations

One of the greatest challenges in optical communication is the understanding and control of optical fiber nonlinearities. While these nonlinearites limit the power handling capacity of optical fibers and can cause noise, signal distortion and cross talk in optically amplified transmission systems, they have been equally harnessed for the development of new generations of optical amplifiers and tunable laser sources. The two prominent parameters that characterize the nonlinear properties of an optical fiber are the nonlinear refractive index n₂ and the Raman gain coefficient g_R. These parameters are related to the third order nonlinear susceptibility [x^{(3) …}

Understanding The Origins Of Metastability In Thin Film Growth; Tantalum And The Early Group Vb-Vib Metals, Neme Okechukwu Nnolim

Dissertations

Tantalum (Ta) is a metal that is highly prized for its applications in a variety of industries, including the microelectronics industry, where it is largely used in thin film modifications in order to achieve various electronic, magnetic and structural capabilities in solid-state devices. Ta frequently forms metastable phases, including the well-known ß-phase, during the preparation of thin Ta films by standard film deposition methods such as sputtering and electro-deposition. In order to gain insight into Ta metastable phase formation, the Bain transformation mechanism is studied for Ta and the neighboring body centered cubic (bcc) transition metals in Groups 5 and …

Observation Of A Narrow Resonance Of Mass 2.46 Gev/C2 Decaying To DS*+ Π0 And Confirmation Of The D*SJ (2317) State, Dave Z. Besson, Kenneth A. Bloom, Cornell Electronic Storage Ring

Kenneth Bloom Publications

Using 13.5 fb^-1 of e⁺e^- annihilation data collected with the CLEO II detector, we have observed a narrow resonance decaying to D_s^*+π⁰ with a mass near 2.46 GeV/c². The search for such a state was motivated by the recent discovery by the BaBar Collaboration of a narrow state at 2.32 GeV/c², the D_sJ^*(2317) ⁺, that decays to D_s⁺ π⁰. Reconstructing the D_s⁺ π⁰ and D_s^*+ π⁰ final states in CLEO data, we …

Anisotropic Inflation And The Origin Of Four Large Dimensions, Christian Armendariz-Picon, Vikram Duvvuri

Physics - All Scholarship

In the context of (4+d)-dimensional general relativity, we propose an inflationary scenario wherein 3 spatial dimensions grow large, while d extra dimensions remain small. Our model requires that a self-interacting d-form acquire a vacuum expectation value along the extra dimensions. This causes 3 spatial dimensions to inflate, whilst keeping the size of the extra dimensions nearly constant. We do not require an additional stabilization mechanism for the radion, as stable solutions exist for flat, and for negatively curved compact extra dimensions. From a four-dimensional perspective, the radion does not couple to the inflaton; and, the small amplitude of the CMB …

Design And Analysis For Melt Casting Metallic Fuel Pins Incorporating Volatile Actinides: Quarterly Progress Report 5/16/03- 8/15/03, Yitung Chen, Randy Clarksean, Darrell Pepper

Fuels Campaign (TRP)

The analysis of mold filling and solidification continues with progress being made for the consideration of these two features within one model. Analysis of the induction heating process of an Induction Skull Melter (ISM) is under study. Efforts are underway to validate the modeling procedure and specific comparisons are being made to previously published work. Few detailed modeling results have been reported by other researchers, making the validations an important part of the overall modeling process. Skin heating depths, power deposition rates, and other process parameters are being evaluated for use in upcoming furnace design simulations. Efforts are beginning on …

First-Principles Calculations For Nitrogen-Containing Single-Walled Carbon Nanotubes, James P. Lewis, Mingwen Zhao, Yueyugan Xia, Ruiqin Zhang

Faculty Publications

We present calculations for possible configurations of nitrogen-containing single-walled carbon nanotubes and their electronic properties obtained with the ab initio tight-binding FIREBALL method. It is found that nitrogen atoms can be energetically incorporated into the carbon network in three forms: Substitution, substitution with formation of a vacancy structure, and chemical adsorption. The different forms exhibit different local densities of states near the Fermi levels, which might suggest a potential method to control the electronic properties of nitrogen-doped carbon nanotubes

High-Field Measurements Of Electron Decoherence Time In Metallic Nanowires: Switching Off Magnetic Impurity Spins, P. Mohanty, Richard A. Webb

Faculty Publications

We report low-temperature measurements of electron decoherence time in a series of pure gold wires, 18 nm thick and 30 nm wide. At fields up to 15 T, large enough to polarize any concentration of magnetic impurity spins, conductance fluctuation measurements show almost no temperature dependence of the decoherence time below 300 mK, both in the correlation field for interference and the root-mean-square value of the fluctuations. Combined with previous low-field weak localization measurements on samples from similar material, our experiment suggests that the ubiquitous saturation of decoherence time in these samples is not due to any mechanism based on …

Thermodynamics And Kinetics Of Defects At Surfaces, Tianjiao Zhang

Doctoral Dissertations

Fundamental understanding of the various electronic and structural properties at surfaces is a prerequisite for improved control of nanometer-scale patterning of surfaces for potential technological applications. In this dissertation, we have used multi-scale theoretical approaches to investigate the thermodynamic and kinetic properties of a few elemental types of surface defects. The multi-scale approaches range from first-principles calculations within density functional theory to empirical embedded atom method (EAM) to statistical analysis to kinetic Monte Carlo simulations. In studying the thermodynamic properties of intrinsic line defects on a vicinal TaC(910) surface, our Monte Carlo simulations in comparison with scanning tuning microscope (STM) …

Competition Between Ferromagnetism And Antiferromagnetism In Fept, G. Brown, B. Kraczek, A. Janotti, T. C. Schulthess, G. M. Stocks, Duane D. Johnson

Duane D. Johnson

Ni/Fe/Co/Cu(100) films were epitaxially grown and investigated by photoemission electron microscopy. The magnetic correlation of the Ni and Co films was investigated by element-specific domain images. We found that the Ni magnetization exhibits a continuous rotation in the spin reorientation transition (SRT) region and that the Ni SRT thickness oscillates with the Fe film thickness.

Reply To Comment On “Mev Magnetosheath Ions Energized At The Bow Shock” By J. Chen, Ta Fritz, And Rb Sheldon, S. Chang, J. D. Scudder, K. Kudela, Harlan E. Spence, J. F. Fennell, R. P. Lepping, R. P. Lin, C. T. Russell

Physics & Astronomy

No abstract provided.

Dielectric Permittivity And Electric Modulus In Bi2ti4o11, Jianjun Liu, Chun-Gang Duan, Wei-Guo Yin, Wai-Ning Mei, Robert W. Smith, John R. Hardy

Physics Faculty Publications

Frequency and temperature dependences of dielectric permittivity and electric modulus of pure and Ba-doped Bi2Ti4O11 were studied in the ranges of 1021–106 Hz and 2150–350 °C, respectively. We found that the antiferroelectric phase transition temperature of Bi2Ti4O11 decreases with Ba doping. In the permittivity studies, we also observed dielectric relaxation peaks shift to higher temperature with increasing frequency. Furthermore, in the electric modulus formalism, conducting peaks were uncovered above 150 °C in addition to the dielectric relaxation peak. We discussed the mechanisms for the dielectric relaxation and conduction processes based on TiO6 octahedra distortion and a space-charge model.

Dynamic Nonlinear Effect On Lasing In A Random Medium, Boyang Liu, Alexey Yamilov, Yong Ling, Junying Xu, Hui Cao

Physics Faculty Research & Creative Works

We have studied both experimentally and numerically the dynamic effect of nonlinearity on lasing in disordered medium. The third-order nonlinearity not only changes the frequency and size of lasing modes, but also modifies the laser emission intensity and laser pulse width. When the nonlinear response time is longer than the lifetime of the lasing mode, the nonlinearity changes the laser output through modifying the size of the lasing mode. When the nonlinear response is faster than the buildup of the lasing mode, positive nonlinearity always extracts more laser emission from the random medium due to the enhancement of single particle …

Role Of The Ground State In Electron-Atom Double Ionization, Stephenie J. Jones, Don H. Madison

Physics Faculty Research & Creative Works

Recently, absolute measurements have been reported for double ionization of helium by 5.6 keV electron-impact. At this high energy, one would think that the first Born approximation for the interaction of the projectile with the atom would be valid. However, on the basis of a lowest-order implementation of a Faddeev-type approach, Berakdar concluded that the approximation was not valid. Here we argue that (i) it is valid at this energy and (ii) the previous discrepancy between calculations in the first Born approximation and the overall magnitude of the measurements was due to a poor description of the ground state.

Effect Of Kerr Nonlinearity On Defect Lasing Modes In Weakly Disordered Photonic Crystals, Boyang Liu, Alexey Yamilov, Hui Cao

Physics Faculty Research & Creative Works

We studied the effect of Kerr nonlinearity on lasing in defect modes of weakly disordered photonic crystals. Our time-independent calculation based on self-consistent nonlinear transfer matrix method shows that Kerr nonlinearity modifies both frequencies and quality factors of defect modes. We also used a time-dependent algorithm to investigate the dynamic nonlinear effect. Under continuous pumping, the spatial sizes and intensities of defect lasing modes are changed by Kerr nonlinearity. Such changes are sensitive to the nonlinear response time.

Dielectric Permittivity And Electric Modulus In Bi2Ti4O11, Jianjun Liu, Chun-Gang Duan, Wai-Ning Mei, R. W. Smith, John R. Hardy

John R. Hardy Papers

Frequency and temperature dependences of dielectric permittivity and electric modulus of pure and Ba-doped Bi₂Ti₄O₁₁ were studied in the ranges of 10^-1–10⁶ Hz and -150–350 °C, respectively. We found that the antiferroelectric phase transition temperature of Bi₂Ti₄O₁₁ decreases with Ba doping. In the permittivity studies, we also observed dielectric relaxation peaks shift to higher temperature with increasing frequency. Furthermore, in the electric modulus formalism, conducting peaks were uncovered above 150 °C in addition to the dielectric relaxation peak. We discussed the mechanisms for the dielectric relaxation and …

The Spectra Of Type Ii Cepheids. I. The Hα Line In Short-Period Stars, Edward G. Schmidt, Kevin M. Lee, Dale Johnston, Peter R. Newman, Stephanie A. Snedden

Edward Schmidt Publications

We present 88 Hα profiles for 24 pulsating variable stars with periods between 1 and 3 days in order to explore the behavior of this line in type II as compared with classical Cepheids. Surprisingly, large velocity differences were found between Hα and the metal lines in some type II Cepheids. Strong emission was observed in three stars, VZ Aql, NW Lyr, and V439 Oph, while line filling by incipient emission is present in seven others. All of the stars with emission and most with incipient emission belong to Diethelm's AHB2 class, and the emission is associated with the secondary …

Density Of Resonant States And A Manifestation Of Photonic Band Structure In Small Clusters Of Spherical Particles, Alexey Yamilov, Hui Cao

Physics Faculty Research & Creative Works

We introduce a numerical recipe for calculating the density of the resonant states of the clusters of dielectric spheres. Using truncated multipole expansions (generalized multisphere Mie solution) we obtain the scattering matrix of the problem. By introducing an infinitesimal absorption in the spheres we express the dwell time of the electromagnetic wave in terms of the elements of the scattering matrix. Using the parameters in recent light localization experiments [Phys. Rev. Lett. 87, 153901 (2001)], we demonstrate that the density of the resonant states, related to the dwell time, shows the formation of the photonic band structure in small clusters …

Mononuclear N3S(Thioether)-Ligated Copper(Ii) Methoxide Complexes: Synthesis, Characterization, And Hydrolytic Reactivity, Kyle J. Tubbs, Amy L. Fuller, Brian Bennett, Atta M. Arif, Lisa M. Berreau

Physics Faculty Research and Publications

Mononuclear copper(II) methoxide complexes supported by N₃S(thioether) chelate ligands having two internal hydrogen bond donors have been prepared, comprehensively characterized, and evaluated for hydrolytic reactivity.

Dramatic Nondipole Effects In Low-Energy Photoionization: Experimental And Theoretical Study Of Xe 5s, Oliver Hemmers, Renaud Guillemin, E. P. Kanter, B. Krassig, Dennis W. Lindle, S. H. Southworth, R. Wehlitz, J. Baker, A. C. Hudson, M. Lotrakul, D. Rolles, Wayne C. Stolte, I. Tran, A. Wolska, S. Yu, M. Ya Amusia, K. T. Cheng, L. V. Chernysheva, W. R. Johnson, S. T. Manson

Environmental Studies Faculty Publications

The Xe 5s nondipole photoelectron parameter γ is obtained experimentally and theoretically from threshold to ∼200  eV photon energy. Significant nondipole effects are seen even in the threshold region of this valence shell photoionization. In addition, contrary to previous understanding, clear evidence of interchannel coupling among quadrupole photoionization channels is found.

Dose Coefficients For Radionuclides Produced In A Spallation Neutron Source, John P. Shanahan

Transmutation Sciences Physics (TRP)

Internal and external dose coefficient values have been calculated for 14 anthropogenic radionuclides which are not currently presented in Federal Guidance Reports No. 11, 12, and 13 or Publications 68 and 72 of the International Commission on Radiological Protection. Internal dose coefficient values are reported for inhalation and ingestion of 1 μm and 5 μm particulates along with the f1 values and absorption types for the adult worker. Internal dose coefficient values are also reported for inhalation and ingestion of 1 μm particulates as well as the f1 values and absorption types for members of the public. Additionally, external dose …

Three-Dimensional Nonlinear Evolution Ofequatorial Ionospheric Spread-F Bubbles, M. J. Keskinen, S. L. Ossakow, Bela G. Fejer

Bela G. Fejer

[1] Using numerical simulation techniques, we present the first study of the three-dimensional nonlinear evolution of an equatorial spread-F bubble. The background ionosphere used to initialize the bubble evolution is computed using a time-dependent first-principles equatorial plasma fountain model together with a prereversal enhancement vertical drift model. We find that finite parallel conductivity effects slow down both the linear and nonlinear bubble evolution compared to the two-dimensional evolution. In addition we find that bubble-like structures with extremely sharp density gradients can be generated off the equator at equatorial anomaly latitudes in agreement with recent observations.

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 …