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Complete Single-Ionization Momentum Spectra For Strong Perturbation Collisions, Ronald E. Olson, C. J. Wood, H. Schmidt-Böcking, R. Moshammer, J. Ullrich Jan 1998

Complete Single-Ionization Momentum Spectra For Strong Perturbation Collisions, Ronald E. Olson, C. J. Wood, H. Schmidt-Böcking, R. Moshammer, J. Ullrich

Physics Faculty Research & Creative Works

The combination of recoil ion and ionized electron momentum spectroscopy provides an unparalleled method to investigate the details of ion-atom collision dynamics in kinematically complete experiments. To predict single ionization scattering behavior at the level now realized by experiment, the classical trajectory three-body Monte Carlo method has been used to obtain complete momenta information for the ionized electron, recoil ion, and projectile in the collision plane defined by the incident projectile and outgoing recoil ion. Strongly coupled systems were considered where the charge state of the projectile divided by the speed of the collision [Formula Presented] is greater than unity. …


Ionization Dynamics In Fast Ion-Atom Collisions. Ii. Final-State Momentum Distributions Of The Ionization Products In Collisions Of He With Bare Carbon Ions, Lokesh C. Tribedi, P. Richard, Y. D. Wang, C. D. Lin, Ronald E. Olson, L. Gulyas Jan 1998

Ionization Dynamics In Fast Ion-Atom Collisions. Ii. Final-State Momentum Distributions Of The Ionization Products In Collisions Of He With Bare Carbon Ions, Lokesh C. Tribedi, P. Richard, Y. D. Wang, C. D. Lin, Ronald E. Olson, L. Gulyas

Physics Faculty Research & Creative Works

We have used the energy and angular distributions of the low-energy electron emission cross sections from the preceding paper [Lokesh C. Tribedi et al., Phys. Rev. A 58, 3619 (1998)] to derive the doubly differential final-state longitudinal momentum distributions of the electrons, recoil ions, and projectiles in ion-atom ionization for [Formula Presented] The complementary nature of the electron spectroscopy and the recoil-ion momentum spectroscopy have been investigated using a formulation based on three-body kinematics to explore the ionization dynamics in detail. The influence of the three-body ionization as well as the binary-encounter processes on the recoil-ion (and projectile) longitudinal momentum …


Effect Of Exchange Interactions At Antiferromagnetic/Ferromagnetic Interfaces On Exchange Bias And Coercivity, D. Dimitrov, Shufeng Zhang Jan 1998

Effect Of Exchange Interactions At Antiferromagnetic/Ferromagnetic Interfaces On Exchange Bias And Coercivity, D. Dimitrov, Shufeng Zhang

Physics Faculty Research & Creative Works

We report on the correlation between unidirectional and uniaxial anisotropy in exchange-biased ferromagnetic Permalloy layers. The dependence of exchange bias and coercivity on temperature and the antiferromagnetic and ferromagnetic layer thickness was studied and compared with the predictions of different theoretical models. A thorough explanation of the experimental data is provided by theoretical extension of Malozemoff's model. © 1998 The American Physical Society.


Hierarchical Search Strategy For The Detection Of Gravitational Waves From Coalescing Binaries: Extension To Post-Newtonian Waveforms, Soumya Mohanty Jan 1998

Hierarchical Search Strategy For The Detection Of Gravitational Waves From Coalescing Binaries: Extension To Post-Newtonian Waveforms, Soumya Mohanty

Physics & Astronomy Faculty Publications

The detection of gravitational waves from coalescing compact binaries would be a computationally intensive process if a single bank of template wave forms (one step search) is used. In an earlier paper we presented a detection strategy, called a two step search, that utilizes a hierarchy of template banks. It was shown that in the simple case of a family of Newtonian signals, an on-line two step search was ≃8 times faster than an on-line one step search (for the initial LIGO). In this paper we extend the two step search to the more realistic case of …


Atomic Hydrogen Cleaning Of Inp(100) For Preparation Of A Negative Electron Affinity Photocathode, K. A. Elamrawi, M. A. Hafez, H. E. Elsayed-Ali Jan 1998

Atomic Hydrogen Cleaning Of Inp(100) For Preparation Of A Negative Electron Affinity Photocathode, K. A. Elamrawi, M. A. Hafez, H. E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

Atomic hydrogen cleaning is used to clean InP(100) negative electron affinity photocathodes. Reflection high-energy electron diffraction patterns of reconstructed, phosphorus-stabilized, InP(100) surfaces are obtained after cleaning at ∼400 °C. These surfaces produce high quantum efficiency photocathodes (∼8.5%), in response to 632.8 nm light. Without atomic hydrogen cleaning, activation of InP to negative electron affinity requires heating to ∼530 °C. At this high temperature, phosphorus evaporates preferentially and a rough surface is obtained. These surfaces produce low quantum efficiency photocathodes (∼0.1%). The use of reflection high-energy electron diffraction to measure the thickness of the deposited cesium layer during activation by correlating …


Stress And Structure Of Ni Monolayers On W(110): The Importance Of Lattice Mismatch, D. Sander, C. Schmidthals, Axel Enders, J. Kirschner Jan 1998

Stress And Structure Of Ni Monolayers On W(110): The Importance Of Lattice Mismatch, D. Sander, C. Schmidthals, Axel Enders, J. Kirschner

Axel Enders Publications

The combination of in situ stress measurements, low-energy electron diffraction, and scanning tunneling microscopy reveals the intimate relation between film structure and film stress for epitaxial growth of Ni on W(110) in the monolayer range. In contradiction to lattice mismatch considerations, we measure tremendous compressive stress in the pseudomorphic Ni film, where tensile film stress is expected from strain arguments. Surface stress of the film-substrate composite is proposed to be much more relevant for the description of film stress in the submonolayer range than lattice mismatch arguments are.


Critical Point In Ferroelectric Langmuir-Blodgett Polymer Films, Stephen Ducharme, A.V. Bune, L.M. Blinov, V.M. Fridkin, S.P. Palto, A.V. Sorokin, S.G. Yudin Jan 1998

Critical Point In Ferroelectric Langmuir-Blodgett Polymer Films, Stephen Ducharme, A.V. Bune, L.M. Blinov, V.M. Fridkin, S.P. Palto, A.V. Sorokin, S.G. Yudin

Stephen Ducharme Publications

The ferroelectric critical point has been found in a ferroelectric polymer by exploring the influence of the electric field on the paraelectric-ferroelectric phase transition. Dielectric and pyroelectric measurements on 30-monolayer-thick films of the crystalline copolymer poly(vinylidene fluoride-trifluoroethylene) grown by Langmuir-Blodgett deposition show a single hysteresis loop below the zero-field phase transition temperature Tc0=80±10 °C, double hysteresis loops between Tc0 , and the critical temperature Tcr=145±5 °C, and no hysteresis above Tcr where the critical electric field is Ecr=0.93±0.1X109 V/m.


Electron Attachment Energies Of The Dna Bases, Kayvan Aflatooni, Gordon A. Gallup, Paul Burrow Jan 1998

Electron Attachment Energies Of The Dna Bases, Kayvan Aflatooni, Gordon A. Gallup, Paul Burrow

Paul Burrow Publications

Injection of electrons into the empty π* molecular orbitals of uracil and the DNA bases creates short-lived anion states whose energies have been determined by electron scattering. A common range of attachment energies into the lowest orbitals is observed in all the bases. Evidence for nuclear motion during the lifetimes of the anions is found in all the compounds except adenine. These properties of the bases as bridge sites along the π-stack of DNA, namely, the effective degeneracy of the anion energies and the strong excitation of vibration, are key parameters for theories of electron-transfer rate, some of …


Measurements Of The Meson-Photon Transition Form Factors Of Light Pseudoscalar Mesons At Large Momentum Transfer, J. Gronberg, Kenneth A. Bloom, Cleo Collaboration Jan 1998

Measurements Of The Meson-Photon Transition Form Factors Of Light Pseudoscalar Mesons At Large Momentum Transfer, J. Gronberg, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

Using the CLEO II detector, we have measured the differential cross sections for exclusive two-photon production of light pseudoscalar mesons π0, η, and η′. From our measurements we have obtained the form factors associated with the electromagnetic transitions γ*γ → meson. We have measured these form factors in the momentum transfer ranges from 1.5 to 9, 20, and 30 GeV2 for π0, η, and η′, respectively, and have made comparisons to various theoretical predictions.


Mach-Zehnder Interferometer Fringe Projector For Variable Resolution Video Moire, Phillip C. Kalmanson, August Schutte, Chris L. Hart, Joel H. Blatt Jan 1998

Mach-Zehnder Interferometer Fringe Projector For Variable Resolution Video Moire, Phillip C. Kalmanson, August Schutte, Chris L. Hart, Joel H. Blatt

Aerospace, Physics, and Space Science Faculty Publications

A Mach-Zehnder based variable resolution fringe projection system has been built for 3-D video moini machine vision. This system uses the three main advantages of the Mach-Zehnder - 1) There is no optical feedback to the laser source, 2) The interfemmeter can accept two different laser wavelengths simultaneously, and 3) The interferometer produces two orthngonal output beams. The lack of optical feedback makes the Mach-Zehnder especially attractive for use with high power laser diode sources which are sensitive to optical feedback. When the two input ports axe used with two different wavelength lasers, the target can be illuminated by simultaneous …


The Effect Of Temperature Dependent Frequency Factor On The Evaluated Trapping Parameters Of Tsl Glow Curves, A. N. Yazici, Z. Öztürk Jan 1998

The Effect Of Temperature Dependent Frequency Factor On The Evaluated Trapping Parameters Of Tsl Glow Curves, A. N. Yazici, Z. Öztürk

Turkish Journal of Physics

The effect of temperature dependency on frequency factor and its relationship to trapping parameters is discussed by using the peak shape method. The coefficients appearing in the peak shape formula for the calculation of the activation energy have been determined and tabulated for the symmetry factor $\mu_g(X)$ for $x=0.50$ and 0.75 of the peak intensity. It is found that significant errors occur in the value of the trapping parameters if the temperature dependecy of the frequency factor is not consider.


A Time-Dependent Quantum Study Of Li+Hf(\Nu=1) -> Lif(\Nu')+H, Fahrettin Gögtaş, Gabriel G. Balint-Kurti Jan 1998

A Time-Dependent Quantum Study Of Li+Hf(\Nu=1) -> Lif(\Nu')+H, Fahrettin Gögtaş, Gabriel G. Balint-Kurti

Turkish Journal of Physics

Time-dependent quantum wave packet calculations are performed for a model based (two-dimensional) $Li+HF(\nu=1)\ra LiF(\nu^{\prime})+H$ reaction. The reaction probabilities for a broad range of collison energies are calculated by a single solution of the time-dependent Schr\\"{o}dinger equation. The calculated reaction probabilities show many sharp features as a function of energy which are ascribed to scattering resonances.


Fine Structure Analysis Of 4702 ^Oa Band Of The Molecule, M.B. Sureshkumar, S.R. Srikant Jan 1998

Fine Structure Analysis Of 4702 ^Oa Band Of The Molecule, M.B. Sureshkumar, S.R. Srikant

Turkish Journal of Physics

The emission spectrum of the cobalt monochloride molecule has been excited in a high frequency discharge tube source and the (0,0) band of H-system at 4702 \AA was photo-graphed at an inverse dispersion of 0.973 \AA/mm in the 5th order of a two meter plane grating spectrograph (Carl-Zeiss). The fine structure analysis of the band has been carried out and the molecular constants are reported for the first time. Rotational isotopic shift due to $^{37}$Cl support the analysis. The electronic transition involved is of the type $0^-$----- $0^-$ of case (c) which is equivalent of $^{3}\sum^{+}$-----$^{3}\sum^+$ or $^5\sum^+$-----$^5\sum^+$.


A Study Of The Linbo_3 And Litao_3 Absorption Edge, S. Çabuk, A. Mamedov Jan 1998

A Study Of The Linbo_3 And Litao_3 Absorption Edge, S. Çabuk, A. Mamedov

Turkish Journal of Physics

Optical spectroscopy methods are used to study the spectra of some oxygen-octahedral ferroelectrics - $LiNbO_3$ and $LiTaO_3$. Study of the role of $BO_6$ octahedron by using spectroscopic methods can cast light on the many physical phenomena that place in $LiNbO_3$ and $LiTaO_3$. For these crystals, absorption edge, band gap, Urbach constants and phonon energy were found.


A Study On The Effect Of Ni Dopping On Bi-Pb-Sr-Ca-Cu-O System, M. Tepe, D. Abukay Jan 1998

A Study On The Effect Of Ni Dopping On Bi-Pb-Sr-Ca-Cu-O System, M. Tepe, D. Abukay

Turkish Journal of Physics

The effect of $Ni$ doping on superconductivity properties of the $Bi_{1.7}Pb_{0.3}Sr_2Ca_2(Cu_{1-x}Ni_x)_3O_y$ system has been investigated by means of $x$-ray diffraction, ac electrical resistance, ac magnetic susceptibility and critical current measurements. The volume fraction of the 2223 phase decreases with increasing $Ni$ concentration. The zero-resistance temperature and the critical current density are suppressed with $Ni$ substitution.


Characterization Of Sb Doped Y Bacuo Superconducting Ceramics, K. Kocabaş, N. Kazanci, M. Tepe Jan 1998

Characterization Of Sb Doped Y Bacuo Superconducting Ceramics, K. Kocabaş, N. Kazanci, M. Tepe

Turkish Journal of Physics

In this study the structural characteristics of $Sb_2O_3$ doped $YBa_2Cu_3O_{7-x}$ superconductive ceramics are investigated by electrical and XRD analyses. It is determined that, while in undoped specimens the value of $T_c$ is equal to 92 K, this value is negatively influenced by the addition of $Sb$. Structural phase results obtained from XRD analysis confirm the result obtained from the electrical measurements.


Microscopic Calculations Of The Nucleus-Nucleus Optical Potential, M. M. Osman Jan 1998

Microscopic Calculations Of The Nucleus-Nucleus Optical Potential, M. M. Osman

Turkish Journal of Physics

In present work, a density dependent nucleon-nucleon interactions based on the $G$-matrix elements of the Paris nucleon-nucleon potential have been used to calculate the real part of the nucleus-nucleus optical potential. We have compared our results with those deduced from experiment. We found that our results, obtained using a suitable approximation of the kinetic energy density, agree satisfactory with those extracted from experiment at the strong absorption radius. Moreover, the higher values of the compressibility, $K$, agree better with experiment than the lower values.


Remote Sensing And Synchronous Land Surface Measurements Of Soil Moisture And Soil Temperature In The Field, N.V. Kolev, K.P. Penev, Y.M. Kirkova, B.S. Krustanov, T.G. Nazarsky, G.K. Dimitrov, C.P. Levchev, H.I. Prodanov, L.H. Kraleva Jan 1998

Remote Sensing And Synchronous Land Surface Measurements Of Soil Moisture And Soil Temperature In The Field, N.V. Kolev, K.P. Penev, Y.M. Kirkova, B.S. Krustanov, T.G. Nazarsky, G.K. Dimitrov, C.P. Levchev, H.I. Prodanov, L.H. Kraleva

Turkish Journal of Physics

The paper presents the results of remote sensing and synchronous land surface measurements for estimation of soil (surface and profile) water content and soil temperature for different soil types in Bulgaria. The relationship between radiometric temperature and soil surface water content is shown. The research is illustrated by some results from aircraft and land surface measurements carried out over three test areas near Pleven, Sofia and Plovdiv, respectively, during the period 1988-1990.


Deformation Methods For Investigation Of The Deep Level Parameters In Semiconductors, S. Z. Zainabidinov, A. Abduraimov, O. O. Mamatkarimov, I.G. Tursunov, R.Kh. Khamidov Jan 1998

Deformation Methods For Investigation Of The Deep Level Parameters In Semiconductors, S. Z. Zainabidinov, A. Abduraimov, O. O. Mamatkarimov, I.G. Tursunov, R.Kh. Khamidov

Turkish Journal of Physics

In this paper deformation methods are offered to investigate deep level parameters in semiconductors. It is based on strain parameters measurements of compensated and overcompensated semiconductors. The dynamic changes of current flow in compensated and overcompensated samples of $p$-type $Si: Ni$ and $n$-type $Si: Mn$ under uniform pulse hydrostatic compression (UHC) was investigated. It was observed that in $p$-type $Si: Ni$ samples ionization energy levels $Ni$ at UHC increases, on the contrary in samples $n$-type $Si: Mn$ it decreases. The ionization energy and baric coefficient of the shift of $Ni$ and $Mn$ levels were bounded.


Modelling Of Radiation Regime Receiver Cavities Of Solar Power Plants, Eduard Avanesov, Nina Berezhnaya Jan 1998

Modelling Of Radiation Regime Receiver Cavities Of Solar Power Plants, Eduard Avanesov, Nina Berezhnaya

Turkish Journal of Physics

In this work, we develop a model for radiant heat transfer calculations inside spherical and cylindrical spaces. The analysis of the possibility of mirror cone subreflector applications for uniform flux density attainment is carried out. A procedure optimizing equiilluminate space forming a search for an indicatrix's composition is developed.


Anomalous Electrical Characteristics Of Ion Implanted P^+-N Juntions, N. Siddiqui Jan 1998

Anomalous Electrical Characteristics Of Ion Implanted P^+-N Juntions, N. Siddiqui

Turkish Journal of Physics

Electrical characteristics of three $P^+ - n$ diodes fabricated on high resistivity silicon by ion implantation technique are studied by making capacitance-voltage (C-V), reverse current-voltage (I-V) and dielectric spectroscopy of semiconductor (DSS) measurements. The C-V characteristics show abrupt fall in capacitance, while I-V characteristics show abrupt rise in current at the same voltages as in the C-V characteristics. These abrupt discontinuities are ascribed to the formation of defect clusters in the lightly doped base regions where charge transfer might be taking place by thermally assisted tunneling. Low activation energies obtained in the DSS measurements also point toward the same mechanism.


Electro-Optic Response Of A Polymer Dispersed Liquid Crystal Film, Rıdvan Karapinar Jan 1998

Electro-Optic Response Of A Polymer Dispersed Liquid Crystal Film, Rıdvan Karapinar

Turkish Journal of Physics

Polymer dispersed liquid crystal (PDLC) films are potentially useful in electro-optic devices since they can be used for vision products. In this work the PDLC thin films were prepared by a photopolymerization induced phase separation method and electro-optic properties of the films were investigated.


Reorientation Of Magnetization In Thin Films, Bengü Kaplan Jan 1998

Reorientation Of Magnetization In Thin Films, Bengü Kaplan

Turkish Journal of Physics

The spin wave energy is determined by the competition between uniaxial and cubic anisotropy. We discuss the reorientation temperature $ T_{R} $ of magnetization in two-dimension and calculate its dependence on the exchange, $J$, and the uniaxial anisotropy, $G$, parameters within random phase approximation. We find that $ T_{R} $ varies as $ \sqrt{JG} $ in the planar regime.


Photoconductivity Studies Of Crystalline Si:H P-I-N, Ruhi Kaplan, Bengü Kaplan Jan 1998

Photoconductivity Studies Of Crystalline Si:H P-I-N, Ruhi Kaplan, Bengü Kaplan

Turkish Journal of Physics

Optically modulated photoconductivity (PC) properties of hydrogenated crystalline silicon (c-Si:H) with p-i-n junctions were investigated by frequency-resolved spectroscopy in the temperature range 20-290 K. The PC lifetime measurements of c-Si:H p-i-n show a second lifetime distribution which only dominates at low temperature under low illumination levels of excitation. Unlike the room temperature single lifetime distribution seen in c-Si:H p-i-n, the maximum of this second lifetime distribution shifts to longer times when the excitation intensity decreases, which reconciles with non-geminate pair recombination and thus the distant-pair model. In addition to lifetime measurements, the direct current-voltage (I-V) characteristics, the excitation light intensity- …


The Image Reconstruction By Photocounts Triple Correlations, R. R. Vildanov, M. S. Ismatov, N. Z. Kodirov, A. T. Mirzaev, A. N. Yakubov Jan 1998

The Image Reconstruction By Photocounts Triple Correlations, R. R. Vildanov, M. S. Ismatov, N. Z. Kodirov, A. T. Mirzaev, A. N. Yakubov

Turkish Journal of Physics

An optoelectronic system is constructed for the recording of the triple correlation function for radiation intensity being detected in a photon counting operation. The results of the investigation show the possibility an image reconstruction for faint objects from the derivation of comprehensive information related to the coherence function.


Optical Anisotropy Of Iron Garnets With Growing Anisotropy, Odil Ochilov Jan 1998

Optical Anisotropy Of Iron Garnets With Growing Anisotropy, Odil Ochilov

Turkish Journal of Physics

The theoretical analysis of the position of principal diachronic directions at magnetization rotation in (100) and (110) planes for the case of growing dichroism axes in random directions was made. The calculations of angular dependencies of dichroic axes (DA) position for different values of the magneto-optical anisotropy parameter, a, have been done. The relations between the growing and magneto-optical dichroism, K/M, and the angle \delta characterizing the direction of principal growing dichroism axes were given. The angular dependences of DA position in epitaxial iron garnet films have been investigated experimentally. The measurements at the different light wavelengths permitted one to …


Analytical Expressions Of Matrix Elements For Saxon-Woods Potential And Pad'{E} Approximations, Valentin L. R. Niculescu, Dumitru Catana Jan 1998

Analytical Expressions Of Matrix Elements For Saxon-Woods Potential And Pad'{E} Approximations, Valentin L. R. Niculescu, Dumitru Catana

Turkish Journal of Physics

The paper presents the analytical matrix elements of the kinetic hamiltonian in the oscillator base. The Pad'{e} approximations for the potential part (Saxon - Woods and alike) was used. From residue calculus the potential matrix elements are analytical. Many parts of these expressions can be computed once for ever. In this way the evaluation time can be reduced and the relations obtained are well suited for parallel computation.


Alloying Of Aisi 1008 Steel Surfaces By 10ms Nd: Yag Laser Pulses, Raid A. İsmai̇l Jan 1998

Alloying Of Aisi 1008 Steel Surfaces By 10ms Nd: Yag Laser Pulses, Raid A. İsmai̇l

Turkish Journal of Physics

Hardened surfaces were produced on AISI 1008 steel through a laser surface alloying (LSA) technique. Mixture of pure Boron, Silicon, and Carbon powders of the same grain size were deposited on the substrate. The surface was then melted using pulsed Nd:YAG laser (\tau = 10 ms) at an energy of 12 J. The influence of alloying elements on the microstructure and hardness of treated layer was investigated. Dependending on the alloying elements species, different maximum surface hardness, different maximum depth, and different hardness profile could be obtained. The B+Si alloyed zone exhibited maximum hardness to a nominal alloying depth of …


Infrared Absorption Study Of Potassium-Boro-Vanadate-Iron Glasses, Dinesh K. Kanchan, Harshvadan R. Panchal Jan 1998

Infrared Absorption Study Of Potassium-Boro-Vanadate-Iron Glasses, Dinesh K. Kanchan, Harshvadan R. Panchal

Turkish Journal of Physics

The IR studies have been made in the K_2O-B_2O_3-V_2O_5-Fe_2O_3 glass system. The increase in intensity and shifting of vibrational bands towards lower wave number at 1400-1350 cm^{-1}, 1200 cm^{-1} and 100-940 cm^{-1} in IR spectra have been ascribed to the formation of BO_3 to BO_4 and VO_5 to VO_4 tetrahedra along with the formation of non-bridging oxygens attached to boron and vanadium. In heat-treated glass samples, many new vibrational bands have been observed which were however, absent in the untreated samples. The preservation of the 1020 cm^{-1} band assigned to V=O bond suggests that K_2O shows the preference for borate …


Domain Structures Of Epitaxial Perovskite Ferroelectric Films: Part Ii. Applications, S. Pamir Alpay, Alexander L. Roytburd Jan 1998

Domain Structures Of Epitaxial Perovskite Ferroelectric Films: Part Ii. Applications, S. Pamir Alpay, Alexander L. Roytburd

Turkish Journal of Physics

The use of domain stability maps for epitaxial perovskite ferroelectric films is illustrated with some examples. The equilibrium domain structure and domain fractions as a function of temperature are predicted for PbTiO_3(001) films grown epitaxially on three different substrates: MgO(001), KTaO_3(001), and SrTiO_3(001). Misfit dislocation formation at the growth temperature is found to have a profound effect on both the domain selection and relative domain populations. Theoretical predictions are compared with available experimental data.