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Selected Works

2018

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Articles 1 - 30 of 164

Full-Text Articles in Physics

Theoretical Studies Of Ultrafast Electron Dynamics In Atoms And Molecules Via High-Order Harmonic Generation, Paul Abanador Dec 2018

Theoretical Studies Of Ultrafast Electron Dynamics In Atoms And Molecules Via High-Order Harmonic Generation, Paul Abanador

Paul Abanador

The interaction of atoms and molecules with strong laser pulses is of fundamental interest in physics and chemistry. Notably, the process known as high-order harmonic generation (HHG) refers to the production of extreme-ultraviolet (XUV) light, which occurs when an ensemble of atoms or molecules is subjected to a strong infrared laser field. Characterized by an attosecond time scale (1 as = 10^-18 s), the HHG process provides the capability for experimental measurements to capture the ultrafast motion of electrons in these target atoms and molecules. The underlying physical mechanism behind this process naturally leaves imprints in the properties of the ...


Interactions Between Disciplinary Practices And Joint Work In Undergraduate Physics Research Experiences, Gina M. Quan, Chandra Turpen, Andrew Elby Dec 2018

Interactions Between Disciplinary Practices And Joint Work In Undergraduate Physics Research Experiences, Gina M. Quan, Chandra Turpen, Andrew Elby

Gina Quan

We analyze how participating in undergraduate research experiences (UREs) influenced physics students’ trajectories of participation within the community of practice of physics researchers. Students in the study participated in an elective seminar in which they were paired with graduate student and faculty mentors on physics research projects and participated in weekly discussions about research. Using video data from student interviews and mentor interviews, we characterize two aspects of students’ engagement in the physics community of practice. First, we find variations in their engagement in physics practice, which we characterize as physics activities that are connected and purposeful. Second, we characterize ...


Generating High-Order Optical And Spin Harmonics From Ferromagnetic Monolayers, G.P. Zhang, M.S. Si, M. Murakami, Y.H. Bai, Thomas F. George Nov 2018

Generating High-Order Optical And Spin Harmonics From Ferromagnetic Monolayers, G.P. Zhang, M.S. Si, M. Murakami, Y.H. Bai, Thomas F. George

Thomas George

High-order harmonic generation (HHG) in solids has entered a new phase of intensive research, with envisioned band-structure mapping on an ultrashort time scale. This partly benefits from a flurry of new HHG materials discovered, but so far has missed an important group. HHG in magnetic materials should have profound impact on future magnetic storage technology advances. Here we introduce and demonstrate HHG in ferromagnetic monolayers. We find that HHG carries spin information and sensitively depends on the relativistic spin–orbit coupling; and if they are dispersed into the crystal momentum k space, harmonics originating from real transitions can be k-resolved ...


Time-Resolved Double-Resonance Spectroscopy: Lifetime Measurement Of The 61Σ+G(7,31) Electronic State Of Molecular Sodium, Michael Saaranen, Dinesh Wagle, Emma Mclaughlin, Amelia Paladino, Seth T. Ashman, Burcin Bayram Nov 2018

Time-Resolved Double-Resonance Spectroscopy: Lifetime Measurement Of The 61Σ+G(7,31) Electronic State Of Molecular Sodium, Michael Saaranen, Dinesh Wagle, Emma Mclaughlin, Amelia Paladino, Seth T. Ashman, Burcin Bayram

Seth Ashman

We report on the lifetime measurement of the 61Σ+g(7,31) state of Na2 molecules, produced in a heat-pipe oven, using a time-resolved spectroscopic technique. The 61Σ+g(7,31) level was populated by two-step two-color double resonance excitation via the intermediate A1Σ+u(8,30) state. The excitation scheme was done using two synchronized pulsed dye lasers pumped by a Nd:YAG laser operating at the second harmonics. The fluorescence emitted upon decay to the final state was measured using a time-correlated photon counting technique, as a function of argon pressure. From this, the radiative lifetime was extracted ...


Tim_Rinn_Final_Disertation.Pdf, Timothy T. Rinn Nov 2018

Tim_Rinn_Final_Disertation.Pdf, Timothy T. Rinn

Timothy Rinn

No abstract provided.


Role Of The Recoil Ion In Single-Electron Capture And Single-Ionization Processes For Collisions Of Protons With He And Ar Atoms, P. Focke, Ronald E. Olson, N. D. Cariatore, M. Alessi, S. Otranto Nov 2018

Role Of The Recoil Ion In Single-Electron Capture And Single-Ionization Processes For Collisions Of Protons With He And Ar Atoms, P. Focke, Ronald E. Olson, N. D. Cariatore, M. Alessi, S. Otranto

Ronald E. Olson

In this work the single-electron capture and single-ionization processes are studied for proton collisions with He and Ar atoms at impact energies in the range 25–100 keV. Classical trajectory Monte Carlo simulations are benchmarked against experimental data obtained at the reaction microscope in Bariloche, Argentina, which employs the cold target recoil-ion momentum spectroscopy technique. Special emphasis is placed on describing the momentum transfer to the recoil ion for these collision systems.


Dhital_Pnas.Pdf, Chetan Dhital Oct 2018

Dhital_Pnas.Pdf, Chetan Dhital

Chetan Dhital

No abstract provided.


Inverse Design Of Perfectly Transmitting Eigenchannels In Scattering Media, Milan Koirala, Raktim Sarma, Hui Cao, Alexey Yamilov Oct 2018

Inverse Design Of Perfectly Transmitting Eigenchannels In Scattering Media, Milan Koirala, Raktim Sarma, Hui Cao, Alexey Yamilov

Alexey Yamilov

Light-matter interactions inside a turbid medium can be controlled by tailoring the spatial distribution of energy density throughout the system. Wavefront shaping allows selective coupling of incident light to different transmission eigenchannels, producing dramatically different spatial intensity profiles. In contrast to the density of transmission eigenvalues that is dictated by the universal bimodal distribution, the spatial structures of the eigenchannels are not universal and depend on the confinement geometry of the system. Here, we develop and verify a model for the transmission eigenchannel with the corresponding eigenvalue close to unity. By projecting the original problem of two-dimensional diffusion in a ...


Enhanced Optical Coupling And Raman Scattering Via Microscopic Interface Engineering, Jonathan V. Thompson, Brett H. Hokr, Wihan Kim, Charles W. Ballmann, Brian E. Applegate, Javier Jo, Alexey Yamilov, Hui Cao, Marlan O. Scully, Vladislav V. Yakovlev Oct 2018

Enhanced Optical Coupling And Raman Scattering Via Microscopic Interface Engineering, Jonathan V. Thompson, Brett H. Hokr, Wihan Kim, Charles W. Ballmann, Brian E. Applegate, Javier Jo, Alexey Yamilov, Hui Cao, Marlan O. Scully, Vladislav V. Yakovlev

Alexey Yamilov

Spontaneous Raman scattering is an extremely powerful tool for the remote detection and identification of various chemical materials. However, when those materials are contained within strongly scattering or turbid media, as is the case in many biological and security related systems, the sensitivity and range of Raman signal generation and detection is severely limited. Here, we demonstrate that through microscopic engineering of the optical interface, the optical coupling of light into a turbid material can be substantially enhanced. This improved coupling facilitates the enhancement of the Raman scattering signal generated by molecules within the medium. In particular, we detect at ...


Enhanced Coupling Of Light Into A Turbid Medium Through Microscopic Interface Engineering, Jonathan V. Thompson, Brett H. Hokr, Wihan Kim, Charles W. Ballmann, Brian E. Applegate, Javier Jo, Alexey Yamilov, Hui Cao, Marlan O. Scully, Vladislav V. Yakovlev Oct 2018

Enhanced Coupling Of Light Into A Turbid Medium Through Microscopic Interface Engineering, Jonathan V. Thompson, Brett H. Hokr, Wihan Kim, Charles W. Ballmann, Brian E. Applegate, Javier Jo, Alexey Yamilov, Hui Cao, Marlan O. Scully, Vladislav V. Yakovlev

Alexey Yamilov

There are many optical detection and sensing methods used today that provide powerful ways to diagnose, characterize, and study materials. For example, the measurement of spontaneous Raman scattering allows for remote detection and identification of chemicals. Many other optical techniques provide unique solutions to learn about biological, chemical, and even structural systems. However, when these systems exist in a highly scattering or turbid medium, the optical scattering effects reduce the effectiveness of these methods. In this article, we demonstrate a method to engineer the geometry of the optical interface of a turbid medium, thereby drastically enhancing the coupling efficiency of ...


Electron-Impact Ionization Of H₂O At Low Projectile Energy: Internormalized Triple-Differential Cross Sections In Three-Dimensional Kinematics, Xueguang Ren, Sadek Amami, Khokon Hossen, Esam Ali, Chuangang Ning, James Colgan, Don H. Madison, Andrew Dorn Oct 2018

Electron-Impact Ionization Of H₂O At Low Projectile Energy: Internormalized Triple-Differential Cross Sections In Three-Dimensional Kinematics, Xueguang Ren, Sadek Amami, Khokon Hossen, Esam Ali, Chuangang Ning, James Colgan, Don H. Madison, Andrew Dorn

Don H. Madison

We report a combined experimental and theoretical study of the electron-impact ionization of water (H2O) at the relatively low incident energy of E0=81eV in which either the 1b1 or 3a1 orbitals are ionized leading to the stable H2O cation. The experimental data were measured by using a reaction microscope, which can cover nearly the entire 4π solid angle for the secondary electron emission over a range of ejection energies. We present experimental data for the scattering angles of 6⁰ and 10⁰ for the faster of the two outgoing electrons as a function ...


Natural & Unnatural-Parity Contributions In Electron-Impact Ionization Of Laser-Aligned Atoms, Andrew James Murray, James Colgan, Don H. Madison, Matthew Harvey, Ahmad Sakaamini, James Pursehouse, Kate Nixon, Al Stauffer Oct 2018

Natural & Unnatural-Parity Contributions In Electron-Impact Ionization Of Laser-Aligned Atoms, Andrew James Murray, James Colgan, Don H. Madison, Matthew Harvey, Ahmad Sakaamini, James Pursehouse, Kate Nixon, Al Stauffer

Don H. Madison

Differential cross section measurements from laser-aligned Mg atoms are compared to theoretical calculations using both time dependent and time-independent formalisms. It is found that both natural and unnatural parity contributions to the calculated cross sections are required to emulate the data when the state is aligned out of the scattering plane.


Electron-Impact Ionization Of Laser-Aligned Atoms -- Contributions From Both Natural And Unnatural-Parity States, Andrew James Murray, James Colgan, Don H. Madison, Matthew Harvey, Ahmad Sakaamini Oct 2018

Electron-Impact Ionization Of Laser-Aligned Atoms -- Contributions From Both Natural And Unnatural-Parity States, Andrew James Murray, James Colgan, Don H. Madison, Matthew Harvey, Ahmad Sakaamini

Don H. Madison

Synopsis. The progress of experimental and theoretical measurements for (e,2e) ionization cross sections from laser-aligned atoms is presented here. It is found that both natural and unnatural parity contributions must be included in the models to emulate the experimental data.


(E,2e) Ionization Studies Of N₂ At Low To Intermediate Energies From A Coplanar Geometry To The Perpendicular Plane, Ahmad Sakaamini, Matthew Harvey, Sadek Amami, Andrew James Murray, Don H. Madison, Chuangang Ning Oct 2018

(E,2e) Ionization Studies Of N₂ At Low To Intermediate Energies From A Coplanar Geometry To The Perpendicular Plane, Ahmad Sakaamini, Matthew Harvey, Sadek Amami, Andrew James Murray, Don H. Madison, Chuangang Ning

Don H. Madison

Synopsis. The progress of experimental and theoretical measurements for (e,2e) ionization cross sections from Nitrogen molecules is presented. Results are given for energies from ~10 eV above the ionization potential (IP) through to ~100 eV above the IP for the 3σg, 1πu and 2σg states.


Dynamic Effects In Electron Momentum Spectroscopy Of Sulfur Hexafluoride, Xing Wang, Shenyue Xu, Chuangang Ning, O. Al-Hagan, Pengfei Hu, Yongtao Zhao, Zhongfen Xu, Jingkang Deng, Enliang Wang, Xueguang Ren, Alexander Dorn, Don H. Madison Oct 2018

Dynamic Effects In Electron Momentum Spectroscopy Of Sulfur Hexafluoride, Xing Wang, Shenyue Xu, Chuangang Ning, O. Al-Hagan, Pengfei Hu, Yongtao Zhao, Zhongfen Xu, Jingkang Deng, Enliang Wang, Xueguang Ren, Alexander Dorn, Don H. Madison

Don H. Madison

Electron momentum spectroscopy (EMS) results are presented for the sulfur hexafluoride (SF6) molecule using a high-resolution binary (e, 2e) spectrometer at incident energies (Ei) of 600, 1200, and 2400 eV plus the binding energy. The valence orbital momentum profiles were measured with a binding energy resolution of 0.68 eV and angular resolutions of Δθ = ±0.6⁰, ΔΦ = ±0.85⁰. Whereas the two higher incident energies are in the range where normally EMS measurements do not exhibit an impact-energy dependence, the current experimental data display a dynamic dependence on the impact energies. The measured momentum profiles are compared with predictions ...


Textured Nise₂ Film: Bifunctional Electrocatalyst For Full Water Splitting At Remarkably Low Overpotential With High Energy Efficiency, Abdurazag T. Swesi, Jahangir Masud, Wipula P. R. Liyanage, Siddesh Umapathi, Eric W. Bohannan, Julia E. Medvedeva, Manashi Nath Oct 2018

Textured Nise₂ Film: Bifunctional Electrocatalyst For Full Water Splitting At Remarkably Low Overpotential With High Energy Efficiency, Abdurazag T. Swesi, Jahangir Masud, Wipula P. R. Liyanage, Siddesh Umapathi, Eric W. Bohannan, Julia E. Medvedeva, Manashi Nath

Julia E. Medvedeva

Herein we have shown that electrodeposited NiSe2 can be used as a bifunctional electrocatalyst under alkaline conditions to split water at very low potential by catalyzing both oxygen evolution and hydrogen evolution reactions at anode and cathode, respectively, achieving a very high electrolysis energy efficiency exceeding 80% at considerably high current densities (100 mA cm-2). The OER catalytic activity as well as electrolysis energy efficiency surpasses any previously reported OER electrocatalyst in alkaline medium and energy efficiency of an electrolyzer using state-of-the-art Pt and RuO2 as the HER and OER catalyst, respectively. Through detailed electrochemical and structural ...


Recent Advances In Understanding The Structure And Properties Of Amorphous Oxide Semiconductors, Julia E. Medvedeva, D. B. Buchholz, Robert P. H. Chang Oct 2018

Recent Advances In Understanding The Structure And Properties Of Amorphous Oxide Semiconductors, Julia E. Medvedeva, D. B. Buchholz, Robert P. H. Chang

Julia E. Medvedeva

Amorphous oxide semiconductors (AOSs)--ternary or quaternary oxides of post-transition metals such as In-Sn-O, Zn-Sn-O, or In-Ga-Zn-O–have been known for a decade and have attracted a great deal of attention as they possess several technological advantages, including low-temperature large-area deposition, mechanical flexibility, smooth surfaces, and high carrier mobility that is an order of magnitude larger than that of amorphous silicon (a-Si:H). Compared to their crystalline counterparts, the structure of AOSs is extremely sensitive to deposition conditions, stoichiometry, and composition, giving rise to a wide range of tunable optical and electrical properties. The large parameter space and the resulting ...


Long-Range Tails In Van Der Waals Interactions Of Excited-State And Ground-State Atoms, Ulrich D. Jentschura, V. Debierre Oct 2018

Long-Range Tails In Van Der Waals Interactions Of Excited-State And Ground-State Atoms, Ulrich D. Jentschura, V. Debierre

Ulrich D. Jentschura

A quantum electrodynamic calculation of the interaction of an excited-state atom with a ground-state atom is performed. For an excited reference state and a lower-lying virtual state, the contribution to the interaction energy naturally splits into a pole term and a Wick-rotated term. The pole term is shown to dominate in the long-range limit, altering the functional form of the interaction from the retarded 1/R7 Casimir-Polder form to a long-range tail - provided by the Wick-rotated term - proportional to cos[2(Em - En)R/(ħc)]/R2, where Em < En is the energy of a virtual ...


Scanning Tunneling Spectroscopy Investigations Of Superconducting-Doped Topological Insulators: Experimental Pitfalls And Results, Stefan Wilfert, Paolo Sessi, Zhiwei Wang, Henrik Schmidt, M. Carmen Martínez-Velarte, Seng Huat Lee, Yew San Hor, Alexander F. Otte, Yoichi Ando, Weida Wu, Matthias Bode Oct 2018

Scanning Tunneling Spectroscopy Investigations Of Superconducting-Doped Topological Insulators: Experimental Pitfalls And Results, Stefan Wilfert, Paolo Sessi, Zhiwei Wang, Henrik Schmidt, M. Carmen Martínez-Velarte, Seng Huat Lee, Yew San Hor, Alexander F. Otte, Yoichi Ando, Weida Wu, Matthias Bode

Yew San Hor

Recently, the doping of topological insulators has attracted significant interest as a potential route towards topological superconductivity. Because many experimental techniques lack sufficient surface sensitivity, however, definite proof of the coexistence of topological surface states and surface superconductivity is still outstanding. Here we report on highly surface sensitive scanning tunneling microscopy and spectroscopy experiments performed on Tl-doped Bi2Te3, a three-dimensional topological insulator which becomes superconducting in the bulk at TC=2.3 K. Landau level spectroscopy as well as quasiparticle interference mapping clearly demonstrated the presence of a topological surface state with a Dirac point energy ...


Rotational Symmetry Breaking In A Trigonal Superconductor Nb-Doped Bi₂Se₃, T. Asaba, B. J. Lawson, C. Tinsman, L. Chen, P. Corbae, G. Li, Y. Qiu, Yew San Hor, L. Fu, L. Li Oct 2018

Rotational Symmetry Breaking In A Trigonal Superconductor Nb-Doped Bi₂Se₃, T. Asaba, B. J. Lawson, C. Tinsman, L. Chen, P. Corbae, G. Li, Y. Qiu, Yew San Hor, L. Fu, L. Li

Yew San Hor

The search for unconventional superconductivity has been focused on materials with strong spin-orbit coupling and unique crystal lattices. Doped bismuth selenide (Bi2Se3) is a strong candidate, given the topological insulator nature of the parent compound and its triangular lattice. The coupling between the physical properties in the superconducting state and its underlying crystal symmetry is a crucial test for unconventional superconductivity. In this paper, we report direct evidence that the superconducting magnetic response couples strongly to the underlying trigonal crystal symmetry in the recently discovered superconductor with trigonal crystal structure, niobium (Nb)-doped Bi2Se3 ...


Determination Of The Energy Band Gap Of Bi₂Se₃, G. Martinez, B. A. Piot, M. Hakl, M. Potemski, Yew San Hor Oct 2018

Determination Of The Energy Band Gap Of Bi₂Se₃, G. Martinez, B. A. Piot, M. Hakl, M. Potemski, Yew San Hor

Yew San Hor

Despite intensive investigations of Bi2Se3 in past few years, the size and nature of the bulk energy band gap of this well-known 3D topological insulator still remain unclear. Here we report on a combined magneto-transport, photoluminescence and infrared transmission study of Bi2Se3, which unambiguously shows that the energy band gap of this material is direct and reaches Eg = (220 ± 5) meV at low temperatures.


Robust Odd-Parity Superconductivity In The Doped Topological Insulator NbₓBi₂Se₃, M. P. Smylie, K. Willa, H. Claus, A. Snezhko, I. Martin, W.-K. Kwok, Y. Qiu, Yew San Hor, E. Bokari, P. Niraula, A. Kayani, V. Mishra, U. Welp Oct 2018

Robust Odd-Parity Superconductivity In The Doped Topological Insulator NbₓBi₂Se₃, M. P. Smylie, K. Willa, H. Claus, A. Snezhko, I. Martin, W.-K. Kwok, Y. Qiu, Yew San Hor, E. Bokari, P. Niraula, A. Kayani, V. Mishra, U. Welp

Yew San Hor

We present resistivity and magnetization measurements on proton-irradiated crystals demonstrating that the superconducting state in the doped topological insulator NbxBi2Se3 (x=0.25) is surprisingly robust against disorder-induced electron scattering. The superconducting transition temperature TC decreases without indication of saturation with increasing defect concentration, and the corresponding scattering rates far surpass expectations based on conventional theory. The low-temperature variation of the London penetration depth Δλ(T) follows a power law [Δλ(T)T2] indicating the presence of symmetry-protected point nodes. Our results are consistent with the proposed robust nematic Eu pairing state ...


Nematic Topological Superconducting Phase In Nb-Doped Bi₂Se₃, Junying Shen, Wen-Yu He, Noah Fan Qi Yuan, Zengle Huang, Chang-Woo Cho, Seng Huat Lee, Yew San Hor, Kam Tuen Law, Rolf Lortz Oct 2018

Nematic Topological Superconducting Phase In Nb-Doped Bi₂Se₃, Junying Shen, Wen-Yu He, Noah Fan Qi Yuan, Zengle Huang, Chang-Woo Cho, Seng Huat Lee, Yew San Hor, Kam Tuen Law, Rolf Lortz

Yew San Hor

A nematic topological superconductor has an order parameter symmetry, which spontaneously breaks the crystalline symmetry in its superconducting state. This state can be observed, for example, by thermodynamic or upper critical field experiments in which a magnetic field is rotated with respect to the crystalline axes. The corresponding physical quantity then directly reflects the symmetry of the order parameter. We present a study on the superconducting upper critical field of the Nb-doped topological insulator NbxBi2Se3 for various magnetic field orientations parallel and perpendicular to the basal plane of the Bi2Se3 layers. The ...


Electronic Fingerprints Of Cr And V Dopants In The Topological Insulator Sb₂Te₃, Wenhan Zhang, Damien West, Seng Huat Lee, Yunsheng Qiu, Cui-Zu Chang, Jagadeesh S. Moodera, Yew San Hor, Shengbai Zhang, Weida Wu Oct 2018

Electronic Fingerprints Of Cr And V Dopants In The Topological Insulator Sb₂Te₃, Wenhan Zhang, Damien West, Seng Huat Lee, Yunsheng Qiu, Cui-Zu Chang, Jagadeesh S. Moodera, Yew San Hor, Shengbai Zhang, Weida Wu

Yew San Hor

By combining scanning tunneling microscopy/spectroscopy and first-principles calculations, we systematically study the local electronic states of magnetic dopants V and Cr in the topological insulator (TI) Sb2Te3. Spectroscopic imaging shows diverse local defect states between Cr and V, which agree with our first-principle calculations. The unique spectroscopic features of V and Cr dopants provide electronic fingerprints for the codoped magnetic TI samples with the enhanced quantum anomalous Hall effect. Our results also facilitate the exploration of the underlying mechanism of the enhanced quantum anomalous Hall temperature in Cr/V codoped TIs.


Gas Pressure Dependence Of Microwave Pulses Generated By Laser-Produced Filament Plasmas, Alexander Englesbe, Jennifer Elle, Remington Reid, Adrian Lucero, Hugh Pohle, Matthew Domonkos, Serge Y. Kalmykov, Karl Krushelnick, Andreas Schmitt-Sody Oct 2018

Gas Pressure Dependence Of Microwave Pulses Generated By Laser-Produced Filament Plasmas, Alexander Englesbe, Jennifer Elle, Remington Reid, Adrian Lucero, Hugh Pohle, Matthew Domonkos, Serge Y. Kalmykov, Karl Krushelnick, Andreas Schmitt-Sody

Serge Youri Kalmykov

The plasma arising due to the propagation of a filamenting ultrafast laser pulse in air contains currents driven by the pulse that generate radiated electromagnetic fields. We report absolutely calibrated measurements of the frequency spectrum of microwaves radiated by the filament plasma from 2–40 GHz. The emission pattern of the electric field spectrum is mapped as a function of air pressure from atmosphere to 0.5 Torr. For fixed laser pulse energy, duration, and focal geometry, we observe that decreasing the air pressure by a factor of approximately 103 increases the amplitude of the electric field waveform by a ...


Local Environment Of Iron And Uranium Ions In Vitrified Iron Phosphate Glasses Studied By Fe K And Uliii-Edge X-Ray Absorption Fine Structure Spectroscopy, Mevlüt Karabulut, G. K. Marasinghe, C. S. Ray, D. E. Day, George Daniel Waddill, P. G. Allen, C. H. Booth, J. J. Bucher, D. L. Caulder, D. K. Shuh, M. Grimsditch, M.-L. Saboungi Sep 2018

Local Environment Of Iron And Uranium Ions In Vitrified Iron Phosphate Glasses Studied By Fe K And Uliii-Edge X-Ray Absorption Fine Structure Spectroscopy, Mevlüt Karabulut, G. K. Marasinghe, C. S. Ray, D. E. Day, George Daniel Waddill, P. G. Allen, C. H. Booth, J. J. Bucher, D. L. Caulder, D. K. Shuh, M. Grimsditch, M.-L. Saboungi

Delbert E. Day

The local structure of iron and uranium ions in a series of iron phosphate glasses with the general composition (40 - x)Fe2O3-xUO2-60P2O5 and (1-x-y)(40Fe2O3-60P2O5)-xUO2-y(Na2O or CaO) was investigated using Fe K-edge and U LIII-edge x-ray absorption fine structure spectroscopy. Replacing Fe2O3 by UO2 in the glass caused more distortion in the coordination environment of Fe(III) ions. Extended x-ray absorption fine structure fits revealed that the Fe-P bonds observed in the base ...


A High Energy X-Ray And Neutron Scattering Study Of Iron Phosphate Glasses Containing Uranium, Mevlüt Karabulut, G. K. Marasinghe, C. S. Ray, Y. S. Badyal, M.-L. Saboungi, S. Shastri, D. Haeffner, George Daniel Waddill, D. E. Day Sep 2018

A High Energy X-Ray And Neutron Scattering Study Of Iron Phosphate Glasses Containing Uranium, Mevlüt Karabulut, G. K. Marasinghe, C. S. Ray, Y. S. Badyal, M.-L. Saboungi, S. Shastri, D. Haeffner, George Daniel Waddill, D. E. Day

Delbert E. Day

The atomic structure of iron phosphate glasses containing uranium has been studied by complementary neutron and x-ray scattering techniques. by combining x-ray and neutron structure factors, detailed information about different pair interactions has been obtained. Most of the basic structural features such as coordination numbers and O-O and P-O distances in uranium containing glasses are the same as those in the base glass of batch composition 40Fe2O3-60P2O5 (mol %). However, the Fe-O distances change slightly with the addition of uranium. The observed structural parameters support a structural model in which the waste elements occupy voids in the Fe-O-P network, hence, not ...


Tailoring The Asymmetric Magnetoimpedance Response In Exchange-Biased Ni - Fe Multilayers, Ufuk Kilic, Carolina Ross, Carlos Garcia Sep 2018

Tailoring The Asymmetric Magnetoimpedance Response In Exchange-Biased Ni - Fe Multilayers, Ufuk Kilic, Carolina Ross, Carlos Garcia

Ufuk Kilic

The dependence of the asymmetric magnetoimpedance (MI) response on the directions of both the magnetic field and the exchange bias is studied for an [NiFe(60nm)/IrMn(35nm)]×5 multilayer system. The antiferromagnetic (AFM) layers create an exchange bias that shifts both the hysteresis loop and the MI response of NiFe; the strength of this coupling depends on the thicknesses of both the ferromagnetic layer and the AFM layer. Tuning the exchange-bias angle and the applied-magnetic-field direction provides a practical method to control the symmetry and the magnitude of the MI response. The observed asymmetric response can ...


Solid Deuterium Surface Degradation At Ultracold Neutron Sources, Alexander Anghel, Thomas L. Bailey, George Bison, Bertrand Blau, Leah J. Broussard, Stephen M. Clayton, Christopher Cude-Woods, Manfred Daum, Ayman I. Hawari, Nora Hild, Paul R. Huffman, Takeyasu M. Ito, Klaus Kirch, E. Korobkina, Bernhard Lauss, Kent Leung, E. M. Lutz, Mark Makela, G. Medlin, C. L. Morris, Robert W. Pattie, Dieter Ries, Alexander Saunders, Phillip Schmidt-Wellenburg, Vadim Talanov, Albert R. Young, Bernard Wehring, C. White, Michael Wohlmuther, Geza Zsigmond Aug 2018

Solid Deuterium Surface Degradation At Ultracold Neutron Sources, Alexander Anghel, Thomas L. Bailey, George Bison, Bertrand Blau, Leah J. Broussard, Stephen M. Clayton, Christopher Cude-Woods, Manfred Daum, Ayman I. Hawari, Nora Hild, Paul R. Huffman, Takeyasu M. Ito, Klaus Kirch, E. Korobkina, Bernhard Lauss, Kent Leung, E. M. Lutz, Mark Makela, G. Medlin, C. L. Morris, Robert W. Pattie, Dieter Ries, Alexander Saunders, Phillip Schmidt-Wellenburg, Vadim Talanov, Albert R. Young, Bernard Wehring, C. White, Michael Wohlmuther, Geza Zsigmond

Robert W. Pattie Jr.

Solid deuterium (sD  is used as an efficient converter to produce ultracold neutrons (UCN). It is known that the sD must be sufficiently cold, of high purity and mostly in its ortho-state in order to guarantee long lifetimes of UCN in the solid from which they are extracted into vacuum. Also the UCN transparency of the bulk sD  material must be high because crystal inhomogeneities limit the mean free path for elastic scattering and reduce the extraction efficiency. Observations at the UCN sources at Paul Scherrer Institute and at Los Alamos National Laboratory consistently show a decrease of the UCN ...


Temperaments And Learning Styles Vs. Academic Performance Of First-Semester Physics Students, Shel Randall Jul 2018

Temperaments And Learning Styles Vs. Academic Performance Of First-Semester Physics Students, Shel Randall

Shel Randall

Purpose: The purpose of this retrospective quantitative correlational study was to determine the relationship of student temperament (as measured by the online Jung Typology Test) and learning styles (as measured by the Felder-Soloman Index of Learning Styles) to academic performance of first-semester physics students while enrolled in a Sierra Community College Physics Department course during the 2014 – 2016 school years
Methodology: This is a retrospective quantitative correlational study of the relationship between student personality information self-reported by survey and student performance as measured by semester grades. The historical survey data consists of results from two online assessments: the JTT (measuring ...