Physical Sciences and Mathematics Commons^™

Quantitative Method For Measurement Of The Goos-Hanchen Effect Based On Source Divergence Considerations, Jeffrey F. Gray, Ashok Puri

Physics Faculty Publications

In this paper we report on a method for quantitative measurement and characterization of the Goos-Hanchen effect based upon the real world performance of optical sources. A numerical model of a nonideal plane wave is developed in terms of uniform divergence properties. This model is applied to the Goos-Hanchen shift equations to determine beam shift displacement characteristics, which provides quantitative estimates of finite shifts near critical angle. As a potential technique for carrying out a meaningful comparison with experiments, a classical method of edge detection is discussed. To this end a line spread Green’s function is defined which can be …

Microwave Absorption Of Patterned Arrays Of Nanosized Magnetic Stripes With Different Aspect Ratios, Leszek M. Malkinski, Minghui Yu, Andriy Y. Voyk, Donald J. Scherer Ii, Leonard Spinu, Weillie Zhou, Scott Whittenburg, Zachary Davis, Jin-Seung Jung

Physics Faculty Publications

Arrays consisting of nanosized stripes of Permalloy with different length-to-width ratios have been fabricated using electron beam nanolithography, magnetron sputtering, and lift-off process. These stripes have a thickness of 100 nm, a width of 300 nm, and different lengths ranging from 300 nm to 100 μm. The stripes are separated by a distance of 1 μm. Magnetization hysteresis loops were measured using a superconducting quantum interference device susceptometer. Microwave absorption at 9.8 GHz was determined by means of ferromagnetic resonance technique. The dependence of the resonant field on the angle between the nanostructure and the in-plane dc magnetic …

Enhanced Spin-Dependent Tunneling Magnetoresistance In Magnetite Films Coated By Polystyrene, Wendong Wang, Leszek Malkinski, Jinke Tang

Physics Faculty Publications

Hematite films were deposited by magnetron sputtering. A phase transformation from hematite to magnetite occurred when polystyrene (PS) coated hematite films were annealed above 200 °C in hydrogen flow. Giant negative magnetoresistance (MR) was observed with the best MR ratio of over 8% (at room temperature and in a field of 5.5 T) found in samples annealed at 230 °C. The temperature dependence of the resistivity is characteristic of intergranular tunneling. After the PS layer was removed and the films annealed again at 230 °C in hydrogen flow, the resistivity increased by about one order of magnitude and the MR …

Size Dependence Of Static And Dynamic Magnetic Properties In Nanoscale Square Permalloy Antidot Arrays, Minghui Yu, Leszek Malkinski, Leonard Spinu, Weillie Zhou, Scott Whittenburg

Physics Faculty Publications

Permalloy antidot arrays with different square hole sizes (1200×1200, 800×800, and 400×400 nm²) have been fabricated by means of electron-beam lithography and lift-off techniques. The smaller square hole size results in enhanced remanence and reduced coercivity in the antidot array. Multiple resonance modes were clearly observed for the magnetic field applied normal to the array plane, and double uniform resonance modes occurred when the field deviated more than 30° from the normal to the plane. Two distinct dipolar field patterns with different orientations and magnitudes split the uniform resonance into double resonance modes. The double resonance modes show …

Dynamic And Temperature Effects In Toggle Magnetic Random Access Memory, Dorin Cimpoesu, Alexandru Stancu, Leonard Spinu

Physics Faculty Publications

In this paper we have studied the dynamic switching in magnetic random access memory (MRAM) and its dependence on thermal effects due to a finite temperature. The model is based on the Landau-Lifshitz-Gilbert equation and the stochastic Landau-Lifshitz-Gilbert equation which are numerically integrated. The magnetic layers are assumed to be ellipsoid shaped with each magnetic layer single domain. In addition, we have taken into account the uniaxial intrinsic anisotropy. Simulations were performed for both balanced and nonbalanced synthetic antiferromagnetic elements. The switching properties are discussed as a function of applied field pulses’ length and shape. In this paper we present …

Physics Of Complex Transverse Susceptibility Of Magnetic Particulate Systems, Dorin Cimpoesu, Alexandru Stancu, Leonard Spinu

Physics Faculty Publications

Complex transverse susceptibility is a recent proposed method for the determination of anisotropy and volume distributions in particulate magnetic media. So far, only thermal fluctuations and rate-dependent damped dynamics of the magnetic moment have been identified as reasons for the existence of the imaginary transverse susceptibility. In this paper, we apply a more general approach to derive the complex transverse susceptibility, and we show that the hysteresis phenomenon is the most general concept behind the existence of complex transverse susceptibility. In this paper, the physical origins of the imaginary part of transverse susceptibility are analyzed: rate-independent hysteresis, viscous-type rate-dependent hysteresis, …

An Evaluation Of Supercritical Drying And Peg/Freeze Drying Of Waterlogged Archaeological Wood, Eric Schindelholz, Robert Blanchette, Desmond C. Cook, Michael Drews, Steve Hand, Benjamin Held, Joel Jurgens, Betty Seifert

Physics Faculty Publications

This study was undertaken to evaluate the physical effects of drying waterlogged archaeological wood using supercritical carbon dioxide as compared to air drying and the popular polyethylene glycol (PEG)/freeze drying method. Previous studies have shown supercritical drying to be a potentially advantageous alternative to current methods of drying waterlogged wood through reduced processing time, minimal shrinkage, and increased success for reversibility. Samples in the form of blocks and planks of a few centimeters in size were prepared from two archaeological waterlogged wood sources and grouped into three treatment sets: one for air drying, one for PEG/freeze drying, and the other …

Lifecycle Analysis Of Cumulus Clouds Using A 3d Virtual Reality Environment, Thijs Heus, Harm J.J. Jonker, Eric J. Griffith, Frits H. Post

Physics Faculty Publications

No abstract provided.

The Influence Of The Sub-Cloud Moisture Field On Cloud Size Distributions And The Consequences For Entrainment, Harm J.J. Jonker, Remco A. Verzijlbergh, Thijs Heus, A. Pier Siebesma

Physics Faculty Publications

No abstract provided.

Why Do Descending Shells Around Cumulus Clouds Exist?, Thijs Heus, Harm J.J. Jonker

Physics Faculty Publications

No abstract provided.

Scaling Tests Of The Cross Section For Deeply Virtual Compton Scattering, C. Muñpz Camacho, A. Camsonne, M. Mazouz, C. Ferdi, G. Gavalian, E. Kuchina, M. Amaryan, K. A. Aniol, M. Beaumel, H. Benaoum, D. Hayes, C. E. Hyde-Wright, H. Ibrahim, P. E. Ulmer, L. B. Weinstein

Physics Faculty Publications

We present the first measurements of the ep → epγ cross section in the deeply virtual Compton scattering (DVCS) regime and the valence quark region. The Q² dependence (from 1.5 to 2.3 GeV²) of the helicity-dependent cross section indicates the twist-2 dominance of DVCS, proving that generalized parton distributions (GPDs) are accessible to experiment at moderate Q². The helicity-independent cross section is also measured at Q²=2.3 GeV². We present the first model-independent measurement of linear combinations of GPDs and GPD integrals up to the twist-3 approximation.

Phase Contrast Imaging Using Photothermally Induced Phase Transitions In Liquid Crystals, Chandra S. Yelleswarapu, Sri-Rajasekhar Kothapalli, Francisco J. Aranda, D.V.G.L.N. Rao, Yvonne Vaillancourt, Brian R. Kimball

Physics Faculty Publications

Phase contrast imaging is performed for live biological species using photothermal induced birefringence in dye doped liquid crystals. Using typical 4-f configuration, when liquid crystal cell is at back focal plane of Fourier lens, low spatial frequencies at center of Fourier spectrum are intense enough to induce local liquid crystal molecules into isotropic phase, whereas high spatial frequencies on the edges are not intense enough and remain in anisotropic phase. This results in π/2 phase difference between high and low spatial frequencies. This simple, inexpensive, all-optical, user-friendly, self-adaptive phase contrast imaging technique using low-power laser offers several distinct advantages.

Partial-Wave Expansions Of Angular Spectra Of Plane Waves, James A. Lock

Physics Faculty Publications

Focused electromagnetic beams are frequently modeled by either an angular spectrum of plane waves or a partial-wave sum of spherical multipole waves. The connection between these two beam models is explored here. The partial-wave expansion of an angular spectrum containing evanescent components is found to possess only odd partial waves. On the other hand, the partial-wave expansion of an alternate angular spectrum constructed so as to be free of evanescent components contains all partial waves but describes a propagating beam with a small amount of standing-wave component mixed in. A procedure is described for minimizing the standing-wave component so as …

Magnetopolaron Effect On Shallow Donors In Gan, A. Wysmolek, R. Stepniewski, M. Potemski, B. Chwalisz-Pietka, K. Pakula, J. M. Baranowski, David C. Look, S. S. Park, S. K. Lee

Physics Faculty Publications

Resonant interaction between longitudinal-optic (LO) phonons and electrons bound on shallow donors in GaN is studied using magnetoluminescence of neutral-donor bound excitons (D⁰X). The experiments were performed on high-quality freestanding GaN material and heteroepitaxial GaN layers grown on sapphire. In addition to the principal recombination channel of D⁰X, in which donors are left in their ground states, two-electron satellites (TES) involving different excited donor excitations, as well as replicas of the principal D⁰X transition due to LO phonons, were observed for the oxygen and silicon donors. In order to separate transitions involving ground and …

Quantifying Fluid Mixing With The Shannon Entropy, Marco Camesasca, Miron Kaufman, Ica Manas Zloczower

Physics Faculty Publications

We introduce a methodology to quantify the quality of mixing in various systems, including polymeric ones, by adapting the Shannon information entropy. For illustrative purposes we use particle advection of two species in a two-dimensional cavity flow. We compute the entropy by using the probability of finding a suitable chosen group/complex of particles of a given species, at a given location. By choosing the size of the group to be in direct proportion to the overall concentration of the components in the mixture we ensure that the entropic measure is maximized for the case of perfect mixing, that is, when …

Morphology Of The Near-Terminator Martian Ionosphere: A Comparison Of Models And Data, Jane L. Fox, Katherine E. Yeager

Physics Faculty Publications

We have constructed low and high solar activity models of the Martian thermosphere/ionosphere for solar zenith angles from 60 to 90° in 5 degree increments. The solar fluxes that we have adopted are those from the Solar 2000 v2.22 models of Tobiska (2004), without enhancements of the soft X-ray fluxes. The background neutral density and temperature profiles are similar to those that we have recently presented (Fox, 2004). We compute the density profiles for 14 ions and nine neutral species. For all the models, we present altitude profiles of the photoionization rates, electron impact ionization rates, total ion production rates, …

Revisiting Anomalous B(E2;4+1→2+1)/B(E2;2+1→0+1) Values In 98Ru And 180Pt, E. Williams, C. Plettner, E. A. Mccutchan, H. Levine, N. V. Zamfir, R. Cakirli, R. F. Casten, H. Ai, C. W. Beausang, G. Gurdal, A. Heinz, J. Qian, D. A. Meyer, N. Pietralla, V. Werner

Physics Faculty Publications

Recently, a set of nine nonmagic nuclei with anomalous values of the B(E2) ratio B_4/2 ≡ B(E2; 4⁺₁ → 2⁺₁)/B(E2; 2⁺₁ → 0⁺₁) were identified. Such values are outside the range allowed by current collective models. In the present work, the B(E2; 4⁺₁ → 2⁺₁) values for two of these nuclei, ⁹⁸Ru and ¹⁸⁰Pt, were re-measured to determine if the current literature values for these nuclei are correct. ^{98 …}

Collectivity And Configuration Mixing In 186,188Pb And 194Po, T. Grahn, A. Dewald, O. Moller, R. Julin, C. W. Beausang, S. Christen, I. G. Darby, S. Eeckhaudt, P. T. Greenlees, A. Gorgen, K. Helariutta, J. Jolie, P. Jones, S. Juutinen, H. Kettunen, T. Kroll, R. Krucken, Y. Le Coz, M. Leino, A. P. Leppanen, P. Maierbeck, D. A. Meyer, B. Melon, P. Nieminen, M. Nyman, R. D. Page, J. Pakarinen, P. Petkov, P. Rahkila, B. Saha, M. Sandzelius, J. Saren, C. Scholey, J. Uusitalo

Physics Faculty Publications

Lifetimes of prolate intruder states in ¹⁸⁶Pb and oblate intruder states in ¹⁹⁴Po have been determined by employing, for the first time, the recoil-decay tagging technique in recoil distance Doppler-shift lifetime measurements. In addition, lifetime measurements of prolate states in ¹⁸⁸Pb up to the 8⁺state were carried out using the recoil-gating method. The B(E2) values have been deduced from which deformation parameters lβ₂l = 0.29(5) and lβ₂l = 0.17(3) for the prolate and the oblate bands, respectively, have been extracted. The results also shed new light on the …

Magnetic Moment Softening And Domain Wall Resistance In Ni Nanowires, J. D. Burton, Renat F. Sabirianov, Sitaram Jaswal, Evgeny Y. Tsymbal, Oleg N. Mryasov

Physics Faculty Publications

We perform ab initio calculations of the electronic structure and conductance of atomic-size Ni nanowires with domain walls only a few atomic lattice constants wide. We show that the hybridization between noncollinear spin states leads to a reduction of the magnetic moments in the domain wall resulting in the enhancement of the domain wall resistance. Experimental studies of the magnetic moment softening may be feasible with modern techniques such as scanning tunneling spectroscopy.

Radiative Recombination And Ultralong Exciton Photoluminescence Lifetime In Gan Freestanding Film Via Two-Photon Excitation, Yongchun Zhong, Kam Sing Wong, Weili Zhang, David C. Look

Physics Faculty Publications

We have measured the photoluminescence (PL) lifetime of a freestanding GaN film using one-photon and two-photon excitations to demonstrate the dramatic difference in exciton recombination dynamics at the surface and in the bulk. An ultralong exciton PL lifetime of 17.2 ns at 295 K is observed from a GaN freestanding film using two-photon excitation, whereas less than 100 ps lifetime is observed for one-photon excitation, suggesting that nonradiative processes from surface defects account for the short PL lifetime measured. A monotonic increase in two-photon excited PL lifetime with increasing temperature and the linear dependence of the exciton lifetime with emission …

The Features Of Drosophila Core Promoters Revealed By Statistical Analysis, Naum I. Gershenzon, Edward N. Trifonov, Ilya P. Ioshikhes

Physics Faculty Publications

Background: Experimental investigation of transcription is still a very labor- and time-consuming process. Only a few transcription initiation scenarios have been studied in detail. The mechanism of interaction between basal machinery and promoter, in particular core promoter elements, is not known for the majority of identified promoters. In this study, we reveal various transcription initiation mechanisms by statistical analysis of 3393 nonredundant Drosophila promoters.

Results: Using Drosophila-specific position-weight matrices, we identified promoters containing TATA box, Initiator, Downstream Promoter Element (DPE), and Motif Ten Element (MTE), as well as core elements discovered in Human (TFIIB Recognition Element (BRE) and Downstream …

Probing The Universe On Gigaparsec Scales With Remote Cosmic Microwave Background Quadrupole Measurements, Emory F. Bunn

Physics Faculty Publications

Scattering of cosmic microwave background (CMB) radiation in galaxy clusters induces a polarization signal proportional to the CMB quadrupole anisotropy at the cluster’s location and lookback time. A survey of such remote quadrupole measurements provides information about large-scale cosmological perturbations. This paper presents a formalism for calculating the correlation function of remote quadrupole measurements in spherical harmonic space. The number of independent modes probed by both single-redshift and volume-limited surveys is presented, along with the length scales probed by these modes. In a remote quadrupole survey sparsely covering a large area of sky, the largest-scale modes probe the same-length scales …

Scattering Of A Tightly Focused Beam By An Optically Trapped Particle, James A. Lock, Susan Y. Wrbanek, Kenneth E. Weiland

Physics Faculty Publications

Near-forward scattering of an optically trapped 5-mu m-radius polystyrene latex sphere by the trapping beam was examined both theoretically and experimentally. Since the trapping beam is tightly focused, the beam fields superpose and interfere with the scattered fields in the forward hemisphere. The observed light intensity consists of a series of concentric bright and dark fringes centered about the forward-scattering direction. Both the number of fringes and their contrast depend on the position of the trapping beam focal waist with respect to the sphere. The fringes are caused by diffraction that is due to the truncation of the tail of …

Group Iv Solid State Proposals For Quantum Computation, Petru S. Fodor, J. Levy

Physics Faculty Publications

The discovery of the quantum factorization algorithm more than a decade ago triggered intense interest in exploring possible physical realizations of quantum computers. Among the many solid state proposals, electron and nuclear spins in Si and group IV related materials have long coherence times and the capability of state preparation, gating and read-out using electric, magnetic and optical fields. Proposals involving silicon seek to take advantage of an existing mature technology and the implicit promise of scalability from solid state materials. Nevertheless, building such quantum systems depends in many cases on the development of fabrication techniques with nearly atomic precision. …

Deducing The 237U(N,F) Cross Section Using The Surrogate Ratio Method, J. T. Burke, L. A. Bernstein, J. Escher, L. Ahle, J. A. Church, F. S. Dietrich, K. Moody, E. B. Norman, L. Phair, P. Fallon, R. M. Clark, M. A. Deleplanque, M. Descovich, M. Cromaz, I. Y. Lee, A. O. Macchiavelli, M. A. Mcmahan, E. Rodriguez-Vieitez, F. S. Stephens, H. Ai, C. Plettner, C. W. Beausang, B. Crider

Physics Faculty Publications

We have deduced the cross section for ²³⁷U(n, f) over an equivalent neutron energy range from 0 to 20 MeV using the surrogate ratio method. A 55 MeV⁴He beam from the 88 inch cyclotron at Lawrence Berkeley National Laboratory was used to induce fission in the following reactions: ²³⁸U(α, α^f) and ²³⁶U(α, α^f). The ²³⁸U reaction was a surrogate for ²³⁷U(n, f), and the ²³⁶U reaction was used as a surrogate for ²³⁵U(n, f). Scattered α particles were detected in a fully depleted segmented silicon telescope array …

Direct Evidence Of Impurity Decoration Of Ga Vacancies In Gan From Positron Annihilation Spectroscopy, S. Hautakangas, I. Makkonen, V. Ranki, J. Puska, K. Saarinen, X. Xu, David C. Look

Physics Faculty Publications

Positron annihilation spectroscopy, supported by ab initio theory, has been applied to verify the decoration of Ga vacancies in GaN by oxygen and hydrogen. Our results indicate that the Doppler broadening measurement of electron momentum distribution is sensitive enough to distinguish even between N and O atoms neighboring the Ga vacancy. We identify isolated V_Ga in electron irradiated GaN and V_Ga-O_N complexes in highly O-doped high-purity GaN. Evidence of H decoration of Ga vacancies is obtained in epitaxial GaN grown by metalorganic chemical-vapor deposition.

Magnetic Ordering In Gd Monopnictides: Indirect Exchange Versus Superexchange Interaction, Chun-Gang Duan, Renat F. Sabirianov, Wai-Ning Mei, Peter Dowben, Sitaram Jaswal, Evgeny Y. Tsymbal

Physics Faculty Publications

The exchange interaction parameters of Gd monopnictides are deduced from fitting the total energies of different magnetic configurations to those computed within the Heisenberg model. The magnetic structures predicted by first-principles calculations as well as the Curie (Néel) temperatures obtained from Monte Carlo simulations are both in good agreement with experiments. A detailed analysis of the exchange parameters suggests that the Ruderman-Kittel-Kasuya-Yosida-type indirect exchange interactions and antiferromagnetic superexchange interactions coexist in these compounds. The magnetic order changes from ferromagnetic in GdN to antiferromagnetic in other Gd pnictides as a result of the increased ionic radius of a pnictide in the …

Fast Ground State Manipulation Of Neutral Atoms In Microscopic Optical Traps, D. D. Yavuz, P. B. Kulatunga, E. Urban, Todd A. Johnson, N. Proite, T. Henage, T. G. Walker, M. Saffman

Physics Faculty Publications

We demonstrate Rabi flopping at MHz rates between ground hyperfine states of neutral ⁸⁷Rb atoms that are trapped in two micron sized optical traps. Using tightly focused laser beams we demonstrate high fidelity, site specific Rabi rotations with cross talk on neighboring sites separated by 8  μm at the level of 10⁻³. Ramsey spectroscopy is used to measure a dephasing time of 870  μs, which is ≈5000  times longer than the time for a π/2 pulse.

First Investigation Of Excited States In The Odd-Proton Nucleus Fr209, D. A. Meyer, C. W. Beausang, J. J. Ressler, H. Ai, H. Amro, M. Babilon, R. F. Casten, C. R. Fitzpatrick, G. Gurdal, A. Heinz, E. A. Mccutchan, C. Plettner, J. Qian, N. J. Thomas, V. Werner, E. Williams, N. V. Zamfir, Jing-Ye Zhang

Physics Faculty Publications

Excited states in ²⁰⁹Fr were produced following the ¹⁷⁶Yb(³⁷Cl, 4n) reaction. An excitation function was measured with data taken at 173, 179, and 185 MeV. Recoiling fusion-evaporation products were separated using the SASSYER gas-filled spectrometer. HPGe clover detectors of the YRAST Ball array at the target position and at the focal plane were used to detect prompt and delayed gamma ray decays, providing the first spectroscopic information about prompt and delayed transitions in ²⁰⁹Fr. The decay from a proposedπ i_13/2 configuration isomer was observed in ²⁰⁹Fr, and its half-life was measured …

Breakdown Of K Selection In 178Hf, A. B. Hayes, D. Cline, C. Wu, J. Ai, H. Amro, C. W. Beausang, R. F. Casten, J. Gerl, A. A. Hecht, A. Heinz, R. O. Hughes, R.V. F. Janssens, C. J. Lister, A. O. Macchiavelli, D. A. Meyer, E. F. Moore, P. Napiorkowski, R. C. Pardo, Ch. Schlegel, D. Seweryniak, M. W. Simon, J. Srebrny, R. Teng, K. Vetter, H. J. Wollersheim

Physics Faculty Publications

Coulomb activation of the four quasiparticle K^π = 16^{+ 178}Hf isomer (t _1/2 = 31 y) has led to the measurement of a set of Eλ matrix elements coupling the isomer band to the ground band. The present data combined with earlier ¹⁷⁸Hf Coulomb excitation data have probed the K components in the wave functions and revealed the onset and saturation of K mixing in low-K bands, whereas the mixing is negligible in the high-K bands. The implications can be applied to other quadrupole-deformed nuclei.