Physics Commons^™

(207)Pb Spin-Lattice Relaxation In Solid Pbmoo(4) And Pbcl(2), Peter A. Beckmann, Shi Bai, Alexander J. Vega, Cecil Dybowski

Physics Faculty Research and Scholarship

We have measured the (207)Pb nuclear spin-lattice relaxation rate R as a function of temperature T at two nuclear magnetic resonance frequencies omega(0) in the ionic solids lead molybdate (PbMoO(4)) and lead chloride (PbCl(2)). R is unexpectedly large, proportional to T(2), and independent of omega(0). Taken together with previous work in lead nitrate [Pb(NO(3))(2)], these results show that the relaxation does not depend on the nature or rotational motion of the counterion, particularly since the counterion in lead chloride is a single chlorine atom. The theory that explains the observed relaxation rate is reviewed. A second-order Raman process dominates the …

Two-Loop Bethe Logarithms For Non- S Levels, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

Two-loop Bethe logarithms are calculated for excited P and D states in hydrogenlike systems, and estimates are presented for all states with higher angular momenta. These results complete our knowledge of the P and D energy levels in hydrogen at the order of α⁸ m_ec², where me is the electron mass and c is the speed of light, and scale as Z⁶, where Z is the nuclear charge number. Our analytic and numerical calculations are consistent with the complete absence of logarithmic terms of order (απ)² (Zα)⁶ ln [(Zα)^-2] …

Differential Electron Emission For Single And Multiple Ionization Of Argon By 500 Ev Positrons, Jared M. Gavin, Robert D. Dubois, O. G. De Lucio

Physics Faculty Research & Creative Works

Triply differential electron emission cross sections are measured for single ionization of argon by 500 eV positrons. Data are presented for coincidences between projectiles scattered into angles of 3° and electrons with emission energies less than 10 eV that are observed between 45 and 135° along the beam direction. For interpretation, these are compared to cosine squared representations of the binary and recoil lobes which are convoluted over experimental parameters. Singly differential electron emission data for double and triple ionization by positrons are also presented.

A Handheld Neutron-Detection Sensor System Utilizing A New Class Of Boron Carbide Diode, Kevin Osberg, Nathan Schemm, M. Susan Hallbeck, Sina Balkir, Peter A. Dowben, Jennifer I. Brand, Michael W. Hoffman

Peter Dowben Publications

A handheld neutron-detection sensor application is described in this paper. The sensor system utilizes a new class of boron carbide diode that interacts with incoming neutrons. To interface with the boron carbide diode, an integrated front end is designed in a 1.5-μm standard CMOS technology. With the diode and front-end microchip, a handheld neutron-detection system was realized with an embedded microcontroller for real-time processing. The handheld detector operation was then tested with a plutonium–beryllium neutron source. Test and measurement results confirm the validity of the approach and the functionality of the design.

Theory Of Cavity-Polariton Self-Trapping And Optical Strain In Polymer Chains, M. V. Katkov, Yuriy V. Pershin Dr, C. Piermarocchi

Faculty Publications

We consider a semiconductor polymer chain coupled to a single electromagnetic mode in a cavity. The excitations of the chain have a mixed exciton-photon character and are described as polaritons. Polaritons are coupled to the lattice by the deformation potential interaction and can propagate in the chain. We find that the presence of optical excitation in the polymer induces strain on the lattice. We use a BCS variational wave function to calculate the chemical potential of the polaritons as a function of their density. We analyze first the case of a short chain with only two unit cells in order …

Single Top Quark Production At The Fermilab Tevatron: Threshold Resummation And Finite-Order Soft Gluon Corrections, Nikolaos Kidonakis

Faculty Articles

I present a calculation of threshold soft-gluon corrections to single top-quark production in p(p) collisions via all partonic processes in the t and s channels and via associated top quark and W boson production. The soft-gluon corrections are formally resummed to all orders, and finite-order expansions of the resummed cross section are calculated through next-to-next-to-next-to-leading-order (NNNLO) at next-to-leading logarithmic (NLL) accuracy. Numerical results for single top-quark production at the Tevatron are presented, including the dependence of the cross sections on the top-quark mass and on the factorization and renormalization scales. The threshold corrections in the t channel are small while …

New Cuoricino Results And Status Of Cuore, O. Cremonesi, R. Ardito, C. Arnaboldi, D.R. Artusa, F.T. Avignone Iii, M. Balata, I. Bandac, M. Barucci, J.W. Beeman, F. Bellini, C. Brofferio, C. Bucci, S. Capelli, F. Capozzi, L. Carbone, S. Cebrian, M. Clemenza, C. Cosmelli, R.J. Creswick, I. Dafinei, A. De Waard, M. Dolinski, H.A. Farach, F. Ferroni, C. Gargiulo, E. Guardincerri, A. Giuliani, P. Gorla, Thomas D. Gutierrez, E.E. Haller, I.G. Irastorza, E. Longo, G. Maier, R. Maruyama, S. Morganti, S. Nisi, C. Nones, E.B. Norman, A. Nucciotti, E. Olivieri, P. Ottonello, M. Pallavicini, E. Palmieri, M. Pavan, M. Pedretti, G. Pessina, S. Pirro, E. Previtali, B. Quiter, L. Risegari, C. Rosenfeld, S. Sangiorgio, M. Sisti, A.R. Smith, L. Torres, G. Ventura, N. Xu, L. Zanotti

Physics

CUORICINO is an array of 62 TeO₂ bolometers with a total mass of 40.7 kg (11.2 kg of ¹³⁰Te), operated at about 10 mK to search for ββ(0ν) of ¹³⁰Te. The detectors are organized as a 14-story tower and intended as a slightly modified version of one of the 19 towers of the CUORE project, a proposed tightly packed array of 988 TeO₂ bolometers (741 kg of total mass of TeO₂) for ultralow-background searches on neutrinoless double-beta decay, cold dark matter, solar axions, and rare nuclear decays. Started in April 2003 at …

Computationally Modeling The Effects Of Surface Roughness On Soft X-Ray Multilayer Reflectors, Jedediah Edward Jensen Johnson

Theses and Dissertations

Electromagnetic scattering from a rough two dimensional homogeneous scatterer has been computationally modeled. The scatterer is intended to simulate reflection from a two interface multilayer. The rough scatterer was created from Gaussian random points centered about an ideal interface. The points were connected with a third order spline interpolant which accounts for correlation between neighboring surface atoms. The scalar electric field integral equation (EFIE) and magnetic field integral equation (MFIE) were solved using the Nystrom method to obtain the reflected intensity as a function of observation angle. Verification of the accuracy of the code was obtained by means of comparison …

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.

Holographic Patterning Of Polymer Dispersed Liquid Crystal Materials For Diffractive Optical Elements, Robert Allan Ramsey

Physics Dissertations - Archive

Liquid crystals are a soft condensed matter phase that share properties with both isotropic liquids and crystalline solids. Composite materials formed from both low molecular weight liquid crystals and polymers are of both fundamental and technological importance. One method for preparing dispersions of polymers and liquid crystals is polymerization-induced phase separation. Photo-polymerization induced phase separation utilizes a mixture of a liquid crystal and a photo curable polymer contained between two indium tin-oxide (ITO) coated glass substrates. Irradiation of the homogeneous pre-polymer mixture initiates polymerization, which in turn induces a phase separation between the polymer and liquid crystal. Holographically patterned polymer …

Near-Field Thermal Radiative Transfer And Thermoacoustic Effects From Vapor Plumes Produced By Pulsed Co/Sub 2 /Laser Ablation Of Bulk Water, S. I. Kudryashov, Kevin Lyon, S. D. Allen

Mechanical Engineering - Daytona Beach

Submillimeter deep heating of bulk water by thermal radiation from ablative water plumes produced by a 10.6 μm transversely excited atmospheric C O2 laser and the related acoustic generation has been studied using a contact time-resolved photoacoustic technique. Effective penetration depths of thermal radiation in water were measured as a function of incident laser fluence and the corresponding plume temperatures were estimated. The near-field thermal and thermoacoustic effects of thermal radiation in laser-ablated bulk water and their potential near-field implications are discussed.

c 2006 American Institute of Physics

Cuore: An Experiment To Investigate For Neutrinoless Double Beta Decay By Cooling 750 Kg Of Teo2 Crystals At 10 Mk, J. Beeman, M. Dolinski, T.D. Gutierrez, E.E. Haller, R. Maruyama, A.R. Smith, N. Xu, A. Giuliani, M. Pedretti, S. Sangiorgio, M. Barucci, E. Olivieri, L. Risegari, G. Ventura, M Balata, C. Bucci, S. Nisi, E. Palmieri, A. De Waard, E.B. Norman, C. Arnaboldi, C. Brofferio, S. Capelli, F. Capozzi, L. Carbone, M. Clemenza, O Cremonesi, E. Fiorini, C Nones, A. Nucciotti, M. Pavan, G Pessina, S Pirro, E Previtali, M. Sisti, L Torres, L Zanotti, R. Ardito, G. Maier, E. Guardincerri, P Ottonello, M Pallavicini, D.R. Artusa, F. T. Avignone Iii, I. Bandac, R.J. Creswick, H.A. Farach, C. Rosenfeld, S Cebrian, P. Gorla, Ig Irastorza, F Bellini, C Cosmelli, I Dafinei, M Diemoz, F Ferroni, C Gargiulo, E Longo, S Morganti

Physics

CUORE (Cryogenic Underground Observatory for Rare Events) is an experiment proposed to infer the effective Majorana mass of the electron neutrino from measurements on neutrinoless double beta decay (0νDBD). The goal of CUORE is to achieve a background rate in the range 0.001 to 0.01 counts/keV/kg/y at the 0νDBD transition energy of ¹³⁰Te (2528 keV). The proposed experiment, to be mounted in the underground Gran Sasso INFN National Laboratory, Italy, is realized by cooling about 1000 TeO₂ bolometers, of 750 g each, at a temperature of 10mK. We will describe the experiment, to be cooled by an extremely …

The All Boron Carbide Diode Neutron Detector: Comparison With Theory, A. N. Caruso, Peter A. Dowben, S. Balkir, Nathan Schemm, Kevin Osberg, R.W. Fairchild, Oscar Barrios Flores, Snjezana Balaz, A.D. Harken, Brian W. Robertson, Jennifer I. Brand

Peter Dowben Publications

A boron carbide diode detector, fabricated from two different polytypes of semiconducting boron carbide, will detect neutrons in reasonable agreement with theory. Small deviations from the model calculations occur due to the detection efficiencies of the ¹⁰B capture products Li plus α sum signal differing somewhat from expectation in the thin diodes. The performance of the all boron carbide neutron detector does depart from the behavior of devices where a boron rich neutron capture layer is distinct from the diode charge collection region (i.e. a conversion layer solid state detector), as is expected.

Fluorescence Blinking Statistics From Cdse Core And Core/Shell Nanorods, S. Wang, C. Querner, Thomas B. Emmons , '08, M. Drndic, Catherine Hirshfeld Crouch

Physics & Astronomy Faculty Works

We report fluorescence blinking statistics measured from single CdSe nanorods (NRs) of seven different sizes with aspect ratios ranging from 3 to 11. This study also included core/shell CdSe/ZnSe NRs and core NRs with two different surface ligands producing different degrees of surface passivation. We compare the findings for NRs to our measurements of blinking statistics from spherical CdSe core and CdSe/ZnS core/shell nanocrystals (NCs). We find that, for both NRs and spherical NCs, the off-time probability distributions are well described by a power law, while the on-time probability distributions are best described by a truncated power law, P(tau(on)) similar …

Structured Waves Near The Plasma Frequency Observed In Three Auroral Rocket Flights, M Samara, J Labelle

Dartmouth Scholarship

Abstract. We present observations of waves at and just above the plasma frequency (fpe) from three high frequency electric field experiments on three recent rockets launched to altitudes of 300–900 km in active aurora. The predominant observed HF waves just above fpe are narrowband, short- lived emissions with amplitudes ranging from <1mV/m to 20 mV/m, often associated with structured electron den- sity. The nature of these HF waves, as determined from frequency-time spectrograms, is highly variable: in some cases, the frequency decreases monotonically with time as in the “HF-chirps” previously reported (McAdams and La- Belle, 1999), but in other cases rising frequencies are ob- served, or features which alternately rise and fall in fre- quency. They exhibit two timescales of amplitude variation: a short timescale, typically 50–100 ms, associated with in- dividual discrete features, and a longer timescale associated with the general decrease in the amplitudes of the emissions as the rocket moves away from where the condition f ∼fpe holds. The latter timescale ranges from 0.6 to 6.0 s, corre- sponding to distances of 2–7 km, assuming the phenomenon to be stationary and using the rocket velocity to convert time to distance.

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.

Measurement Of The Top Quark Mass In The Lepton +Jets Final State With The Matrix Element Method, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Kenneth Bloom Publications

We present a measurement of the top quark mass with the matrix element method in the lepton +jets final state. As the energy scale for calorimeter jets represents the dominant source of systematic uncertainty, the matrix element likelihood is extended by an additional parameter, which is defined as a global multiplicative factor applied to the standard energy scale. The top quark mass is obtained from a fit that yields the combined statistical and systematic jet energy scale uncertainty. Using a data set of 0.4 fb^-1 taken with the D0 experiment at Run II of the Fermilab Tevatron Collider, the …

Precise Radial Velocities Of Giant Stars. Ii. Pollux And Its Planetary Companion, Sabine Reffert, Andreas Quirrenbach, David Mitchell, Simon Albrecht, Saskia Hekker, Debra A. Fischer, Geoffrey W. Marcy, R. Paul Butler

Physics

It has long been speculated that the observed periodic radial velocity pattern for the K giant Pollux might be explained in terms of an orbiting planetary companion. We have collected 80 high-resolution spectra for Pollux at Lick Observatory yielding precise radial velocities with a mean error of 3.8 m s^-1, providing the most comprehensive and precise data set available for this star. Our data confirm the periodicity previously seen in the radial velocities. We derive a period of 589.7 ± 3.5 days and, assuming a primary mass of 1.86 M, a minimum companion mass of 2.9 ± …

Are Domain Walls In Spin Glasses Described By Stochastic Loewner Evolutions?, Alan Middleton, Denis Bernard, Pierre Le Doussal

Physics - All Scholarship

Domain walls for spin glasses are believed to be scale invariant invariant; a stronger symmetry, conformal invariance, has the potential to hold. The statistics of zero-temperature Ising spin glass domain walls in two dimensions are used to test the hypothesis that these domain walls are described by a Schramm-Loewner evolution SLE$_\kappa$. Multiple tests are consistent with SLE$_\kappa$, where $\kappa=2.30(5)$. Both conformal invariance and the domain Markov property are tested. The latter does not hold in small systems, but detailed numerical evidence suggests that it holds in the continuum limit.

Neutral Kaon Interferometry In Au+Au Collisions At √SNn = 200 Gev, B.I. Abelev, M.M. Aggarwal, Z. Ahammed, J. Amonett, B.D. Anderson, M. Anderson, D. Arkhipkin, G.S. Averichev, Y. Bai, J. Balewski, O. Barannikova, L.S. Barnby, J. Baudot, S. Bekele, V.V. Belaga, A. Bellingeri-Laurikainen, R. Bellwied, F. Benedosso, S. Bhardwaj, A. Bhasin, A.K. Bhati, H. Bichsel, J. Bielcik, J. Bielcikova, L.C. Bland, S.-L. Blyth, B.E. Bonner, M. Botje, J. Bouchet, A.V. Brandin, A. Bravar, T.P. Burton, M. Bystersky, R.V. Cadman, X.Z. Cai, H. Caines, M. Calderón De La Barca Sánchez, J. Castillo, O. Catu, D. Cebra, Z. Chajecki, P. Chaloupka, S. Chattopadhyay, H.F. Chen, J.H. Chen, J. Cheng, M. Cherney, A. Chikanian, W. Christie, J.P. Coffin, T.M. Cormier, M.R. Cosentino, J.G. Cramer, H.J. Crawford, D. Das, S. Das, S. Dash, M. Daugherity, M.M. De Moura, T.G. Dedovich, M. Dephillips, A.A. Derevschikov, L. Didenko, T. Dietel, P. Djawotho, S.M. Dogra, W.J. Dong, X. Dong, J.E. Draper, F. Du, V.B. Dunin, J.C. Dunlop, M.R. Dutta Mazumdar, V. Eckardt, W.R. Edwards, L.G. Efimov, V. Emelianov, J. Engelage, G. Eppley, B. Erazmus, M. Estienne, P. Fachini, R. Fatemi, J. Fedorisin, K. Filimonov, P. Filip, E. Finch, V. Fine, Y. Fisyak, J. Fu, C.A. Gagliardi, L. Gaillard, M.S. Ganti, V. Ghazikhanian, P. Ghosh, J.E. Gonzalez, Y.G. Gorbunov, H. Gos, O. Grebenyuk, D. Grosnick, S.M. Guertin, K.S.F.F. Guimaraes, N. Gupta, T.D. Gutierrez, B. Haag, T.J. Hallman, A. Hamed, J.W. Harris, W. He, M. Heinz, T.W. Henry, S. Hepplemann, B. Hippolyte, A. Hirsch, E. Hjort, A.M. Hoffman, G.W. Hoffmann, M.J. Horner, H.Z. Huang, S.L. Huang, E.W. Hughes, T.J. Humanic, G. Igo, P. Jacobs, W.W. Jacobs, P. Jakl, F. Jia, H. Jiang, P.G. Jones, E.G. Judd, S. Kabana, K. Kang, J. Kapitan, M. Kaplan, D. Keane, A. Kechechyan, V.Yu. Khodyrev, B.C. Kim, J. Kiryluk, A. Kisiel, E.M. Kislov, S.R. Klein, A. Kocoloski, D.D. Koetke, T. Kollegger, M. Kopytine, L. Kotchenda, V. Kouchpil, K.L. Kowalik, M. Kramer, P. Kravtsov, V.I. Kravtsov, K. Krueger, C. Kuhn, A.I. Kulikov, A. Kumar, A.A. Kuznetsov, M.A.C. Lamont, J.M. Landgraf, S. Lange, S. Lapointe, F. Laue, J. Lauret, A. Lebedev, R. Lednicky, C.-H. Lee, S. Lehocka, M.J. Levine, C. Li, Q. Li, Y. Li, G. Lin, X. Lin, S.J. Lindenbaum, M.A. Lisa, F. Liu, H. Liu, J. Liu, L. Liu, Z. Liu, T. Ljubicic, W.J. Llope, H. Long, R.S. Longacre, W.A. Love, Y. Lu, T. Ludlam, D. Lynn, G.L. Ma, J.G. Ma, Y.G. Ma, D. Magestro, D.P. Mahapatra, R. Majka, L.K. Mangotra, R. Manweiler, S. Margetis, C. Markert, L. Martin, H.S. Matis, Yu.A. Matulenko, C.J. Mcclain, T.S. Mcshane, Yu. Melnick, A. Meschanin, J. Millane, M.L. Miller, N.G. Minaev, S. Mioduszewski, C. Mironov, A. Mischke, D.K. Mishra, J. Mitchell, B. Mohanty, L. Molnar, C.F. Moore, D.A. Morozov, M.G. Munhoz, B.K. Nandi, C. Nattrass, T.K. Nayak, J.M. Nelson, P.K. Netrakanti, L.V. Nogach, S.B. Nurushev, G. Odyniec, A. Ogawa, V. Okorokov, M. Oldenburg, D. Olson, M. Pachr, S.K. Pal, Y. Panebratsev, S.Y. Panitkin, A.I. Pavlinov, T. Pawlak, T. Peitzmann, V. Perevoztchikov, C. Perkins, W. Peryt, S.C. Phatak, R. Picha, M. Planinic, J. Pluta, N. Poljak, N. Porile, J. Porter, A.M. Poskanzer, M. Potekhin, E. Potrebenikova, B.V.K.S. Potukuchi, D. Prindle, C. Pruneau, J. Putschke, G. Rakness, R. Raniwala, S. Raniwala, R.L. Ray, S.V. Razin, J. Reinnarth, D. Relyea, F. Retiere, A. Ridiger, H.G. Ritter, J.B. Roberts, O.V. Rogachevskiy, J.L. Romero, A. Rose, C. Roy, L. Ruan, M.J. Russcher, R. Sahoo, T. Sakuma, S. Salur, J. Sandweiss, M. Sarsour, P.S. Sazhin, J. Schambach, R.P. Scharenberg, N. Schmitz, K. Schweda, J. Seger, I. Selyuzhenkov, P. Seyboth, A. Shabetai, E. Shahaliev, M. Shao, M. Sharma, W.Q. Shen, S.S. Shimanskiy, E. Sichtermann, F. Simon, R.N. Singaraju, N. Smirnov, R. Snellings, G. Sood, P. Sorensen, J. Sowinski, J. Speltz, H.M. Spinka, B. Srivastava, A. Stadnik, T.D.S. Stanislaus, R. Stock, A. Stolpovsky, M. Strikhanov, B. Stringfellow, A.A.P. Suaide, E. Sugarbaker, M. Sumbera, Z. Sun, B. Surrow, M. Swanger, T.J.M. Symons, A. Szanto De Toledo, A. Tai, J. Takahashi, A.H. Tang, T. Tarnowsky, D. Thein, J.H. Thomas, A.R. Timmins, S. Timoshenko, M. Tokarev, T.A. Trainor, S. Trentalange, R.E. Tribble, O.D. Tsai, J. Ulery, T. Ullrich, D.G. Underwood, G. Van Buren, N. Van Der Kolk, M. Van Leeuwen, A.M. Vander Molen, R. Varma, I.M. Vasilevski, A.N. Vasiliev, R. Vernet, S.E. Vigdor, Y.P. Viyogi, S. Vokal, S.A. Voloshin, W.T. Waggoner, F. Wang, G. Wang, J.S. Wang, X.L. Wang, Y. Wang, J.W. Watson, J.C. Webb, G.D. Westfall, A. Wetzler, C. A. Whitten Jr., H. Wieman, S.W. Wissink, R. Witt, J. Wood, J. Wu, N. Xu, Q.H. Xu, Z. Xu, P. Yepes, I-K. Yoo, V.I. Yurevich, W. Zhan, H. Zhang, W.M. Zhang, Y. Zhang, Z.P. Zhang, Y. Zhao, C. Zhong, R. Zoulkarneev, Y. Zoulkarneeva, A.N. Zubarev, J.X. Zuo

Physics

We present the first statistically meaningful results from two-K_s⁰ interferometry in heavy-ion collisions at √s_NN = 200 GeV. A model that takes the effect of the strong interaction into account has been used to fit the measured correlation function. The effects of single and coupled channels were explored. At the mean transverse mass ⟨m_T⟩ = 1.07 GeV, we obtain the values R = 4.09±0.46(stat)±0.31(sys) fm and λ=0.92±0.23(stat)±0.13(sys), where R and λ are the invariant radius and chaoticity parameters, respectively. The results are qualitatively consistent with m_T systematics established with pions in …

Domain Overlap In Antiferromagnetically Coupled [Co/Pt]/Nio/ [Co/Pt] Multilayers, Andrew Baruth, Lu Yuan, John D. Burton, Karolina Janicka, Evgeny Y. Tsymbal, Sy_Hwang Liou, Shireen Adenwalla

Sy-Hwang Liou Publications

Antiferromagnetically coupled magnetic thin films with perpendicular anisotropy exhibit domain overlap regions originating from magnetostatic stray fields localized in the vicinity of the domain walls. Using high resolution magnetic force microscopy, the authors investigate these overlap regions in [Co/Pt] /NiO/ [Co/Pt] multilayers with various strengths of the interlayer exchange coupling. They develop a simple model that provides a quantitative explanation of the formation of these regions and the relationship between the domain overlap width and the coupling strength. Their results are important for application of magnetic layered structures with perpendicular anisotropy in advanced magnetoresistive devices.

Graded Interface Models For More Accurate Determination Of Van Der Waals-London Dispersion Interactions Across Grain Boundaries, Roger H. French

Faculty Scholarship

Attractive van der Waals–London dispersion interactions between two half crystals arise from local physical property gradients within the interface layer separating the crystals. Hamaker coefficients and London dispersion energies were quantitatively determined for Σ5 and near-∑13 grain boundaries in SrTiO3 by analysis of spatially resolved valence electron energy-loss spectroscopy (VEELS) data. From the experimental data, local complex dielectric functions were determined, from which optical properties can be locally analyzed. Both local electronic structures and optical properties revealed gradients within the grain boundary cores of both investigated interfaces. The results show that even in the presence of atomically structured grain boundary …

High-Resolution Imaging Of Proteins In Human Teeth By Scanning Probe Microscopy, Alexei Gruverman, D. Wu, B. J. Rodriguez, Sergei V. Kalinin, S. Habelitz

Alexei Gruverman Publications

High-resolution studies of dental tissues are of considerable interest for biomedical engineering and clinical applications. In this paper, we demonstrate the application of piezoresponse force microscopy (PFM) to nanoscale imaging of internal structure of human teeth by monitoring the local mechanical response to an electrical bias applied via a conductive tip. It is shown that PFM is capable of detecting dissimilar components of dental tissues, namely, proteins and calcified matrix, which have resembling morphology but different piezoelectric properties. It is demonstrated that collagen fibrils revealed in chemically treated intertubular dentin exhibit high piezoelectric activity and can be visualized in PFM …

Nondipole Effects In Double Photoionization Of He, A.Y. Istomin, N. L. Manakov, A. V. Meremianin, Anthony F. Starace

Anthony F. Starace Publications

Lowest-order nondipole effects are studied in double photoionization (DPI) of the He atom. Ah initio parametrizations of the quadrupole transition amplitude for DPI from the ¹S₀state are presented in terms of the exact two-electron reduced matrix elements. Parametrizations for the dipole-quadrupole triply differential cross section (TDCS) and doubly differential cross section (DDCS) are presented in terms of polarization-independent amplitudes for the case of an elliptically polarized photon. Expressions for the DDCS in terms of the reduced two-electron matrix elements are also given. A general analysis of retardation-induced asymmetries of the TDCS including the circular dichroism effect at …

X-Ray/Ultraviolet Observing Campaign Of The Markarian 279 Active Galactic Nucleus Outflow: A Close Look At The Absorbing/Emitting Gas With Chandra-Letgs, E. Constantini, Jelle S. Kaastra, Nahum Arav, Gerard A. Kriss, K.C. Steenbrugge, Jack R. Gabel, F. Verbunt, Ehud Behar, C. Martin Gaskell, Kirk T. Korista, Daniel Proga, Jessica Kim-Quijano, J.E. Scott, Elizabeth S. Klimek, C.H. Hedrick

C. Martin Gaskell Publications

We present a Chandra-LETGS observation of the Seyfert 1 galaxy Mrk 279. This observation was carried out simultaneously with HST-STIS and FUSE, in the context of a multiwavelength study of this source. The Chandra pointings were spread over ten days for a total exposure time of ~360 ks. The maximal continuum flux variation is of the order of 30%. The spectrum of Mrk 279 shows evidence of broad emission features, especially at the wavelength of the O VII triplet. We quantitatively explore the possibility that this emission is produced in the broad line region (BLR). We modeled the broad …

Evidence For Two Kinematically Distinct Broad Emission Line Producing Regions In Active Galactic Nuclei, Stephanie A. Snedden, C. Martin Gaskell

C. Martin Gaskell Publications

We present the results of an analysis of line profiles of high- and low-ionization broad emission lines in 8 AGNs observed by the Hubble Space Telescope. We derive the physical conditions in the gas as a function of velocity. We find no evidence for a separate intermediate line region. For the broad line region as a whole we find a major contradiction between the velocity dependencies of conditions deduced from the major high-ionization lines and those deduced from the hydrogen lines alone if they are assumed to come from the same gas clouds. The hydrogen lines imply that the density …

Threshold Effects In Strong-Field Detachment Of H- And F-: Plateau Enhancements And Angular Distribution Variations, Katarzyna Krajewska, Ilya I. Fabrikant, Anthony F. Starace

Anthony F. Starace Publications

Above-threshold detachment (ATD) rates for H¹ and F¹ ions in the high-energy plateau region are calculated as functions of photon number and laser intensity by solving the time-dependent Schrödinger equation within the Sturmian-Floquet approach. Pronounced enhancements of the ATD rates are found (up to an order of magnitude) as the laser-field intensity passes across ponderomotive-potential-induced channel closings. We confirm the zero-range potential model results of Borca et al. [Phys. Rev. Lett. 88, 193001 (2002)] for negative ions whose initial states have s symmetry, and we investigate here the case of initial states having p symmetry. Depending on …

Measurement Of The Cp-Violation Parameter Of B0 Mixing And Decay With Pp̅ → ΜμX Data, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Kenneth Bloom Publications

We measure the dimuon charge asymmetry A in pp̅ collisions at a center of mass energy √s =1960 GeV. The data was recorded with the D0 detector and corresponds to an integrated luminosity of approximately 1:0 fb^-1. Assuming that the asymmetry A is due to asymmetric B⁰ ↔ B̅ mixing and decay, we extract the CP-violation parameter of B⁰ mixing and decay: [ℜ(∊_B⁰)]/[1+∣∊_B⁰∣² = (A_B⁰)/4 = -0.0023 ± 0.0011 (stat) ± 0.0008(syst). A_B⁰ is the dimuon charge asymmetry from decays of B …

Experimental Observation Of Nonlinear Thomson Scattering, Szu-Yuan Chen, Anatoly Maksimchuk, Donald Umstadter

Donald Umstadter Publications

A century ago, J. J. Thomson showed that the scattering of low-intensity light by electrons was a linear process (i.e., the scattered light frequency was identical to that of the incident light) and that light’s magnetic field played no role. To- day, with the recent invention of ultra-high-peak- power lasers it is now possible to create a sufficient photon density to study Thomson scattering in the relativistic regime. With increasing light intensity, electrons quiver during the scattering process with increasing velocity, approaching the speed of light when the laser intensity approaches 10¹⁸ W/cm². In this limit, the …

Decoherence And Recoherence In A Vibrating Rf Squid, Eyal Buks, M. P. Blencowe

Dartmouth Scholarship

We study an rf SQUID, in which a section of the loop is a freely suspended beam that is allowed to oscillate mechanically. The coupling between the rf SQUID and the mechanical resonator originates from the dependence of the total magnetic flux threading the loop on the displacement of the resonator. Motion of the latter affects the visibility of Rabi oscillations between the two lowest energy states of the rf SQUID. We address the feasibility of experimental observation of decoherence and recoherence, namely decay and rise of the visibility, in such a system.