Physics Commons^™

Coherence Properties Of An Atom Laser, Marek Trippenbach, Y. B. Bland, Mark Edwards, Marya Doery, P. S. Julienne, E. W. Hagley, L. Deng, M. Kozuma, K. Helmerson, S. L. Rolston, W. D. Phillips

Physics & Astronomy: Faculty Publications

We study the coherence properties of an atom laser, which operates by extracting atoms from a gaseous Bose-Einstein condensate via a two-photon Raman process, by analysing a recent experiment (Hagley et al1999 Phys. Rev. Lett.833112). We obtain good agreement with the experimental data by solving the time-dependent Gross-Pitaevskii equation in three dimensions both numerically and with a Thomas-Fermi model. The coherence is strongly affected by the space-dependent phase developed by the condensate when the trapping potential is turned off.

Intercomparison Of Retrospective Radon Detectors, R. William Field, Daniel J. Steck, Mary Ann Parkhurst, Judy A. Mahaffey, Michael C.R. Alavanja

Physics Faculty Publications

We performed both a laboratory and a field intercomparison of two novel glass-based retrospective radon detectors previously used in major radon case-control studies performed in Missouri and Iowa. The new detectors estimate retrospective residential radon exposure from the accumulation of a long-lived radon decay product, ²¹⁰Pb, in glass. The detectors use track registration material in direct contact with glass surfaces to measure the α-emission of a ²¹⁰Pb-decay product, ²¹⁰Po. The detector's track density generation rate (tracks per square centimeter per hour) is proportional to the surface α-activity. In the absence of other strong sources of α-emission in …

Intensity Dependence Of Plateau Structures In Laser-Assisted X-Ray–Atom Scattering Processes, Dejan B. Miloševic, Anthony F. Starace

Anthony F. Starace Publications

The dependence on laser intensity of recently discovered plateau structures in laser-assisted x-ray–atom scattering, both with and without a static electric field present, is analyzed. Using the “three-step” model and the strong-field approximation we demonstrate a connection between laser-assisted, x-ray–atom scattering and high-order harmonic generation: For high laser-field intensities without a static field present, both processes have plateaus whose energies extend to the cutoff value 3.17U_p, where U_p is the ponderomotive potential energy. For x-ray–atom scattering in the presence of a static electric field we show that at high laser-field intensities two plateaus appear: One is …

Light Backscatter Of Milk Products For Transition Sensing Using Optical Fibers, Frederick A. Payne, Czarena L. Crofcheck, Sue E. Nokes, Klat C. Kang

Biosystems and Agricultural Engineering Faculty Publications

Transition sensors are needed, particularly in the dairy industry, for detecting transitions in pipe flow systems from product-to-water or product-to-product (such as from chocolate to vanilla ice cream mix). Transition information is used to automatically sequence valves to minimize product waste. Optical fibers were used to measure light backscatter between 400 and 950 nm as a function of milk concentration in water and milkfat concentration in milk. The normalized response (100% for product and 0% for water) as a function of product concentration in water was approximately logarithmic for skim milk between 400 and 900 nm and approximately linear for …

Velocity Distributions Of C Atoms In Co+ Dissociative Recombination: Implications For Photochemical Escape Of C From Mars, Jane L. Fox, Aleksander Hać

Physics Faculty Publications

We have carried out Monte Carlo calculations to determine the velocity distributions of C atoms produced by dissociative recombination of CO⁺ using recent data for the branching ratios of various allowed channels and ion and electron temperatures appropriate to the Martian thermosphere. We find that the fractions of ¹²C atoms with velocities greater than the escape velocity are ∼ 0.66 and ∼ 0.62, and those for ¹³C are ∼ 0.47 and ∼ 0.48 at the plasma temperatures characteristic of the exobases at low and high solar activities, respectively. The ratio of the escape fractions of ¹³C …

Strain Splitting Of The Gamma(5) And Gamma(6) Free Excitons In Zno, D. C. Reynolds, David C. Look, B. Jogai, C. W. Litton, T. C. Collins, M T. Harris, M. J. Callahan, J. S. Bailey

Physics Faculty Publications

High-quality ZnO crystals have been grown by vapor-phase techniques and by the hydrothermal method. Depending on the surface preparation technique, some hydrothermally grown crystals contain strain. These strains result in energy shifts of the free excitons as well as relaxation of the selection rules. The Γ₆ unallowed exciton is observed in these samples without the application of a magnetic field. The Γ₆ exciton is also observed to split in a strain field, consistent with the Γ₉ symmetry for the top valence band in ZnO. The Γ₅ and Γ₆ excitons have been observed to split in …

Laser-Induced Stabilization Of Autoionizing States, Heider N. Ereifej, J. Greg Story

Physics Faculty Research & Creative Works

Stabilization of autoionizing states of barium by laser-induced, stimulated emission of light is demonstrated. Relative to purely flourescent stabilization, the data clearly show an enhancement of the stabilization process for laser pulses short compared to the flourescent lifetime of the autoionizing states. Shakeup spectra in which the principal quantum number of both electrons changes during the stimulated emission process are also clearly demonstrated.

Measurement Of B Quark Fragmentation Fractions In The Production Of Strange And Light B Mesons In Pp̅ Collisions At √S =1.8 Tev, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

A new technique to measure the ratio of b quark fragmentation fractions in pp̅ collisions is described. Using a 70-pb^-1 sample of low-mass dimuon trigger data recorded with the Collider Detector at Fermilab, we identify B mesons by observing the double semileptonic decays b→cμX with c→sμ X. By counting the numbers of K*(892) ⁰, K*(892) ¹, and Φ (1020) mesons produced in association with these muon pairs, we measure the ratio of strange to nonstrange B meson production to be f_s /( f_u+ i>f_d)=[21.0±3.6(stat) _{-3.0 …}

Low-Frequency Noise In N-Gan With High Electron Mobility, M. E. Levinshtein, S. L. Rumyantsev, David C. Look, Richard J. Molnar, M. A. Khan, G. Simin, V. Adivarahan, M. S. Shur

Physics Faculty Publications

We report on the results of measurements of low frequency noise in n-type gallium nitride (GaN) grown on sapphire with 300 K electron mobility of 790 cm²/V s. The noise spectra have the form of 1/f noise with a Hooge parameter α of approximately 5×10⁻². This value of α is two orders of magnitude smaller than that observed before in n-GaN. The obtained results show that the level of flicker noise in GaN, just like that in GaAs and Si, strongly depends on the structural perfection of the material (the amplitude of the …

Crossover Photonic Switching Network With Cmos/Seed Smart Pixel Device And 2d Optical Fiber Bundle Array, Fengguang Luo, Mingcui Cao, Qiaoyan Hu, Anjun Wan, Jun Xu, Cong Deng, Deming Liu

Electro-Optics and Photonics Faculty Publications

A 16 X 16 Crossover photonic switching network with hybrid integrated CMOS/SEED smart pixel device and 2D optical fiber bundle array I/O access device is reported in this paper. SEEd array devices ar used as light receivers and transmitters, while CMOS devices make efficient logical processing. 4 X 40 2D multilayer optical fiber bundle arrays are fabricated and are used as I/O access devices in the crossover photonic switching network. The center to center spacing between adjacent optical fibers in the same layer of the fiber array is 125micrometers , and the spacing between adjacent layers is 250micrometers . Displacing …

Electro-Optic Response Of Surface-Induced Nematic Order Above The Nematic-Isotropic Phase Transition Temperature, Jong-Hyun Kim, Rolfe G. Petschek, Charles Rosenblatt

Faculty Scholarship

The optical retardation of a liquid crystal above the nematic-isotropic phase transition temperature TNI and subjected to planar alignment conditions at the substrate was investigated in the presence of an electric field applied normal to the substrates. The response was found to exhibit "S"-shaped behavior with electric field, and was larger near TNI than well above TNI. The results were examined in the context of a model that permits both biaxiality and a field-induced tilt of the molecular director. The results suggest that the primary effect of the electric field is to induce biaxiality, and in consequence suppress the order …

Slow-Binding Inhibition Of The Aminopeptidase From Aeromonas Proteolytica By Peptide Thiols: Synthesis And Spectroscopic Characterization, Kristi M. Huntington, David L. Bienvenue, Yaoming Wei, Brian Bennett, Richard C. Holz, Dehua Pei

Physics Faculty Research and Publications

Peptide-derived thiols of the general structure N-mercaptoacyl-leucyl-p-nitroanilide (1a−c) were synthesized and found to be potent, slow-binding inhibitors of the aminopeptidase from Aeromonas proteolytica (AAP). The overall potencies (K_I*) of these inhibitors against AAP range from 2.5 to 57 nM exceeding that of the natural product bestatin and approaching that of amastatin. The corresponding alcohols (2a−b) are simple competitive inhibitors of much lower potencies (K_I = 23 and 360 μM). These data suggest that the free thiols are involved in the formation of the E·I …

Coordinate Realizations Of Deformed Lie Algebras With Three Generator, Ranabir Dutt, Asim Gangopadhyaya, C. Rasinariu, Uday P. Sukhatne

Physics: Faculty Publications and Other Works

Differential realizations in coordinate space for deformed Lie algebras with three generators are obtained using bosonic creation and annihilation operators satisfying Heisenberg commutation relations. The unified treatment presented here contains as special cases all previously given coordinate realizations of so(2,1), so(3), and their deformations. Applications to physical problems involving eigenvalue determination in nonrelativistic quantum mechanics are discussed.

Resonant Enhancement Of Relativistic Electron Fluxes During Geomagnetically Active Periods, I Roth, M Temerin, M K. Hudson

Dartmouth Scholarship

The strong increase in the ̄ux of relativistic electrons during the recovery phase of magnetic storms and during other active periods is investigated with the help of Hamiltonian formalism and simulations of test electrons which interact with whistler waves. The intensity of the whistler waves is enhanced signi®cantly due to injection of 10±100 keV electrons during the substorm. Electrons which drift in the gradient and curvature of the magnetic ®eld generate the rising tones of VLF whistler chorus. The seed population of relativ- istic electrons which bounce along the inhomogeneous magnetic ®eld, interacts resonantly with the whistler waves. Whistler wave …

Comment On "Ideal Capacitor Circuits And Energy Conservation" By K. Mita And M. Boufaida [Am. J. Phys. 67 (8), 737-739 (1999)], Asim Gangopadhyaya, Jeffrey Mallow

Physics: Faculty Publications and Other Works

No abstract provided.

Performance Of The Cleo Iii Lif-Tea Ring Imaging Cherenkov Detector In A High Energy Muon Beam, Raymond Mountain, Marina Artuso, R. Ayad, F. Azfar

Physics - All Scholarship

The CLEO III Ring Imaging Cherenkov detector uses LiF radiators to generate Cherenkov photons which are then detected by proportional wire chambers using a mixture of CH$_4$ and TEA gases. The first two photon detector modules which were constructed, were taken to Fermilab and tested in a beam dump that provided high momentum muons. We report on results using both plane and "sawtooth" shaped radiators. Specifically, we discuss the number of photoelectrons observed per ring and the angular resolution. The particle separation ability is shown to be sufficient for the physics of CLEO III.

Search For The Flavor-Changing Neutral Current Decays B+→ Μ+Μ-K+ And B0→ Μ+Μ-K*0, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We report on a search for the flavor-changing neutral current decays B⁺→ μ⁺μ^-K⁺ and i>B⁰→ μ⁺μ^-K^*0 using 88 pb^-1 of data from p̅p collisions at √s =1.8 TeV, collected with the Collider Detector at Fermilab. Finding no evidence for these decays, we set upper limits on the branching fractions Ɓ(B⁺→ μ⁺μ^-K⁺) < 5.2 X 10^-6 and Ɓ(B⁺→ μ⁺μ^-K^*0) -6 at the 90% confidence level.

Computational Study Of Molecular Hydrogen In Zeolite Na-A. I. Potential Energy Surfaces And Thermodynamic Separation Factors For Ortho And Para Hydrogen, Cherry-Rose K. Anderson , '95, D. F. Coker, J. Eckert, Amy Lisa Graves

Physics & Astronomy Faculty Works

We simulate H-2 adsorbed within zeolite Na-A. We use a block Lanczos procedure to generate the first several (9) rotational eigenstates of the molecule, which is modeled as a rigid, quantum rotor with an anisotropic polarizability and quadrupole moment. The rotor interacts with Na cations and O anions; interaction parameters are chosen semiempirically and the truncation of electrostatic fields is handled with a switching function. A Monte Carlo proceedure is used to sample a set of states based on the canonical distribution. Potential energy surfaces, favorable adsorbtion sites, and distributions of barriers to rotation are analyzed. Separation factors for ortho-parahydrogen …

Inflation And Preheating In Nonoscillatory Models, Gary Felder, Lev Kofman, Andrei Linde

Physics: Faculty Publications

We study inflationary models in which the effective potential of the inflaton field does not have a minimum, but rather gradually decreases at large φ. In such models the inflaton field does not oscillate after inflation, and its effective mass becomes vanishingly small, so the standard theory of reheating based on the decay of the oscillating inflaton field does not apply. For a long time the only mechanism of reheating in such non-oscillatory (NO) models was based on gravitational particle production in an expanding universe. This mechanism is very inefficient. We will show that it may lead to cosmological problems …

Search For A Technicolor ΩT Particle In Events With A Photon And A B-Quark Jet At Fermilab, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

If the technicolor ω_T particle exists, a likely decay mode is ω_T→ γπ_T , followed by π_T → bb̅, yielding the signature γbb̅. We have searched 85 pb^-1 of data collected by the CDF experiment at the Fermilab Tevatron for events with a photon and two jets, where one of the jets must contain a secondary vertex implying the presence of a b quark. We find no excess of events above standard model expectations. We express the result as an exclusion region in the M_ωT -M_{πT …}

Differential Photometry Of Suspected Cataclysmic Variables, N. Bennert, I. König, E. Manthey, H. Bleul, K. Fieger, M. Hess, A. Hovest, W. Hovest, T. Jürges, J. Kleimann, C. Kriegeskorte, E. Krusch, D. Münstermann, D. Reymann, K. Rösler, M. Nielbock, M. Pohlen, L. Schmidtobreick, C. Tappert, R. Vanscheidt

Physics

No abstract provided.

Chiral Lagrangian Treatment Of Pi Eta Scattering, Joseph Schechter, Deirdre Black, Amir H. Fariborz

Physics - All Scholarship

We study pi eta scattering in a model which starts from the tree diagrams of a non-linear chiral Lagrangian including appropriate resonances. Previously, models of this type were applied to pi pi and pi K scattering and were seen to require the existence of light scalar sigma(560) and kappa(900) mesons and to be consistent with the f0(980). The present calculation extends this to include the a0(980), thereby completing a possible nonet of light scalars, all ``seen'' in the same manner. We note that, at the initial level, the pi eta channel is considerably cleaner than the pi pi and pi …

Differential Projectile Energy Loss In Multiply Ionizing Collisions, M. Schulz, R. Moshammer, W. Schmitt, H. Kollmus, R. Mann, S. Hagmann, Ronald E. Olson, J. Ullrich

Physics Faculty Research & Creative Works

The momentum vectors of the recoil ion and up to three electrons were measured in coincidence with the projectiles which did not change charge state for 3.6 MeV amu-1 Au53+ → Ne collisions. New techniques were applied to obtain differential energy-loss spectra for multiple-target ionization as a function of the recoil-ion charge state. A resolution unprecedented for this energy regime was achieved. The data are in good agreement with a classical trajectory Monte Carlo calculation. Our studies represent a first step for a method of modelling stopping powers on a microscopic level and are relevant for plasma applications.

State-To-State Rotational Excitation Of Co By H2 Near 1000 Cm-1 Collision Energy, Stiliana Antonova, Antonis P. Tsakotellis, Ao Lin, George C. Mcbane

Peer Reviewed Articles

Relative state-to-state rotationally inelastic cross sections for excitation of carbon monoxide by hydrogen were measured in a crossed molecular beam experiment at collision energies 795, 860, and 991 cm^-1. The results are compared to predictions of a recent ab initio potential energy surface [J. Chem. Phys. 108, 3554 (1998)]. The agreement is very good. A comparison with older data on thermally averaged total depopulation cross sections [Chem. Phys. 53, 165 (1980)] indicates that the absolute magnitudes of the cross sections predicted by the surface are too high. The CO excitation is dominated by collisions that are …

Phonon And Elastic Instabilities In Moc And Mon, Gus L. W. Hart, Barry M. Klein

Faculty Publications

We present several results related to the instability of MoC and MoN in the B1 (sodium chloride) structure. These compounds were proposed as potential superconductors with moderately high transition temperatures. We show that the elastic instability in B1-structure MoN, demonstrated several years ago, persists at elevated pressures, thus offering little hope of stabilizing this material without chemical doping. For MoC, another material for which stoichiometric fabrication in the B1 structure has not proven possible, we find that all of the cubic elastic constants are positive, indicating elastic stability. Instead, we find X-point phonon instabilities in MoC (and in MoN as …

Multiphoton Ionization Of V, Cr, Y, La, And Ir Through 0.5-Ps Ultraviolet Laser Pulses, B. Witzel, N. A. Poppadogiannis, Cornelis J. Uiterwaal, H. Schröder, D. Charalambidis

C.J.G.J. Uiterwaal Publications

The two-photon ionization of the metal atoms V, Cr, Y, La, and Ir sputtered by an Ar-ion gun from solid targets has been investigated using linearly polarized laser pulses of 500- fs duration and 248.6-nm (KrF) wavelength in combination with mass spectroscopy that is free of volume effects. A near-resonant ionization process has to be attributed to all five atoms. By fitting analytical solutions of a rate equation model describing the temporal evolution of the ionization process, we can determine absolute values of the one-photon cross sections and saturation intensities.

High-Order Harmonic Generation In Magnetic And Parallel Magnetic And Electric Fields, Dejan B. Miloševic, Anthony F. Starace

Anthony F. Starace Publications

We demonstrate control of high-harmonic generation (HHG) by a linearly polarized laser field using uniform static magnetic and electric fields parallel to the laser polarization. We show that the harmonic intensity can be considerably increased for particular values of the magnetic field. The maximum values of the harmonic intensity correspond to such values of magnetic induction for which an integer multiple of the classical cyclotron period of the electron’s motion perpendicular to the magnetic field is equal to the return time of the ionized electron wave packet to the nucleus under the influence of the laser field (and static electric …

A Simplified Gaas Polarized Electron Source, H. M. Al-Khateeb, B. G. Birdsey, T. C. Bowen, A. S. Green, M. E. Johnston, Timothy J. Gay

Timothy J. Gay Publications

We report operational and construction details of a simplified GaAs polarized electron source. It is contained in a modified 4.63 in. Conflat four-way cross, and uses a single 56 ℓ /s turbomolecular pump. The design incorporates multiple cesiators to extend source lifetime, a new spring-clamp GaAs crystal mounting design to provide uniform crystal heating, and a very simple tubular 90° electrostatic deflector. We also discuss matters related to preparing, heat cleaning, and activating the GaAs crystal.

Parity Nonconservation In 106pd And 108pd Neutron Resonances, Bret E. Crawford, J D. Bowman, P P J. Delheij, T Haseyama, J N. Knudsen, L Y. Lowie, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, H Postma, N R. Roberson, S J. Seestrom, E I. Sharapov, Sharon L. Stephenson, V W. Yuan

Physics and Astronomy Faculty Publications

Parity nonconservation (PNC) has been studied in the neutron p-wave resonances of ¹⁰⁶Pd and ¹⁰⁸Pd in the energy range of 20 to 2000 eV. Longitudinal asymmetries in p-wave capture cross sections are measured using longitudinally polarized neutrons incident on ∼20-g metal-powder targets at LANSCE. A CsI γ-ray detector array measures capture cross section asymmetries as a function of neutron energy which is determined by the neutron time-of-flight method. A total of 21 p-wave resonances in ¹⁰⁶Pd and 21 p-wave resonances in ¹⁰⁸Pd were studied. One statistically significant PNC effect was observed in¹⁰⁶Pd, and no …

The Microchannel Flow Of A Micropolar Fluid, Guohua Liu

Doctoral Dissertations

Micro-channel flows have been computed to investigate the influence of Navier-Stokes formulation for the slip-flow boundary condition, and a micro-polar fluid model, respectively.

The results of the slip boundary condition show that the current methodology is valid for slip-flow regime (i.e., for values of Knudsen number less than approximately 0.1). Drag reduction phenomena apparent in some micro-channels can be explained by slip-flow theory. These results are in agreement with some computations and experiments.

An ad hoc micro-polar fluid model is developed to investigate the influence of micro effects, such as micro-gyration, in micro-scale flows. The foundation of the ad hoc …