Session JF - General Poster Session.
POSTER session, Tuesday morning, November 09
Brussels/Vienna, Sheraton Chapel Hill

[JF.01] Deposition of Aligned Carbon Nanotubes via Microwave Plasma Enhanced CVD

Aligned multi-wall carbon nanotubes have been grown on substrate by the microwave plasma enhanced chemical vapor deposition technique using methane/ammonia mixtures. The concentration ratio of methane to ammonia, substrate temperature and catalyst material were varied to affect aligned carbon nanotube growth. The morphology, structure and alignment of carbon nanotubes were studied by scanning electron microscopy, transmission electron microscopy and x-ray diffraction. Both concentric and bamboo-type multi-wall carbon nanotubes were observed. Growth rate, alignment, morphology and structure of carbon nanotubes changed with methane/ammonia ratio and substrate temperature.

[JF.02] Double Crystal X-ray Diffraction Analysis of Tensile Strained GaAs Quantum Wells Grown on Relaxed InAlAs Grid Layers

A set of tensile strained quantum well structures grown via molecular beam epitaxy (MBE) on InAlAs grid layers are studied by x-ray diffraction. Strain profiles are measured using high resolution double crystal x-ray rocking curves. Full relaxation of the InAlAs grid is initially assumed as suggested by a separate transmission electron microscopy (TEM) review of the samples. Further rocking curve analysis is made for both a fully strained and fully relaxed case of the given structure using Taupin-Tagaki equations based on dynamical scattering theory. The correlation of experime and simulation results are discussed using theories of thermal dynamics.

[JF.03] Studies of Single-Walled Carbon Nanotubes Produced Under Different Growth Conditions

Single-walled carbon nanotubes can now be produced in large quantities by arc discharge, laser vaporization, and CVD techniques. The laser vaporization method provides the greatest degree of control over growth conditions and hence is the technique most suited for studying nanotubes made with different growth parameters. Such parameters include target composition, laser power, laser wavelength, furnace temperature, and the type of gas used. We are varying these systematically and will give results for end products characterized by x-ray diffraction, Raman spectroscopy, and TEM.

[JF.04] NMR Cell for the Study of Supercritical Fluid Solutions

Nuclear magnetic resonance (NMR) offers unique, highly localized molecular information. The importance of the technique is well established in studies using chemical shift, spin coupling and relaxation techniques to provide detailed structural characterization, determination of chemical equilibria-kinetics and an understanding of molecular dynamic processes. However, the wide-spread application of NMR spectroscopy to study high-pressure and supercritical fluids has been limited due to the complexity involved in the necessary instrumentation. One approach is to design a dedicated high-pressure NMR probe. Another approach involves the utilization of a high-pressure cell designed to fit in commercially available NMR probes much like a standard NMR tube. This latter approach allows the researcher to perform a broader variety of experiments since the ultimate limitation to experimental flexibility is the available probes. In the present communication we present the design and implementation of a simple, three-piece, high-pressure NMR cell constructed of high-performance polymers. The NMR cell has pressure capabilities up to 400 bar with the temperature limitations determined by the particular polymer chosen. The multinuclear NMR data presented show the utility of this cell in the study of supercritical fluid solution systems relevant to analytical separations and extractions.

[JF.05] An Experimental and Theoretical Analysis of the Multiphonon Excitation Probability for Einstein-like Modes in Atom-Surface Scattering

Atom-surface scattering and He atom scattering in particular have proven to be useful tools in investigating the properties of surface adsorbates. Inelastic scattering of He atoms is uniquely sensitive to the low energy vibrational modes of surface adsorbates. In many cases one or more of the low energy adsorbate modes appears as a dispersionless Einstein mode which produces a very characteristic series of multiquantum overtone peaks in the inelastic scattering intensity for fixed incident beam and detector positions. The probabilities of multiple excitation (multiphonon excitation) of decoupled oscillating adsorbates on a surface due to impact by an atom or molecule are developed using a theory based on the generalized temperature-dependent Poisson distribution. Comparisons are made with helium scattering results for adsorbed carbon monoxide on metal substrates. Interestingly, the simplest form of the theory with no free parameters explains the number and relative intensities of the observed multiquantum overtone peaks. The inclusion of a scattering form factor based on the hard-core interaction potential between He and CO results in a relatively simple model which correctly predicts the angular dependence of the distribution of multiphonon excitations in addition to the variation with incident energy and adsorbate frequency. The model is used to calculate the excitation probabilities of other adsorbate vibrational modes which have not yet been observed using helium scattering. The model is also applied to the case of He atom scattering from monolayer coverages of metal substrates by heavier rare gases.

[JF.06] Annealing of Amorphous Diamond-like Carbon Films Doped with Boron

Amorphous hydrogenated diamond-like carbon (DLC) films have been prepared by the saddle-field glow discharge technique. The films were doped with boron from the gas phase during the deposition. Doping with boron has been proved to be controllable and electrically effective. The samples are p-type and exhibit a thermally activated conductivity in the temperature range 300-500 K. The data on hole concentration and mobility obtained from Hall effect measurements will be presented. Changes in transport properties of the samples resulted from annealing in vacuum at different temperatures will be discussed.

[JF.07] Effect of Surface Features on the Critical Current in Single Crystal Whiskers of Doped BSCCO Superconductors

Authors: J.E. Payne, J. Obien, and J. McGee

Title: Effect of Surface Features on the Critical Current in Single Crystal Whiskers of Doped BSCCO Superconductors

Atomic force microscopy (AFM) and non-destructive electron probe microanalysis (EPMA) techniques have been utilized to examine surface features on single crystal whiskers of BSCCO materials with Ca substituted with various amounts of Y. The surface of the whiskers is decorated by features that are approximately 2 mm in diameter and vary in height. Initial analysis of the regions indicates a higher concentration of both Bi and Ca when compared with the surrounding material. Preliminary indications indicate that whiskers containing these features exhibit a larger critical current than similarly prepared samples that do not exhibit them. This suggest that these sites serve as pinning centers and might be manifestations of screw dislocations in the whiskers.

*Suport by the Department of Energy: DE-FG02-97ER45630

[JF.08] Modeling \gamma and X-ray Pulsar Spectra

Since the discovery of pulsars in 1967, their emission spectra have been a source of great study. The focus of the current research is to model the high frequency component, gamma and X-ray. The model will use a dipole magnetic field that can either be aligned or not aligned with the rotation axis and the induced electic field to establish the pulsar magnetosphere. The first goal will be to use the curvature radiation photons to calculate the rate of electron-positron production and their density. With this information, further radiation processes can be included to further describe the observed spectra.

[JF.09] Identification of High Spin States in Neutron-Rich ^113,115,117Pd Nuclei.

New band structures in neutron-rich ^113,115,117Pd nuclei have been observed by measuring prompt \gamma-rays emitted from the spontaneous fission of ^252Cf. \gamma-ray coincidence data from the Gammasphere array shows the first yrast band crossings, built on the \nu h_11/2 orbital, in ^113,115,117Pd at a frequency of \hbarømega \approx 0.47 MeV. The rotational behavior, as well as energy level properties of these bands, suggests a prolate nuclear shape. Two previously unreported positive-parity bands are also observed in ^113,115Pd, as well as significant extension of the known decay schemes of these nuclei.

[JF.10] A Source of H or D Atoms for a Charge-Exchange Ionizer

Future nuclear physics experiments planned at TUNL will require greater polarized H and D ion beam intensities. As part of a program to develop a more efficient charge-exchange ionizer for these polarized beams, we have built a simple, compact H2 (or D2) RF dissociator. This system produces unpolarized atoms and is built to mimic the flux of polarized H (or D) atoms from the present TUNL atomic beam source. For highest H2 (or D2) dissociation probability, a design was required to maintain a ~1 to 0.1 mbar discharge pressure, while minimizing the input gas flow. This reduces pumping requirements on the charge-exchange cell into which dissociated atoms are directed. Our design uses concentric pyrex tubes with water flowing between them, surrounded externally by three aluminum plates which act as capacitors. A surrounding coil between two plates supplies the 100W-200W of RF at 13.5 MHz needed to maintain the discharge. The inner pyrex tube is narrowed to a capillary at its exit end to limit the emerging flux into the teflon charge-exchange canal. Details of the dissociator and charge-exchange cell design will be provided, and measurements made showing the pressure range of stable dissociator operation will be presented.

Work supported in part by the US DOE Office of High Energy and Nuclear Physics

1. N. Koch, Diploma Thesis, Unversitat Erlangen-Nürenberg (1995).

[JF.11] Pressure Dependence of X-Ray Yield on Cooling for Crystal X-Ray Generator

The UNC crystal x-ray generator consists of a 6.5 x 3.1 x 2 mm LiTaO_3 pyroelectric crystal, whose temperature can range from 22 to 120 degrees Celsius. A SiLi detector, placed approximately 1 cm away from a target, is used to detect x-rays from both the pyroelectric crystal and a thin target of Fe evaporated on to a Cu foil. When one surface of the crystal is heated a strong electric field is produced on the other side which accelerates electrons toward the crystal producing Ta L and M x-rays. During cooling, the electric field reverses and a target x-ray spectrum is obtained. The chamber can be pumped on so that effects of gas pressure can be studied. The x-ray intensity changes with varying pressure. Repeatable measurements have been done using the x-ray generator at various low pressures ranging from ~5 to ~30 mTorr. At low pressures, the x-ray yield is relatively constant with time. As the pressure increases an initial high x-ray peak is produced which decreases rapidly with time. The most dramatic increase seen in x-ray yield peak occurs between 20 and 30 mTorr differing by 64 counts/sec and 224 counts/sec, respectively.

[JF.12] Polarization-modulated Differential Interference Contrast Microscopy

Differential interference contrast microscopy yields high-resolution images of unstained biological cells as well as semiconductor structures. Image highlights and shadows are generated by the spatial gradient of optical path at a given point in the specimen. We have improved upon this well-developed technology by inserting a liquid-crystal variable retarder into the microscope. Modulating the retarder at frame rates switched image highlights into shadows and vice versa in alternate frames. Using an image processor, alternate frames were subtracted and the difference image was displayed in "real time". In order to select the optimum retardance, we measured the signal-to-noise ratio (SNR) of the images of a standard test slide(diatom) by the cross-correlation method[1,2]. Because of depolarization by the high-NA condenser and objective lenses, SNR was optimum at ±l/20 retardance. Supported by NIH grant 1 R21 RR13358-01.

1 Bershad, HJ and Rockmore, AJ, IEEE Trans. IT 20, 112-113(1974). 2 Frank, J and Al-Ali, L, Nature 256, 376-379(1975).

[JF.13] Light scattering from Sickle Cell Hemoglobin: Polarized and Unpolarized

Sickle cell polymers form due to aggregation of a mutant form of hemoglobin (HbS). The polymerization of HbS leads to microvascular occlusion characteristic of Sickle Cell Disease. A good understanding of HbS polymerization requires a way to quantify the degree of polymerization. As our calculations show, total intensity light scattering is not always linearly dependent on the amount of polymer. Polarized light scattering has been proposed as a more accurate way to measure polymer content. We use a new modulation method to measure all 16 Mueller Matrix elements, which completely describe how the Polarization State of light is altered upon scattering. Preliminary results of light scattering measurements from spheres and hemoglobin show that the instrument works properly. In future experiments, we will attempt to use polarized light scattering as an accurate measure of polymerization. In addition, Polarized light scattering may provide information on the higher order structure of sickle polymer bundles that has not been obtainable by other means.

[JF.14] The Origin of Injuries Related to Gender Differences in Soccer Players

Previous research has shown that women soccer players suffer injuries at a much greater rate than their male counterparts. This study concentrates on damage to the anterior cruciate ligament due to hyper-extension during the change of direction while running. Comparison of male and female subjects is made through high speed video and emg signals (nerve impulses). Data from a force plate and an accelerometer allows simultaneous determination of the ground reaction forces and acceleration of the center of mass. Data are analyzed in two ways. First the emg signals are studied to compute the force to strength ratio for each of the muscles to identify stresses near the strength limit. Additional analysis through body segment calculation is in progress. In this analysis a standard model of limb and body segments adjusted for each subject is employed to determine ligament stresses from the force plate data and dynamical calculations.

[JF.15] No! ... Not another Periodic Chart of the Elements!

No, but we present important evidence for Hakala's (Hakala, J. Chem. Phys. 56, 178 (1952)) chart, which differs from standard charts in having the s elements moved upwards to periods 0 through 6. First: All periods are doubled, including length 2. Second: Secondary periodicity(D.V. Korol'kov and V.A. Latysheva, Vestnik Sankt-Peterburgskovo Univesiteta, 1998, series 4, no. 1, pg. 52) is arranged so as to occur in the same periods rather than staggered. (Secondary periodicity is seen, for example, in the differences of the atomic numbers of elements and of the elements above them.) Third and most important: This form of the periodic chart can be derived from first principles(Y.B. Rumer and A.I. Fet, Teor. Mat. Fiz. (Russ) 9, 203 (1971))(A.O. Barut, in "Structure of Matter (Proceedings of the Rutherford Cantennary Symposium, 1971)," ed. B. Wybourne, University of Canterbury Press, Canterbury, 1972, pp. 126-136)(G.V. Zhuvikin and R. Hefferlin, Symmetry Principles for Periodic Systems of Molecules, Joint Report #1, Physics Departments, Southern Adventist University and St. Petersburg University, 1994) using the boson dynamical groups of symmetry SO(4,2)XSU(2)sXSU(2)d and subgroups.

[JF.16] Excitation of High Energy Adsorbate Vibrational Modes by Atom-Surface Scattering

The surface scattering of thermal energy and hyperthermal energy rare gases heavier than He usually exhibit few quantum mechanical features such as diffraction or single phonon peaks. Instead these types of scattering events are generally classical in nature, as manifest by the fact that the Debye-Waller factor is typically negligibly small. Thus scattering of heavier rare gas atoms from clean or adsorbate covered surfaces is normally expected to produce broad multiphonon features in the energy-resolved scattered intensity. However, we show in this work that high frequency vibrational modes of surface adsorbates can produce very characteristic signature features in the observable inelastic intensity in experiments using atomic beams as scattering probes. These features consist of peaks in the inelastic background, due to multiquantum excitation of the high energy vibrational modes, and these peaks are significantly broadened by the multiphonon scattering arising from the substrate and other low energy adsorbate modes. Calculations of the scattering of rare gases from several types of adsorbates indicate that by selecting the probe projectile species and by tuning the incident energy and the incident beam angle, selected high energy modes can be excited and such experiments can be used to accurately measure the vibrational frequencies and polarizations of high energy adsorbate modes.

[JF.17] Temperature Control of Pyroelectric Crystals in X-ray Generators

Pyroelectric crystals, such as LiTaO_3, produce x-rays when heated and cooled in a fore vacuum. When the crystal is heated, using a small resistor, Ta L and M x-rays are detected. X-rays from a Cu target, however, are detected as the crystal temperature approaches room temperature, or its initial value. A LabVIEW program has been written to control and measure the crystal temperature. The Lab-NB board is used to interface the software program with a simple circuit. The combination of the software and the hardware allows for the crystal temperature to increase linearly at a requested rate, then to remain at constant temperature for any desired amount of time, and then to decrease linearly at a programmed rate. With this system, the effect of the thermal history of the crystal on x-ray yield can be studied. A Peltier cooler has been added to the set up so that a greater temperature range can be studied.

[JF.18] Infrared laser desorption and ionization mechanisms

Infrared lasers are becoming more widely used for mass analysis of biological molecules. However, the fundamental processes of IR laser desorption and ionization are poorly understood. We have used a tunable, picosecond, mid-infrared free electron laser to target specific vibrational bands of select organic materials to pinpoint these mechanisms. Calculations of laser energy deposition in solids under dense vibrational excitation suggest that desorption is initiated by a rapid phase explosion, consistent with our observations of ejecta and an intensity dependence of the signal. We have also observed that ion yield is optimized at wavelengths shifted with respect to the bulk sample absorption spectra. The timing of the ion signal suggests that the optimal ionization step occurs late in the plume expansion when the ionization rate begins to exceed the rate of collisional neutralization. Our results show that wavelength and pulse length critically affect the ion yield.

Supported by the Medical Free-Electron Laser Program of the Office of Naval Research and the Office of Science, U.S. Department of Energy.

[JF.19] Wave-Particle Duality and the Perception of Spatial-Temporal Coherence

For 1 or 2-slit interference patterns, constant phase relations (on average) must account for both synchronized movements of photons that arise from distinct Huygens wavelet sources within the slits, as well as the same phase relations (on average) of successive photons from each Huygens source - i.e. coherence must be maintained through space-time. This temporal coherence of successive photon movements cannot be explained by ``self-interaction", but, it is proposed, by successive interactions of the most probable particle trajectories across time. In this way, the product ``interference term" in the probabilistic description of 2-slit intensity could refer to successive passage of individual photons - in the absence of ``self-interaction" or ``wave-like" behavior of single photons. Preliminary results (Alkon amp; Wu, in prep) with a high frequency oscillating shutter demonstrate a classic ``smearing" with low frequency (up to 500 Hz), but a clear emergence of a discernible 2-slit interference pattern with high frequency (1-5 KHz) shutter oscillation. Rapidly alternating successive photon passage through each slit (separately) is, therefore, suggested to be required for approximate coincidence of peaks and troughs, equal numbers of photons from each slit, on average, and, therefore, bands of few or no photons at minima. For an interference pattern, a minimal ``dwell time" would be necessary to detect and integrate the accumulation of photons emanating from each slit. Thus, photons may not divide ``wave-like" at a double slit, but instead move with successive time-coherent wave trajectories that make maximal and minimal areas of intensity detectable.

[JF.20] Einstein's Gravitational Redshift (EGR) as a Possible Cause of the Hubble-Humason Redshifts (HHR)

In 1911, Einstein discussed the deformation of space by massive stars, causing gravitational redshifts and bendings of light. He found for the spectra of sun the EGR value of 2 10^-6. At those times, all redshifts observed in the spectra of stars (Huggins), of canal rays (Stark), and of mechanically propelled light sources (Majorana), were rightfully handled as due to the Doppler Effect. The sun's EGR value was therefore said equal to a Doppler shift in a runaway motion with a speed of 0.6 km/s. Thus, Hubble and Humason, too, expressed (since 1929) the HHR values in observed spectra of distant galaxies, \it"for convenience", in terms of equivalent Doppler shifts. These HHR values roughly corresponded to a runaway speed of 100 km/s per every megaparsec (Mpc) distance to a given galaxy. A Mpc is ~200 billion a.u. (astronomical units), where an a.u. is the average distance from sun to earth. Hence, if all celestial objects, located along the path of light from a galaxy would create, per a.u. distance, a billionth of the gravitational distortion, created by sun on our a.u. distance, then this would already be sufficient to consider the HHR as due to EGR.(M.Simhony, The Epola Space, 1990, 160 pp, and The Story of Matter and Space, 1999, 70 pp (available from the author). M.Simhony, Invitation to the Natural Physics of Matter, Space, and Radiation, World Scientific, 1994 (292 pp). See the website: http://come.to/natural_physics)

[JF.21] Possible Physical Causes of the Fivefold Variability of the Hubble Constant.

The Hubble constant varies from ~30 to ~150 km/s per megaparsec distance, depending on the "kind" of galaxy, the direction to it, etc. factors, unexplainable by the "expanding universe" model. The non-constancy of the Hubble constant also troubles this model, that requires the expansion rate of the universe at any given distance to be the same in all directions. But the original 1929 physical Hubble-Humason Law states that galaxial redshifts (HHR) are proportional to distance. This strengthens our presentation of HHR as Einstein's Gravitational Redshifts (EGR): they increase with distance, because the number of gravitationally distorted regions of space increases with the distance crossed by light. EGR values depend also on the direction to a galaxy, because the concentrations of distorted regions depend on this direction. Absorptional Redshifts (M.Simhony, The Epola Space, 1990, 160 pp, and The Story of Matter and Space, 1999, 70 pp (available from the author). M.Simhony, Invitation to the Natural Physics of Matter, Space, and Radiation, World Scientific, 1994 (292 pp). See the website: http://come.to/natural_physics) (due, e.g., to absorption followed by re-emission of lower energy quanta) behave similarly. The temperatures, stability, etc., of atoms and atomic matter in a galaxy may affect the Hubble constant due to Orbit Adjustment Redshifts and Blueshifts. ^1 With no physical reason for an "everything runaway from us", some galaxies may move toward us, causing blueshifts and so contributing to the variability of the Hubble constant.

[JF.22] Use of a gradient programmer to study the polyelectrolyte effect in xanthan

We present the results of a viscometric study of the polyelectrolyte effect in xanthan, a stiff polyelectrolyte, dissolved in water with a no added salt. These results are obtained by a novel method (Reed, W. F.,private commmunication) incorporating a gradient programmer to vary the concentration. This greatly speeds the acquisition of data as a function of concentration, but also complicates the analysis of data. Issues such as dead volume between detectors and high shear in capillary viscometery will be discussed, and their effect on the interpretation of viscometry data will be addressed.

[JF.23] Teaching Density Functional Theory Via the System of N Coupled Harmonic Oscillators

We present an elementary introduction to the density functional theory from the perspective of an exactly solvable quantum N-body system. The basic density functional is constructed from the exact wave function.

Part J of program listing