Vortex Motion in Niobium Thin Films

Jesse Young, Prof. Joseph Amato, Colgate University

In the mixed state of a superconductor, magnetic flux penetrates the superconductor in quantized bundles called vortices. A vortex is a small cylindrical region where the metal returns to its normal conducting state. A current sent across a thin film will induce the vortices to move, inducing power loss and heating. Using an atomic force microscope, it is possible to create a periodic array of pinning sites to study vortex

The Effects of Mechanical Strain on Mesoscopic Bismuth Thin Films

Steven A. Waldauer, State University of New York at Buffalo

A prior research project at Michigan State University, involving thin bismuth films, found that the electrical resistance of the films seemed to vary with an applied mechanical strain. Furthermore, this effect seemed to increase as temperatures decreased. This current project, began as an REU program at Michigan State, intends to further explore this phenomenon in detail.

The current stages this project involves sample production and the continuing experimentation of samples at decreasing temperatures. Bismuth film samples are produced using a photolithography process on a glass substrate. Each bismuth pattern is a few microns wide and about 100 to 150 angstroms thick. Piezoelectric wafers provide mechanical strain. Samples are glued to the wafer using vacuum grease, and the entire sample is cooled in a cryostat. Commercial strain gages are used for calibration. Resistance measurements are collected electronically using standard four terminal measurements and data acquisition software.

Future experimentation will provide more precise measurements of the effects of applied strain on measured resistance as well as determine the temperature at which this effect is maximized. It is expected that the conclusion of this project will provide a better definition of this phenomenon as well as a possible physical explanation.
 

Linewidth of Transitions in Mn₁₂ Acetate

Joe Loomis, Prof. M. E. Parks, Colgate University

Mn₁₂ Acetate is a ferromagnetic molecular cluster with a total spin S = 10 that exhibits quantum tunneling of its magnetic moment at low temperatures. Time domain terahertz spectroscopy is used to study the linewidth of the transition from m = 10 to m = 9 , which has an energy 300 GHz. The linewidth provides information about how the magnetic moment couples to its environment, which is important for understanding the tunneling process. I measured the linewidth to be surprisingly large (5 GHz). Possible explanations for this linewidth will be discussed.

Interface-Controlled and Diffusion-Limited Kinetics of Alloy Formation in Pb/Sn Thin Films

Anthony Clark, Prof. E. J. Cotts, Binghamton University

Thin film reactions regularly exhibit two distinct growth regimes, interface-controlled and diffusion-limited. It can be shown that after the growing alloy reaches a certain thickness, the interface-controlled kinetics will always change over to a diffusion-limited process. In this study, thermal analysis on the Pd/Sn system was performed using differential scanning calorimetry (DSC). The rate of one-dimensional intermetallic growth in our planar samples was calculated from heat flow data. In Pd/Sn (L) diffusion couples, we found that interface-controlled kinetics are sustained for an extended period of time. At longer times we observed the transition to diffusion-limited kinetics, at which point our data qualitatively agrees with previous studies. To our knowledge, this is the first time the interface-controlled growth mechanism has been so explicitly portrayed for the Pd/Sn system.

Pentacene Thin Film Field Effect Transistors

Katie Lotterhos, Binghamton University, Prof. Robert Dynes, University of California at San Diego

Research at UCSD is exploring pentacene as a possible substitute for silicon in thin film field effect transistors (FET). With fabrication possible at lower temperatures, pentacene FETS would be easier to mass produce and cheaper than silicon. Several attempts were made to develop the pentacene thin film layer. The three methods used were growing crystals by vapor phase transport, growing films via vapor phase transport, and growing films by thermal evaporation. We will discuss the methods used to fabricate a pentacene FET, results, and pathways for further research.
 
 

Feynman Diagrams in Quantum Electrodynamics

Fred Vonstein, Union College

The following independent study is an effort to understand Quantum Field Theory; the simplest of which is Quantum Electrodynamics (QED), which describes interactions between charged particles and photons. The focus of the project was to learn how to calculate Feynman Diagrams. As an exercise, Compton scattering is calculated from the Feynman Diagram method. The calculation required a background study in such topics as covariant formalism, second quantization, and S-Matrix expansion.

Solution of the "Degenerate Model" for Parafermi Particles of Order Two

Terry Tarnowsky, Prof. Charles Nelson, Binghamton University

Fundamental theories allow for the existence of types of particles other than fermions and bosons. However, there has been no experimental identification of any of these mystery particles.

Paraparticles are particles with a paraquantization order greater than 2 (p>2) which obey a generalized statistics. Normal Fermi-Dirac and Bose-Einstein statistics correspond to paraquantization order 1 (p=1). Our goal is to obtain a generalization of the normal BCS theory for the case of p=2 parafermions. As an initial step, we construct a generalization of the quasi-spin treatment of a model simpler than that used in the standard BCS theory. In particular, we have solved the "Degenerate Model" for p=2 parafermions.

An Investigation of Future CDF Measurements of W Helicity in the Decay of the Top Quark

Brock Tweedie, University of Rochester

The top quark will soon be coming under greater scrutiny at CDF with RUN II of the Fermilab Tevatron collider. I have performed an investigation that gauges CDF’s improved ability to measure the helicity of W bosons produced in the top quark’s immediate decay. This measurement provides a direct indication of the spin structure of the weak interaction in that decay. Using simulated CDF Run II data, I study the W helicity sensitivity of the top decay’s kinematic observables. Optimization of the helicity measurement via appropriate choices of observables and data cut is also addressed.

Tests of the e94 Range Stack Upgrades

Adam Rogers, Binghamton University, Dr. James Frank, Brookhaven National Laboratory

The purpose of the e787/e949 AGS experiments at Brookhaven National Laboratory is to detect the rare decay of a positive kaon into a positive pion and a neutrino-anti-neutrino pair. The new e949 experiment is expected to increase the sensitivity by about one order of magnitude. To achieve this goal, the detector is being upgraded to achieve this new desired sensitivity. One of the modifications taking place is the improvement of the energy resolution of the experiment. To accomplish this, the amount of light detected by the range stack was going to be increased by the purchase of 96 new scintillators, which were all to be tested before installation into the AGS detector. The goal was to measure the photoelectron yields with respect to position for each of the counters. The intensity with respect to position was also determined from the testing and this led to the determination of the attenuation lengths from each of the 96 scintillators. These new results were then compared to those for an old scintillator module. It was found that on average, the intensity of the modules increased considerably compared to the older module, by a factor of about 1.5 times, and the attenuation lengths increased by a factor of 2.5. These results show that the new modules are much more capable of detecting the rare kaon decays than the old modules.

Spin Correlations in Top Production and Decay at e+e- Colliders

Andrew E. Blechman, Cosmin Macesanu, Prof. Lynne H. Orr, University of Rochester

The top quark, recently discovered at Fermilab, decays before it can hadronize; this allows its spin information to be passed directly to its daughter particles. We study these spin correlations in top production and decay at electron-positron colliders, looking specifically at dilepton events. Using Monte Carlo techniques, we calculate tree-level cross sections in terms of quantities that are directly observable experimentally.
 

Cataclysmic Variables

Jessica Lavine, Union College

Cataclysmic Variable stars are binary star systems that vary in magnitude due to the transfer of gas of the red giant star on to its white dwarf counterpart. The research consisted of observing the Cataclysmic Variable DQ Herculis in order to determine its change in magnitude, and observing other major characteristics of this eclipsing binary system. I will talk about my observations as well as the further research I plan on doing. I will also illustrate important aspects of image processing for CV observational research.

Extended HI Envelopes Around Low Surface Brightness Galaxies

Diane Chin, Binghamton University, Dr. Karen O’Neil, Arecibo Observatory

Using the Arecibo Gregorian telescope, we undertook to look for extended neutral hydrogen gas around four low surface brightness galaxies in the direction of the Pegasus Cluster ([OBC97] P06-4, [OBC97] P04-1, [OBC97] P06-1, & [OBC97] P02-3). Although uncertainties in the beam pattern made final analysis of the data difficult, three of the galaxies observed appear to have HI gas extending 2-5 times farther than the optical (d₂₇) diameter of the galaxies. Additionally, all three cases show the HI distribution to be fairly lopsided.

Image Analysis for the Peculiar Virgo Cluster Galaxy NGC 4383

Holly Burnside, Union College

In the 1920s, Edwin Hubble started categorizing the galaxies he observed according to their morphology (appearance), which may be linked in some way to their evolutionary history. He placed galaxies into two main classes: spiral and elliptical. His classification is still widely recognized by astronomers today. There are, however, many galaxies that do not fit into Hubble's categories, particularly galaxies in crowded environments. NGC 4383, located in the Virgo Cluster, roughly 16 Mpc (50 million light years) away, is one of these galaxies. The morphology of this galaxy was studied using optical blue, green, red, and Ha-line emission images, which were obtained at the WIYN telescope in Arizona. Optical light traces the stellar distribution of the galaxy and Ha emission is a tracer of recent formation. A Hubble Space Telescope image was used to examine the central regions of the galaxy at high resolution. The galaxy has active star formation concentrated in several large star-forming regions in the central regions and irregularities in the stellar and dust distributions. The peculiarities in this galaxy are most likely due to a gravitational interaction with another galaxy, which has perturbed the stellar and gas distributions and triggered star formation.

Pole Solutions for Koronis Family Asteroids using Sidereal Photometric Astrometry

Marko Krco, Prof. S. Slivan, Colgate University

According to the currently accepted theory, the Koronis Family asteroids were created through a cataclysmic disruption of a single parent body. If true, we would expect the asteroids to have "remembered" the pole axis and spin direction of the parent body in much the same way as they have retained its orbital characteristics. Previous attempts to find correlations between the pole solutions of the member asteroids were inconclusive. Our goal is to develop and implement a computational method described by Drummond (1988) to determine the pole solutions for several Koronis Family asteroids. Correlating these findings with those of previous methods should provide conclusive results.
 

Ultra-Short Pulsed Laser Diagnostics Using an S.H.G. F.R.O.G.

Eugene Torigoe, Binghamton University; Prof. Linn Van Woerkom, Ohio State University

With the development of pulsed laser systems that can create pulses on the order of femto-seconds there arises the problem of properly characterizing these pulses. Experimenters who use these systems rely on the fact that they know the widths of the pulses as well as the distribution of frequencies along the pulse known as the pulse’s chirp. A method of properly characterizing laser pulses was developed in 1993 by Rick Trebino, known as Frequency Resolved Optical Gating (F.R.O.G.). A FROG system consists of an apparatus that creates an image of the pulse on time-frequency axes, and an iterative algorithm that extracts the width of the pulse and the frequency distribution along the pulse from that image.

A Second Harmonic Generation (S.H.G.) F.R.O.G. apparatus was built and tested. The S.H.G. F.R.O.G. geometry is a particular type of FROG geometry based on a non-linear optical effect that transforms temporal information of the pulse into spatial characteristics of a signal pulse. The S.H.G. F.R.O.G. was used to characterize the laser pulses from the two 120 fs, 800 nm pulsed laser systems in the Van Woerkom lab.

Superluminal Tunneling

Mark Kostuk, Union College

We present a numerical time-dependent solution to the Schrodinger equation for the evolution of a wavepacket incident on a potential barrier and examine the mechanism behind its superluminal propagation. Several groups have recently shown that photonic pulses tunneling through a potential barrier travel at speeds greater than the speed of light. A purely quantum phenomenon, tunneling has been studied since the 1930's in the form of stationary (time-independent) solutions, but these are insufficient for our current problem. In order to examine propagation speeds time-dependant solutions are required, however the difficulty of this situation makes analytical solutions impossible. We employ computer simulations and numerical approximations to the problem of tunneling in an effort to understand this bizarre behavior of nature. Superluminal travel violates causality; it allows for an effect to occur before its cause. Our simulations show that causality is not violated due to the probabilistic nature of quantum mechanics on information transmission.

Computation and Graphical Analysis of Infinite Planar X-Ray Wave Guides

Kevin Udwary, Siena College

X-rays propagation in an infinite planar dielectric wave-guide is useful for several reasons. First, the methods developed for an infinite planar wave-guide can be applied to more difficult cases, such as cylindrical wave-guides. Second, these methods can be applied to physical systems, such as x-ray "optical" fibers or quantum computing. The motion of x-rays through both metallic and a dielectric wave-guide were shown. The energy and allowed standing wave modes of the x-rays throughout the guide were examined and represented graphically using Mathematica. The limitations of the x-ray wave-guides were examined by viewing the effect on the x-ray wave-guide modes as the physical properties of the guide, such as the height, were changed.

Single-Photon Interference Experiments

Lauren Heilig, Colgate University

We present experiments aimed at studying the wave-particle duality of light. A first set of experiments involve recording the interference of light at the single photon level by passing an attenuated laser beam through a Mach-Zender interferometer. Photon detection rates are measured as a function of the optical path length. A second set of experiments underscores the particle nature of light using parametric down-converted light.
 
 

Thermal Conductivities of Various Textiles

Chris Carroll, Siena College

In order to obtain thermal data, a cylindrical tube was constructed to serve as a uniform heat source to the textile. By placing a power circuit down the center of the metallic tube, heat is generated and presented to the textile. Using a temperature-sensitive chip, the LM35 temperature sensor, a thermometer circuit was constructed to measure energy changes inside the apparatus. The power output of the circuit can then be used to calculate the conductivity.

Pressure Phenomena Through Various Textiles

Daniel Fisher, Siena College

The phenomenon of airflow through various textiles is a new and intriguing aspect of physics that can determine the efficiency of various articles of clothing or general textiles. A time constant for pressure leak-up can be observed by generating a vacuum inside a chamber at a known pressure, and attaching the textile to an orifice on the chamber. Upon the opening of a valve, the atmospheric pressure will then attempt to distribute itself by flowing to the lower pressure region through the textile. The time needed to leak up to atmospheric pressure inside the chamber can then be interpreted to generate a time constant. Using this time constant, it is possible to determine a relationship to some already known textile constants. Some practical applications from this research could be the determination of how well some types of clothing insulate the garment wearer, or their ability to handle a large pressure difference on each side of the textile across a known surface area.

Order and Packing in a Two-Dimensional Pile of Rods

Saul Lapidus, Prof. Scott Franklin, Rochester Institute of Technology

In this talk, preliminary results on how anisometric granular materials pack, and how to quantify local and global order will be discussed. The experimental system under investigation is essentially a two-dimensional piles of rods. Granular materials pose a complex many-body problem for which much of statistical mechanics must be reworked. The general characteristics of ordinary (round) granular materials as well as rod-like (anisometric) particles will be discussed, as will future directions.

Simulating the Haystack: Modeling a 2-D Anisometric Granular Material

Kevin Stokely, Prof. Scott Franklin, Rochester Institute of Technology

Granular piles are large collections of small, discrete particles. Because the particle size is macroscopic, thermodynamic effects do not affect the particles, and the pile often fails to settle into a minimum energy state. A simulation of the settling of long, thin, two-dimensional nails will be discussed, with a focus on the effects of the particle aspect ratio (length/width) on the final order and packing fraction of the piles. Previous research in the field, an overview of the simulation, and future modifications to the simulation will be presented.

Global Warming's Effect on the Sea Level

Jeff Reardon, Siena College

Global Warming is becoming a threatening problem in today's world. Though its effects may be decades away they must be realized. The change in sea level alone will be a serious condition. Sea water expands differently in the different regions of the ocean. These regions are the arctic, subtropical, and tropical regions. Each region has a different equation on how the temperature acts at certain depths. The expansion of sea water at these depths is effected by pressure and salinity. The average depth of the ocean varies along with the volume for each region. All of these factors determine how the sea level will change due to a rise in surface temperature. The results of this will be discussed using graphs and data tables.
 
 

Optical Anisotrophy of Interacting Chromophores in Protein Complexes: Exploration of a Stochastic Theory*

Laura A. Allaire,** Prof. R. S. Knox, University of Rochester, Jennifer Dawson,*** Kent State University

Excitation transfer among light-harvesting chromophores is of critical importance to photosynthesis. The fundamental mechanism for this transfer is well known to be the interaction between Coulomb-induced transition dipole moments, but the complexity of the environment of the chromophores makes numerous approximations necessary when comparing predicted with measured results. Over the past several years both the knowledge of protein structures and the accuracy of fast optical measurements have increased to a stage at which some of these approximations may be assessed. A theory of optical anisotropy under development by Gülen and Knox [1] is intended to combine various aspects of existing stochastic theories (e. g., [2,3]) in order to address this issue. We report here preliminary calculations based on this theory for comparison with anisotropy data on C-phycocyanins [4] and peridinin-chlorophyll-protein complexes [5].

* Supported in part by USDA NRICGO grant 95-37306-2014 and NSF REU grant PHY 99-87413.

** Present address: Institute of Optics, University of Rochester, Rochester, NY 14627-0186

*** Present address: Department of Physics, Kent State University, Kent, OH 44242-0001

#R. S. Knox and D. Gülen, Photochem. Photobiol. 57, 40-43 (1993); D. Güle and R. S. Knox, in preparation.

2. H. Haken and P. Reineker, Z. Physik 249, 253-268 (1972)

3. R. Wertheimer and R. Silbey, Chem. Phys. Lett. 75, 243-248 (1980)

4. M. Debreczeny et al., J. Phys. Chem. 99, 8412-8419 and 8420-8431 (1995)

5. F. J. Kleima et al., Biophys. J. 78, 344-353 (2000)

Quantum Computation

Scott Oppenheimer, Binghamton University, Marjorie Quant, United States Air Force - Rome, NY Research Center

Using quantum probabilities for computation leads to novel and unexpected algorithms Shor’s factoring algorithm and Grover’s search algorithm are two such algorithms that are faster than their conventional peers. Using the additive nature of quantum probabilities, non-deterministic algorithms can solve exponential problems in polynomial time. The current state of the art in quantum computers (ion trap, and NMR) will also be discussed.

Probability Backflow of the Klein-Gordon Particle

John McVeigh, Prof. Shimon Malin, Colgate University

Quantum mechanics is a powerful theory of nature that sometimes produces counterintuitive results. For two superposed plane waves of certain characteristics, it can be shown that there are values of time and space that yield negative probability current. The goal of my research is to investigate the occurrences of negative probability current for the Klein-Gordon particle.

Energy States and Error Bounding for an Initial Gaussian Wavefunction in the 1-D Infinite Square Well

David Etlinger, Prof. Joseph Eberly, University of Rochester

The 1-D infinite square well (i.e., a potential that completely bounds a wavefunction to a finite interval of the real line) is a simplistic model of particle motion that nevertheless remains useful in both theory and practice. However, simplification often introduces errors that must be bounded if a model is to have any validity. Gaussian wavefunctions are often used to describe particles in traps, but the infinite extent of such functions is in conflict with the square well model, and leads to error. Given a Gaussian with an initial momentum in a square well, we have calculated an explicit expression for the expected energy states of the particle. We have then carefully bounded the errors introduced through approximations, and shown under what parameters the model is valid.