Digital Commons Network^™

Four-Wave Mixing And Optical Phase Conjugation In Vertical Cavity Surface Emitting Devices, Gregory J. Vansuch

Theses and Dissertations

Four-wave mixing (FWM), a nonlinear optical process, was investigated in resonant cavity light emitting diodes (RCLEDs) and vertical cavity surface emitting lasers (VCSELs) below lasing threshold. These semiconductor photonic devices consisted of an optical gain region of quantum wells sandwiched between two distributed Bragg reflector (DBR) mirrors. Pump and probe lasers were injected into the devices to generate FWM. The dependence of FWM on bias current, pump laser power, and spectral and spatial separation between pump and probe lasers was investigated experimentally. A computer model of FWM based on the wave and carrier density equations was developed and agreed well …

Matching Numerical Simulations To Continuum Field Theories: A Lattice Renormalization Study, J Borrill, M. Gleiser

Dartmouth Scholarship

The study of nonlinear phenomena in systems with many degrees of freedom often relies on complex numerical simulations. In trying to model realistic situations, these systems may be coupled to an external environment which drives their dynamics. For nonlinear field theories coupled to thermal (or quantum) baths, discrete lattice formulations must be dealt with extreme care if the results of the simulations are to be interpreted in the continuum limit. Using techniques from renormalization theory, a self-consistent method is presented to match lattice results to continuum models. As an application, symmetry restoration in ϕ4 models is investigated.

Inner-Shell Excitation Spectroscopy Of Closo-Carboranes, Adam P. Hitchcock, Stephen G. Urquhart, Alex T. Wen, A. L. David Kilcoyne, Tolek Tyliszczak, Eckart Rühl, Nobuhiro Kosugi, John D. Bozek, James T. Spencer, David N. Mcilroy, Peter A. Dowben

Peter Dowben Publications

Oscillator strength spectra in the region of B 1s and C 1s excitation of three isomeric carborane cage compounds [closo-1,2-orthocarborane, closo-1,7-metacarborane, closo-1,12-paracarborane (C₂B₁₀H₁₂)] have been derived from inner-shell electron energy loss spectra (ISEELS) recorded under electric dipole-scattering conditions. Total ion yield spectra recorded at high resolution with synchrotron radiation are also reported. The spectral features are assigned on the basis of comparisons with spectral predictions derived from the results of ab initio and semiempirical (extended Hückel) molecular orbital calculations. The isomeric and core level variations in the discrete core excitations …

Electron-Impact Ionization Cross Sections Of Atmospheric Molecules, Y.-K. Kim, W. Hwang, N. M. Weinberger, M. A. Ali, M. Eugene Rudd

M. Eugene Rudd Publications

A theoretical model for electron-impact total ionization cross sections, which has been found to be reliable for a wide range of molecules, is applied to molecules of interest to atmospheric science. The new theory, the binary-encounter-Bethe (BEB) model, combines the binary encounter theory and the Bethe theory for electron-impact ionization, and uses simple theoretical data for the ground state of the target molecule, which are readily available from molecular structure codes. Total ionization cross sections of 11 molecules, CS, CS₂, COS, CH₄, H₂S, NH₃, NO₂, N₂O, O_{3 …}

Lithium Bonding Interaction In H2Cy⋯Lif (Y=O,S) Complexes: A Theoretical Probe, Salai Cheettu Ammal, P. Venuvanalingam, S. Pal

Faculty Publications

Ab initio calculations at 6-31++G(d,p) level have been done on H2CY⋯LiF (Y=O,S) complexes choosing ten possible orientations in each complex. The effect of correlation on complex binding energies has been studied via single point MP2 (full) calculations done on 6-31++G(d,p) geometry. Binding energies have been corrected for basis set superposition error. Frequency calculations confirm that H2CO⋯LiF and H2CS⋯LiF complexes have three and two stable forms, respectively. The most stable form in each complex has been found to have a strong lithium bonding interaction and a secondary hydrogen bondinginteraction. NBO analysis has revealed that in this form oxygen donates nσ lone …

A System For Collecting Milligram Quantities Of Cloud Condensation Nuclei, Darryl J. Alofs, Donald E. Hagen, Steven D. Medley, Daniel R. White, John L. Schmitt, Allen L. Williams

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An Experimental System to Collect Cloud Condensation Nuclei (CCN) Onto Filters in Amounts Sufficient for Chemical Analysis is Described. This Experimental Apparatus is Designed to Process Ambient Air at a Rate of More Than 1 M3/min. Two Identical Systems Have Been Built. One is Installed in a Laboratory at Rolla, MO. the Other is Installed on an 11 M Long Trailer. the System Isolates Three Size Classes of CCN, Having Mass Median Diameters of 0.27, 0.12, and 0.075 Μm, Respectively, and Mass Collection Rates of 11.5, 1.28, and 0.13 Mg/day, Respectively. the above Sizes and Collection Rates Are Obtained from …

The Zeus Leading Proton Spectrometer And Its Use In The Measurement Of Elastic Ρ0 Photoproduction At Hera, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. R. Okrasiński, J. Repond, R. Stanek, R. L. Talaga, H. Zhang, Margarita C. K. Mattingly, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, P. Bruni, G. Cara Romeo, G. Castellini, M. Chiarini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti

Faculty Publications

The differential cross section dσ/dt for elastic ρ0 photoproduction, γp → ρ0ρ (ρ0 → π+π-), has been measured in ep interactions at HERA. The squared four-momentum exchanged at the proton vertex, t, has been determined directly by measuring the momentum of the scattered proton using the ZEUS Leading Proton Spectrometer (LPS), a large scale system of silicon micro-strip detectors operating close to the HERA proton beam. The LPS allows the measurement of the momentum of high energy protons scattered at small angles with accuracies of 0.4% for the longitudinal momentum and 5 MeV for the transverse momentum. Photoproduction of ρ0 …

Measurement Of Inelastic J/Ψ Photoproduction At Hera, J. Breitweg, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R. L. Talaga, R. Yoshida, H. Zhang, Margarita C. K. Mattingly, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti

Faculty Publications

No abstract provided.

Study Of Photon Dissociation In Diffractive Photoproduction At Hera, J. Breitweg, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R. L. Talaga, R. Yoshida, H. Zhang, Margarita C. K. Mattingly, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti

Faculty Publications

Diffractive dissociation of quasi-real photons at a photon-proton centre of mass energy of W ≈ 200 GeV is studied with the ZEUS detector at HERA. The process under consideration is γp → XN, where X is the diffractively dissociated photon system of mass MX and N is either a proton or a nucleonic system with mass MN < 2 GeV. The cross section for this process in the interval 3 < MX < 24 GeV relative to the total photoproduction cross section was measured to be σDpartial/σtot = 6.2 ± 0.2(stat) ± 1.4(syst)%. After extrapolating this result to the mass interval of mφ2 < MX2 < 0.05W2 and correcting it for proton dissociation, the fraction of the total cross section attributed to single diffractive photon dissociation, γp → Xp, is found to be σSD/σtot = 13.3 ± 0.5(stat) ± 3.6(syst)%. The mass spectrum of the dissociated photon system in the interval 8 < MX < 24 GeV can be described by the triple pomeron (IP IP IP) diagram with an effective pomeron intercept of αIP(0) = 1.12 ± 0.04(stat) ± 0.08(syst). The cross section for photon dissociation in the range 3 < MX < 8 GeV is significantly higher than that expected from the triple pomeron amplitude describing the region 8 < MX < 24 GeV. Assuming that this discrepancy is due to a pomeron-pomeron-reggeon (IP IP IR) term, its contribution to the diffractive cross section in the interval 3 < MX < 24 GeV is estimated to be fIP IP IR = 26 ± 3(stat) ± 12(syst)%. © Springer-Verlag 1997.

Comparison Of Zeus Data With Standard Model Predictions For E+P → E+X Scattering At High X And Q2, J. Breitweg, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R. L. Talaga, R. Yoshida, H. Zhang, Margarita C. K. Mattingly, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti

Faculty Publications

Using the ZEUS detector at HERA, we have studied the reaction e+p → e+X for Q2 > 5000 GeV2 with a 20.1 pb-1 data sample collected during the years 1994 to 1996. For Q2 below 15000 GeV2, the data are in good agreement with Standard Model expectations. For Q2 > 35000 GeV2, two events are observed while 0.145 ± 0.013 events are expected. A statistical analysis of a large ensemble of simulated Standard Model experiments indicates that with probability 6.0%, an excess at least as unlikely as that observed would occur above some Q2 cut. For x > 0.55 and y > 0.25, four …

Reflections On The Gao Report On The Nuclear Triad, David W. Hafemeister

Physics

Senate Hearings on the GAO report on the nuclear triad and on the START treaty showed that vulnerabilities of the U.S. triad were vastly over‐stated, that the performance of new projected strategic systems was over‐estimated, and that the performance of existing U.S. strategic systems was under‐estimated. These exaggerations enhanced the psychological (Freud) aspects of the Cold War and compromised logic (Newton).

With the end of the Cold War it is imperative that we re‐examine the basic premises that guided the choices of the strategic nuclear systems. The initial bottom line is that these systems were successful in that they did …

Three-Dimensional Direct Simulation Monte Carlo Method For Slider Air Bearings, Alejandro Garcia, W. Huang, D. B. Bogy

Faculty Publications

The direct simulation Monte Carlo (DSMC) method is used to solve the three-dimensional nano-scale gas film lubrication problem between a gas bearing slider and a rotating disk, and this solution is compared to the numerical solution of the compressible Reynolds equations with the slip flow correction based on the linearized Boltzmann equation as presented by Fukui and Kaneko [molecular gas film lubrication (MGL) method] [ASME J. Tribol. 110, 253 (1988)]. In the DSMC method, hundreds of thousands of simulated particles are used and their three velocity components and three spatial coordinates are calculated and recorded by using a hard-sphere collision …

Summing Up: Questions And Answers On The Comprehensive Test Ban Treaty, David W. Hafemeister

Physics

My experiences with the ratification of the Strategic Arms Reduction Treaty, the Threshold Test Ban Treaty, and the Conventional Armed Forces in Europe Treaty have led me to conclude that presenting technical issues early in the process greatly reduces their politicization during the ratification end game. This chapter summarizes the important issues that will be raised during the debate on ratification of the Comprehensive Test Ban Treaty. It uses a compact question and answer format to cover the following topics: I. Nuclear Proliferation, II. Nuclear Arms Control, III. Warhead Reliability and Yield for National Security, IV. Warhead Safety, V. Verification, …

A Child's Flashlight And Rc Circuit Concepts, Matthew J. Moelter, Rand S. Worland

Physics

No abstract provided.

Harmonic Oscillation In The Presence Of Multiple Damping Forces, Chris Pelto '97

Honors Projects

The relatively mundane damped harmonic oscillator is found to exhibit interesting motion once under the influence of both a velocity dependent and a Coulombic frictional damping force. Data for the decay of the amplitude as a function of time were collected on a specially prepared torsional oscillator. with a variable electromagnetic damping mechanism. An analytical solution of the appropriate equation of motion was obtained by the method of Laplace transforms. In both the limits of zero Coulombic friction and zero velocity damping, the solution reduces to the well-known answers to the problem. the solution, when plotted with the correct parameters, …

Droplet Concentration And Size Distribution In Haze And Fog, Josef Podzimek

Physics Faculty Research & Creative Works

Fog (haze) droplet concentrations and size distributions were measured at five sampling sites representing rural and urban regions and a highly polluted marine-urban environment. Droplet imprints in a thin gelatine layer were evaluated and compared to the measurement by light scattering instruments. This enabled conditions for the application of the logarithmic-normal size distribution and for the classification of typical fog droplet size distributions to be established. In particular, the parameters featuring the width and asymmetry of a size distribution were suggested and calculated. Advantages and drawbacks of the applied droplet sampling and evaluation technique are discussed in more detail. © …

Electromagnetic Reaction Cross Sections In Relativistic Heavy Ion Collisions, Jack Dostal

Presidential Scholars Theses (1990 – 2006)

The goal of this project was to produce a computer program to predict the cross section of relativistic heavy ion collisions between given projectile and target nuclei. An explanation of the usefulness of relativistic heavy ion collision analysis is presented. The use of the Weiszacker-Williams method of virtual quanta for enhancing reaction cross sections of this type is discussed. Quantum-mechanical corrections to the semiclassical Weiszacker-Williams method are introduced. C++ computer code has been developed to calculate both semiclassical (as a check) and quantum-mechanical cross sections for these types of reactions. Preliminary results are given for the heavy ion reaction ( …

The Interaction Of Naphthoquinones With The Calcium Release Channel Of Skeletal Muscle Sarcoplasmic Reticulum, Ruohong Xia

Dissertations and Theses

The sarcoplasmic reticulum (SR) is an intracellular membrane system which regulates cytoplasmic calcium concentration in muscle and controls the contractile state of muscle. In this thesis, the interaction between naphthoquinone and the Ca²⁺ release mechanism of SR is described. 1,4-naphthoquinone (1,4NQ) is shown to stimulate Ca²⁺ release and to modify high-affinity ryanodine binding to skeletal muscle sarcoplasmic reticulum. The interaction between 1,4NQ and the SR involves the oxidation ofcritical sulfhydryl groups associated with the Ca²⁺ release mechanism. The modulation of ryanodine binding by 1,4NQ is biphasic. At low concentrations of 1,4NQ (<10 >μM) ryanodine binding is stimulated, …

Turbulence Modeling Of The Toroidal Wall Heat Load Due To Shear Flows Over Cavities In The Neutral Gas Blanket Divertor Regime, George Vahala, Linda L. Vahala, Joseph Morrison

Electrical & Computer Engineering Faculty Publications

Heat loads to the target plate in reactor tokamaks are estimated to be orders of magnitude higher than those that can be withstood by known materials. In regimes of plasma detachment, there is strong evidence that plasma recombination occurs near the divertor plate, leading to a cold neutral gas blanket. Because of the strong coupling between the plasma and the neutrals within the divertor region, there is significant neutral flows along field lines up to Mach 1.2 and Reynolds numbers over 1000. The effects of three dimensional (3D) neutral turbulence within the gas blanket on heat deposition to the toroidal …

Velocity–Space Drag And Diffusion In A Model, Two-Dimensional Plasma, Mark Anthony Reynolds, B.D. Fried, G.J. Morales

Publications

The quasilinear fluctuation integral is calculated for a two-dimensional, unmagnetized plasma ~composed of charged rods!, and is expressed in terms of Fokker–Planck coefficients. It is found that in two dimensions, the enhanced fluctuations generated by fast electrons lead to anomalously large transport coefficients. In particular, the effect of a small population of fast electrons is only weakly dependent on their density. In three dimensions, the effect of fast electrons is masked by the dominant approximation, but higher-order terms describe processes similar to those in two dimensions, and these terms can become significant for weakly stable plasmas. The differences between two …

How Much Of The Nucleon Spin Is Carried By Glue?, Ian Balitsky, Xiangdong Ji

Physics Faculty Publications

We estimate in the QCD sum rule approach the amount of the nucleon spin carried by the gluon angular momentum: the sum of the gluon spin and orbital angular momenta. The result indicates that gluons contribute at least one half of the nucleon spin at the scale of 1GeV².

Ionization Of Helium In The Attosecond Equivalent Light Pulse Of 1 Gev/Nucleon U⁹²⁺ Projectiles, R. Moshammer, W. Schmitt, J. Ullrich, H. Kollmus, A. Cassimi, R. Dörner, O. Jagutzki, R. Mann, Ronald E. Olson, H. T. Prinz, H. Schmidt-Böcking, L. Spielberger

Physics Faculty Research & Creative Works

Single and double ionization of helium by 1 GeV/nucleon U92+ impact was explored in a kinematically complete experiment. The relativistic ion generates a subattosecond (10−18s) superintense (I > 1019W/cm2) electromagnetic pulse, which is interpreted as a field of equivalent photons (Weizsäcker-Williams method). Cross sections, the emission characteristics of ions and electrons as well as momentum balances, are quantitatively discussed in terms of photoionization of the atom in this broadband, ultrashort virtual photon field. © 1997 The American Physical Society.

Search For Lepton Flavor Violation In Ep Collisions At 300 Gev Center Of Mass Energy, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. R. Okrasiński, J. Repond, R. Stanek, R. L. Talaga, H. Zhang, Margarita C. K. Mattingly, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, P. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti, G. Levi

Faculty Publications

Using the ZEUS detector at the HERA electron-proton collider, we have searched for lepton flavor violation in ep collisions at a center-of-mass energy (√s) of 300 GeV. Events of the type e + p → ℓ + X with a final-state lepton of high transverse momentum, ℓ = μ or τ, were sought. No evidence was found for lepton flavor violation in the combined 1993 and 1994 data samples, for which the integrated luminosities were 0.84 pb-1 for e-p collisions and 2.94 pb-1 for e+p collisions. Limits on coupling vs. mass are provided for leptoquarks and R-parity violating squarks. For …

Measurement Of Elastic J/Ψ Photoproduction St Hera, J. Breitweg, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R. L. Talaga, R. Yoshida, H. Zhang, Margarita C. K. Mattingly, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti

Faculty Publications

The reaction γ p → J/ψ p has been studied in ep interactions using the ZEUS detector at HERA. The cross section for elastic J/ψ photoproduction has been measured as a function of the photon-proton centre of mass energy W in the range 40 < W < 140 GeV at a median photon virtuality Q2 of 5 × 10-5 GeV2. The photoproduction cross section, σγp→J/ψp, is observed to rise steeply with W. A fit to the data presented in this paper to determine the parameter δ in the form σγp→J/ψp α Wδ yields the value δ = 0.92±0.14±0.10. The differential cross section dσ/d|t| is presented over the range |t| < 1.0 GeV2 where t is the square of the four-momentum exchanged at the proton vertex. dσ/d|t| falls exponentially with a slope parameter of 4.6 ± 0.4-0.6+0.4 GeV-2. The measured decay angular distributions are consistent with s-channel helicity conservation. © Springer-Verlag 1997.

Three-Body Models Of Electron-Hydrogen Ionization, Stephenie J. Jones, Don H. Madison, Dmitry A. Konovalov

Physics Faculty Research & Creative Works

In this paper, we report calculations of electron-hydrogen ionization whereby the final-state wave Function is approximated by recently reported analytical three-body wave functions. In a first model we use the wave function of Alt and Mukhamedzhanov [Phys. Rev. A 47, 2004 (1993)], and in a second model we use the wave function of Berakdar [Phys. Rev. A 53, 2314 (1996)].

Damped Diocotron Quasi-Modes Of Non-Neutral Plasmas And Inviscid Fluids, S. Neil Rasband, Ross L. Spencer

Faculty Publications

Computations of damped diocotron oscillations (quasi-modes) are described for non-neutral plasmas and inviscid fluids. The numerical method implements a suggestion made by Briggs, Daugherty, and Levy some 25 years ago [Phys. Fluids 13, 421 (1970)] to push the branch line that forms the continuum into the complex w-plane by solving the mode equation in the complex r-plane. For the special case of power-law density profiles the calculation finds the same quasi-mode frequencies found recently by Corngold [Phys. Plasmas 2, 620 (1995)]. It is found that the feature of the continuum eigenfunctions which indicates the presence of a nearby quasi-mode is …

Modeling And Simulation Of Optical Characteristics Of Microelectromechanical Mirror Arrays, Peter C. Roberts

Theses and Dissertations

MEMS (Micro-Electro-Mechanical Systems) micromirror devices can be used to control the phase of a propagating light wavefront, and in particular to correct aberrations that may be present in the wavefront, due to either atmospheric turbulence or any other type of fixed or time and space varying aberrations. In order to shorten the design cycle of MEMS micromirror devices, computer software is developed to create, from MEMS micromirror device design data, a numerical model of the MEMS device. The model is then used to compute the far field diffraction pattern of a wavefront reflected from the device, and to predict the …

Lower And Upper Bounds On Internal-Wave Frequencies In Stratified Rotating Fluids, Benoit Cushman-Roisin

Dartmouth Scholarship

According to classical theories, the frequencies of internal-gravity waves in stratified rotating fluids must lie between the Brunt-Väisälä frequency (a measure of the vertical density stratification) and the Coriolis frequency (equal to twice the rotation rate about the vertical axis). It is shown here that, in the case of the Earth's rotation where the pole-to-pole axis of rotation is almost everywhere not parallel to the local vertical, the range of realizable frequencies is broader. New formulas are derived for the lower and upper bounds of the frequencies.

Selective Excitation And Structure In The Continuum, C. E. Carroll, Foek T. Hioe

Physics Faculty/Staff Publications

We show that efficient transfer of molecules or atoms from one bound state to another is possible via the continuum in some cases, using two overlapping laser pulses. The structure of the continuum determines the pulse delay, laser frequencies, and laser intensities that should be used. We present simple formulas that relate the optimum values of pulse intensities, pulse separation, and detuning; these estimates can be used as a guide. More detailed calculations give quantitative results for two specific potentials.

An Inline Optical Electron Polarimeter, K. W. Trantham, Timothy J. Gay, R. J. Vandiver

Timothy J. Gay Publications

The design and operation of a simple inline optical electron polarimeter is presented. It is based on exchange excitation of ground state neon atoms. The electron polarization is determined from the degree of circular polarization of the subsequent 2p⁵3p ³D₃→2p⁵3s ³P₂ (6402 Å) fluorescence. This device can characterize both longitudinally and transversely polarized electron beams in a nondestructive fashion, and is inexpensive and easily constructed.