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Articles 31 - 60 of 152
Full-Text Articles in Physics
Permutation Entropy And Statistical Complexity Analysis Of Turbulence In Laboratory Plasmas And The Solar Wind, P. J. Weck, David A. Schaffner, M. R. Brown
Permutation Entropy And Statistical Complexity Analysis Of Turbulence In Laboratory Plasmas And The Solar Wind, P. J. Weck, David A. Schaffner, M. R. Brown
Physics Faculty Research and Scholarship
The Bandt-Pompe permutation entropy and the Jensen-Shannon statistical complexity are used to analyze fluctuating time series of three different turbulent plasmas: the magnetohydrodynamic (MHD) turbulence in the plasma wind tunnel of the Swarthmore Spheromak Experiment (SSX), drift-wave turbulence of ion saturation current fluctuations in the edge of the Large Plasma Device (LAPD), and fully developed turbulent magnetic fluctuations of the solar wind taken from the Wind spacecraft. The entropy and complexity values are presented as coordinates on the CH plane for comparison among the different plasma environments and other fluctuation models. The solar wind is found to have the highest …
Nonexponential 1h Spin-Lattice Relaxation And Methyl Group Rotation In Molecular Solids, Peter A. Beckmann
Nonexponential 1h Spin-Lattice Relaxation And Methyl Group Rotation In Molecular Solids, Peter A. Beckmann
Physics Faculty Research and Scholarship
We report a quantitative measure of the nonexponential 1H spin-lattice relaxation resulting from methyl group (CH3) rotation in six polycrystalline van der Waals solids. We briefly review the subject in general to put the report in context. We then summarize several significant issues to consider when reporting 1H or 19F spin-lattice relaxation measurements when the relaxation is resulting from the rotation of a CH3 or CF3 group in a molecular solid.
Quantum Interference In The Field Ionization Of Rydberg Atoms, Rachel Feynman, Jacob Hollingsworth, Michael Vennettilli, Tamas Budner, Ryan Zmiewski, Donald Fahey, Thomas J. Carroll, Michael W. Noel
Quantum Interference In The Field Ionization Of Rydberg Atoms, Rachel Feynman, Jacob Hollingsworth, Michael Vennettilli, Tamas Budner, Ryan Zmiewski, Donald Fahey, Thomas J. Carroll, Michael W. Noel
Physics Faculty Research and Scholarship
We excite ultracold rubidium atoms in a magneto-optical trap to a coherent superposition of the three |mj | sublevels of the 37d5/2 Rydberg state. After some delay, during which the relative phases of the superposition components can evolve, we apply an electric field pulse to ionize the Rydberg electron and send it to a detector. The electron traverses many avoided crossings in the Stark levels as it ionizes. The net effect of the transitions at these crossings is to mix the amplitudes of the initial superposition into the same final states at ionization. Similar to a Mach-Zehnder interferometer, the three …
Magnetohydrodynamic Turbulence: Observation And Experiment, M. R. Brown, David A. Schaffner, P. J. Weck
Magnetohydrodynamic Turbulence: Observation And Experiment, M. R. Brown, David A. Schaffner, P. J. Weck
Physics Faculty Research and Scholarship
We provide a tutorial on the paradigms and tools of magnetohydrodynamic (MHD) turbulence. The principal paradigm is that of a turbulent cascade from large scales to small, resulting in power law behavior for the frequency power spectrum for magnetic fluctuations EB(f) . We will describe five useful statistical tools for MHD turbulence in the time domain: the temporal autocorrelation function, the frequency power spectrum, the probability distribution function of temporal increments, the temporal structure function, and the permutation entropy. Each of these tools will be illustrated with an example taken from MHD fluctuations in the solar wind. A single dataset …
Methoxy And Methyl Group Rotation: Solid State Nmr 1h Spin-Lattice Relaxation, Electronic Structure Calculations, Xray Diffractometry, And Scanning Electron Microscopy, Peter A. Beckmann, Clelia W. Mallory, Frank B. Mallory, Arnold L. Rheingold, Xianlong Wang
Methoxy And Methyl Group Rotation: Solid State Nmr 1h Spin-Lattice Relaxation, Electronic Structure Calculations, Xray Diffractometry, And Scanning Electron Microscopy, Peter A. Beckmann, Clelia W. Mallory, Frank B. Mallory, Arnold L. Rheingold, Xianlong Wang
Physics Faculty Research and Scholarship
We report solid-state (1) H nuclear magnetic resonance (NMR) spin-lattice relaxation experiments, X-ray diffractometry, field-emission scanning electron microscopy, and both single-molecule and cluster ab initio electronic structure calculations on 1-methoxyphenanthrene (1) and 3-methoxyphenanthrene (2) to investigate the rotation of the methoxy groups and their constituent methyl groups. The electronic structure calculations and the (1) H NMR relaxation measurements can be used together to determine barriers for the rotation of a methoxy group and its constituent methyl group and to develop models for the two coupled motions.
Observation Of Turbulent Intermittency Scaling With Magnetic Helicity In An Mhd Plasma Wind Tunnel, David A. Schaffner, A. Wan, M. R. Brown
Observation Of Turbulent Intermittency Scaling With Magnetic Helicity In An Mhd Plasma Wind Tunnel, David A. Schaffner, A. Wan, M. R. Brown
Physics Faculty Research and Scholarship
The intermittency in turbulent magnetic field fluctuations has been observed to scale with the amount of magnetic helicity injected into a laboratory plasma. An unstable spheromak injected into the MHD wind tunnel of the Swarthmore Spheromak Experiment displays turbulent magnetic and plasma fluctuations as it relaxes into a Taylor state. The level of intermittency of this turbulence is determined by finding the flatness of the probability distribution function of increments for magnetic pickup coil fluctuations B_ðtÞ. The intermittency increases with the injected helicity, but spectral indices are unaffected by this variation. While evidence is provided which supports the hypothesis that …
Solid State 1 H Spin - Lattice Relaxation And Isolated - Molecule And Cluster Electronic Structure Calculations In Organic Molecular Solids: The Relationship Between Structure And Methyl Group And T - Butyl Group Rotation, Xianlong Wang, Frank B. Mallory, Clelia W. Mallory, Hosanna R. Odhner, Peter A. Beckmann
Solid State 1 H Spin - Lattice Relaxation And Isolated - Molecule And Cluster Electronic Structure Calculations In Organic Molecular Solids: The Relationship Between Structure And Methyl Group And T - Butyl Group Rotation, Xianlong Wang, Frank B. Mallory, Clelia W. Mallory, Hosanna R. Odhner, Peter A. Beckmann
Physics Faculty Research and Scholarship
We report ab initio density functional theory electronic structure calculations of rotational barriers for t-butyl groups and their constituent methyl groups both in the isolated molecules and in central molecules in clusters built from the X-ray structure in four t-butyl aromatic compounds. The X-ray structures have been reported previously. We also report and interpret the temperature dependence of the solid state 1H nuclear magnetic resonance spin-lattice relaxation rate at 8.50, 22.5, and 53.0 MHz in one of the four compounds. Such experiments for the other three have been reported previously. We compare the computed barriers for methyl group and t-butyl …
I-127 And Pb-207 Solid-State Nmr Spectroscopy And Nuclear Spin Relaxation In Lead Iodide: A Preliminary Study, R. E. Taylor, Peter A. Beckmann, Shi Bai, C. Dybowski
I-127 And Pb-207 Solid-State Nmr Spectroscopy And Nuclear Spin Relaxation In Lead Iodide: A Preliminary Study, R. E. Taylor, Peter A. Beckmann, Shi Bai, C. Dybowski
Physics Faculty Research and Scholarship
Lead iodide is a layered structure that experiences polytypism. The 2H polytype contains high rates of iodine vacancies but retains its stoichiometry. This characteristic feature makes it potentially useful for many practical applications. The hopping of iodine ions among vacancies is the dominant motion in the 2H polytype. We present a preliminary 127I and 207Pb solid-state nuclear magnetic resonance (NMR) spectroscopy and spin–lattice relaxation study of the 2H polytype below 400 K. We present reasonable models for the solid-state NMR results in terms of the effects of iodine hopping and lattice vibrations.
Double Resonance Spectroscopy Of The D1Πu+ And B''B-Bar 1Σu+ States Near The Third Dissociation Threshold Of H2, R. C. Ekey, A. E. Cordova, W. Duan, Alexander M. Chartrand, Elizabeth Mccormack
Double Resonance Spectroscopy Of The D1Πu+ And B''B-Bar 1Σu+ States Near The Third Dissociation Threshold Of H2, R. C. Ekey, A. E. Cordova, W. Duan, Alexander M. Chartrand, Elizabeth Mccormack
Physics Faculty Research and Scholarship
Double-resonance laser spectroscopy via the E, F 1Σg+, v' = 6, J' state was used to probe the energy region below the third dissociation limit of molecular hydrogen. Resonantly enhanced multi-photon ionization spectra were recorded by detecting ion production as a function of energy using a time-of-flight mass spectrometer. Energies and line widths for the v = 14–17 levels of the D1Πu+ state of H2 are reported and compared to experimental data obtained by using VUV synchrotron light excitation (Dickenson et al. 2010 J. Chem. Phys. 133 144317) and fully ab …
Room-Temperature Multiferroic Hexagonal Lufeo3 Films, Wenbin Wang, Jun Zhao, Wenbo Wang, Zheng Gai, Nina Balke, Miaofang Chi, Ho Nyung Lee, Wei Tian, Leyi Zhu, Xuemei Cheng, David J. Keavney, Jieyu Yi, Thomas Z. Ward, Paul C. Snijders, Hans M. Christen, Weida Wu, Jian Shen, Xiaoshan Xu
Room-Temperature Multiferroic Hexagonal Lufeo3 Films, Wenbin Wang, Jun Zhao, Wenbo Wang, Zheng Gai, Nina Balke, Miaofang Chi, Ho Nyung Lee, Wei Tian, Leyi Zhu, Xuemei Cheng, David J. Keavney, Jieyu Yi, Thomas Z. Ward, Paul C. Snijders, Hans M. Christen, Weida Wu, Jian Shen, Xiaoshan Xu
Physics Faculty Research and Scholarship
The crystal and magnetic structures of single-crystalline hexagonal LuFeO3 films have been studied using x-ray, electron, and neutron diffraction methods. The polar structure of these films are found to persist up to 1050 K; and the switchability of the polar behavior is observed at room temperature, indicating ferroelectricity. An antiferromagnetic order was shown to occur below 440 K, followed by a spin reorientation resulting in a weak ferromagnetic order below 130 K. This observation of coexisting multiple ferroic orders demonstrates that hexagonal LuFeO3 films are room-temperature multiferroics.
Tuning Vortex Confinement By Magnetic Domains In A Superconductor/Ferromagnet Bilayer, Marta Z. Cieplak, Z. Adamus, M. Kończykowski, L. Y. Zhu, Xuemei Cheng, C. L. Chien
Tuning Vortex Confinement By Magnetic Domains In A Superconductor/Ferromagnet Bilayer, Marta Z. Cieplak, Z. Adamus, M. Kończykowski, L. Y. Zhu, Xuemei Cheng, C. L. Chien
Physics Faculty Research and Scholarship
We use a line of miniature Hall sensors to study the effect of magnetic-domain-induced vortex confinement on the flux dynamics in a superconductor/ferromagnet bilayer. A single tunable bilayer is built of a ferromagnetic Co/Pt multilayer with perpendicular magnetic anisotropy and a superconducting Nb layer, with the insulating layer in-between to avoid the proximity effect. The magnetic-domain patterns of various geometries are reversibly predefined in the Co/Pt multilayer using the appropriate magnetization procedure. The magnetic-domain geometry strongly affects vortex dynamics, leading to geometry-dependent trapping of vortices at the sample edge, nonuniform flux penetration, and strongly nonuniform critical current density. With the …
Pt Magnetic Polarization On Y3Fe5O12 And Magnetotransport Characteristics, Y. M. Lu, Y. Choi, C. M. Ortega, Xuemei Cheng, J. W. Cai, S. Y. Huang, L. Sun, C. L. Chien
Pt Magnetic Polarization On Y3Fe5O12 And Magnetotransport Characteristics, Y. M. Lu, Y. Choi, C. M. Ortega, Xuemei Cheng, J. W. Cai, S. Y. Huang, L. Sun, C. L. Chien
Physics Faculty Research and Scholarship
Thin Pt films on an yttrium iron garnet (YIG=Y3Fe5O12) show ferromagneticlike transport properties, which may impact the functionality of Pt in spin current detection, but do not provide direct quantitative information on the Pt magnetization. We report magnetic x-ray magnetic circular dichroism measurements of YIG/Pt(1.5 nm) showing an average Pt moment of 0.054 μB at 300 K and 0.076 μB at 20 K. This observation indicates strong proximity effects and induced magnetic ordering in Pt on magnetic insulators and their contribution to the spin-related measurements should not be neglected. The transport characteristics …
Turbulence And Transport Suppression Scaling With Flow Shear On The Large Plasma Device, David A. Schaffner, T. A. Carter, G. D. Rossi, D. S. Guice, J. E. Maggs, S. Vincena, B. Friedman
Turbulence And Transport Suppression Scaling With Flow Shear On The Large Plasma Device, David A. Schaffner, T. A. Carter, G. D. Rossi, D. S. Guice, J. E. Maggs, S. Vincena, B. Friedman
Physics Faculty Research and Scholarship
Continuous control over azimuthal flow and shear in the edge of the Large Plasma Device (LAPD) [W. Gekelman et al., Rev. Sci. Instr. 62, 2875 (1991)] has been achieved using a biasable limiter. This flow control has allowed a careful study of the effect of flow shear on pressure-gradient-driven turbulence and particle transport in LAPD. The combination of externally controllable shear in a turbulent plasma along with the detailed spatial diagnostic capabilities on LAPD makes the experiment a useful testbed for validation of shear suppression models. Motivated by these models, power-law fits are made to the density and radial velocity …
Nonlinear Instability In Simulations Of Large Plasma Device Turbulence, B. Friedman, T. A. Carter, M. V. Umansky, David A. Schaffner, I. Joseph
Nonlinear Instability In Simulations Of Large Plasma Device Turbulence, B. Friedman, T. A. Carter, M. V. Umansky, David A. Schaffner, I. Joseph
Physics Faculty Research and Scholarship
Several simulations of turbulence in the Large Plasma Device (LAPD) [Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] are energetically analyzed and compared with each other and with the experiment. The simulations use the same model, but different axial boundary conditions. They employ either periodic, zero-value, zero-derivative, or sheath axial boundaries. The linear stability physics is different between the scenarios because the various boundary conditions allow the drift wave instability to access different axial structures, and the sheath boundary simulation contains a conducting wall mode instability which is just as unstable as the drift waves. Nevertheless, the turbulence in …
Dark Matter Time Projection Chamber: Recent R&D Results, James B. R. Battat, S. Ahlen, M. Chernicoff
Dark Matter Time Projection Chamber: Recent R&D Results, James B. R. Battat, S. Ahlen, M. Chernicoff
Physics Faculty Research and Scholarship
The Dark Matter Time Projection Chamber collaboration recently reported a dark matter limit obtained with a 10 liter time projection chamber filled with CF4 gas. The 10 liter detector was capable of 2D tracking (perpendicular to the drift direction) and 2D fiducialization, and only used information from two CCD cameras when identifying tracks and rejecting backgrounds. Since that time, the collaboration has explored the potential benefits of photomultiplier tube and electronic charge readout to achieve 3D tracking, and particle identification for background rejection. The latest results of this effort is described here.
Methyl Group Rotation, H-1 Spin-Lattice Relaxation In An Organic Solid, And The Analysis Of Nonexponential Relaxation, Peter A. Beckmann, Evan Schneider
Methyl Group Rotation, H-1 Spin-Lattice Relaxation In An Organic Solid, And The Analysis Of Nonexponential Relaxation, Peter A. Beckmann, Evan Schneider
Physics Faculty Research and Scholarship
We report 1H spin-lattice relaxation measurements in polycrystalline 4,4′-dimethoxybiphenyl at temperatures between 80 and 300 K at NMR frequencies of ω0/2π = 8.50, 22.5, and 53.0 MHz. The data are interpreted in terms of the simplest possible Bloch-Wangsness-Redfield methyl group hopping model. Different solid states are observed at low temperatures. The 1H spin-lattice relaxation is nonexponential at higher temperatures where a stretched-exponential function fits the data very well, but this approach is phenomenological and not amenable to theoretical interpretation. (We provide a brief literature review of the stretched-exponential function.) The Bloch-Wangsness-Redfield model applies …
Growth Diagram And Magnetic Properties Of Hexagonal Lufe2o4 Thin Films, Wenbin Wang, Zheng Gai, Miaofang Chi, Jason D. Fowlkes, Jieyu Yi, Leyi Zhu, Xuemei Cheng, David J. Keavney, Paul C. Snijders, Thomas Z. Ward, Jian Shen, Xiaoshan Xu
Growth Diagram And Magnetic Properties Of Hexagonal Lufe2o4 Thin Films, Wenbin Wang, Zheng Gai, Miaofang Chi, Jason D. Fowlkes, Jieyu Yi, Leyi Zhu, Xuemei Cheng, David J. Keavney, Paul C. Snijders, Thomas Z. Ward, Jian Shen, Xiaoshan Xu
Physics Faculty Research and Scholarship
A growth diagram of Lu-Fe-O compounds on MgO(111) substrates using pulsed laser deposition is constructed based on extensive growth experiments. The LuFe2O4 phase can only be grown in a small range of temperature and O2 pressure conditions. An understanding of the growth mechanism of Lu-Fe-O compound films is offered in terms of the thermochemistry at the surface. Superparamagnetism is observed in the LuFe2O4 film and is explained in terms of the effect of the impurity hexagonal LuFeO3 (h-LuFeO3) phase and structural defects.
Structure And Magnetotransport Properties Of Epitaxial Nanocomposite La0.67ca0.33mno3:Srtio3 Thin Films Grown By A Chemical Solution Approach, Ling Fei, Leyi Zhu, Xuemei Cheng, Haiyan Wang, Stacy M. Baber, Joshua Hill, Qianglu Lin, Yun Xu, Shuguang Deng, Hongmei Luo
Structure And Magnetotransport Properties Of Epitaxial Nanocomposite La0.67ca0.33mno3:Srtio3 Thin Films Grown By A Chemical Solution Approach, Ling Fei, Leyi Zhu, Xuemei Cheng, Haiyan Wang, Stacy M. Baber, Joshua Hill, Qianglu Lin, Yun Xu, Shuguang Deng, Hongmei Luo
Physics Faculty Research and Scholarship
Epitaxial La0.67Ca0.33MnO3:SrTiO3 (LCMO:STO) composite thin films have been grown on single crystal LaAlO3(001) substrates by a cost effective polymer-assisted deposition method. Both x-ray diffraction and high-resolution transmission electron microscopy confirm the growth of epitaxial films with an epitaxial relationship between the films and the substrates as (002)film||(002)sub and [202]film||[202]sub. The transport property measurement shows that the STO phase significantly increases the resistivity and enhances the magnetoresistance (MR) effect of LCMO and moves the metal-insulator transition to lower temperatures. For example, the MR values measured …
Crystal Field Splitting And Optical Bandgap Of Hexagonal Lufeo3 Films, Wenbin Wang, Hongwei Wang, Xiaoying Xu, Leyi Zhu, Lixin He, Elizabeth Wills, Xuemei Cheng, David J. Keavney, Jian Shen, Xifan Wu, Xiaoshan Xu
Crystal Field Splitting And Optical Bandgap Of Hexagonal Lufeo3 Films, Wenbin Wang, Hongwei Wang, Xiaoying Xu, Leyi Zhu, Lixin He, Elizabeth Wills, Xuemei Cheng, David J. Keavney, Jian Shen, Xifan Wu, Xiaoshan Xu
Physics Faculty Research and Scholarship
Hexagonal LuFeO3 films have been studied using x-ray absorption and optical spectroscopy. The crystal splitting of Fe3+ is extracted as Ee′−Ee″ = 0.7 eV and Ea1′−Ee′ = 0.9 eV, and a 2.0 eV optical bandgap is determined assuming a direct gap. First-principles calculations confirm the experiments that the relative energies of crystal field splitting states do follow Ea1′>Ee′>Ee″ with slightly underestimated values and a bandgap of 1.35 eV.
Modification Of Turbulent Transport With Continuous Variation Of Flow Shear In The Large Plasma Device, David A. Schaffner, T. A. Carter, G. D. Rossi, D. S. Guice, J. E. Maggs, S. Vincena, B. Friedman
Modification Of Turbulent Transport With Continuous Variation Of Flow Shear In The Large Plasma Device, David A. Schaffner, T. A. Carter, G. D. Rossi, D. S. Guice, J. E. Maggs, S. Vincena, B. Friedman
Physics Faculty Research and Scholarship
Continuous control over azimuthal flow and shear in the edge of the Large Plasma Device (LAPD) has been achieved using a biasable limiter which has allowed a careful study of the effect of flow shear on pressure-gradient-driven turbulence and transport in the LAPD. The LAPD rotates spontaneously in the ion diamagnetic direction; positive limiter bias first reduces, then minimizes (producing a near-zero shear state), and finally reverses the flow into the electron diamagnetic direction. Degradation of particle confinement is observed in the minimum shearing state and a reduction in the turbulent particle flux is observed with increasing shearing in both …
Sheared-Flow Induced Confinement Transition In A Linear Magnetized Plasma, S. Zhou, W. W. Heidbrink, H. Boehmer, R. Mcwilliams, T. A. Carter, S. Vincena, B. Friedman, David A. Schaffner
Sheared-Flow Induced Confinement Transition In A Linear Magnetized Plasma, S. Zhou, W. W. Heidbrink, H. Boehmer, R. Mcwilliams, T. A. Carter, S. Vincena, B. Friedman, David A. Schaffner
Physics Faculty Research and Scholarship
A magnetized plasma cylinder (12 cm in diameter) is induced by an annular shape obstacle at the Large Plasma Device [W. Gekelman, H. Pfister, Z. Lucky, J. Bamber, D. Leneman, and J. Maggs, Rev. Sci. Instrum. 62, 2875 (1991)]. Sheared azimuthal flow is driven at the edge of the plasma cylinder through edge biasing. Strong fluctuations of density and potential (δn/n~eδφ/kTe~0.5) are observed at the plasma edge, accompanied by a large density gradient (Ln=∣∣∇lnn∣∣−1~2cm) and shearing rate (γ~300kHz). Edge turbulence and cross-field transport are modified by changing the bias voltage (Vbias) on the obstacle and the axial magnetic field …
Energy Dynamics In A Simulation Of Lapd Turbulence, B. Friedman, T. A. Carter, M. V. Umansky, David A. Schaffner, B. Dudson
Energy Dynamics In A Simulation Of Lapd Turbulence, B. Friedman, T. A. Carter, M. V. Umansky, David A. Schaffner, B. Dudson
Physics Faculty Research and Scholarship
Energy dynamics calculations in a 3D fluid simulation of drift wave turbulence in the linear Large Plasma Device [W. Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] illuminate processes that drive and dissipate the turbulence. These calculations reveal that a nonlinear instability dominates the injection of energy into the turbulence by overtaking the linear drift wave instability that dominates when fluctuations about the equilibrium are small. The nonlinear instability drives flute- like (kk 1⁄4 0) density fluctuations using free energy from the background density gradient. Through nonlinear axial wavenumber transfer to kk 61⁄4 0 fluctuations, the nonlinear instability accesses …
Single-Crystal X-Ray Diffraction, Isolated-Molecule And Cluster Electronic Structure Calculations, And Scanning Electron Microscopy In An Organic Solid: Models For Intramolecular Motion In 4,4'-Dimethoxybiphenyl., Xianlong Wang, Loolita Rotkina, Hong Su, Peter A. Beckmann
Single-Crystal X-Ray Diffraction, Isolated-Molecule And Cluster Electronic Structure Calculations, And Scanning Electron Microscopy In An Organic Solid: Models For Intramolecular Motion In 4,4'-Dimethoxybiphenyl., Xianlong Wang, Loolita Rotkina, Hong Su, Peter A. Beckmann
Physics Faculty Research and Scholarship
This paper brings together field emission scanning electron microscopy, single-crystal X-ray diffraction, and density functional electronic structure calculations in both an isolated molecule and a cluster of seven whole and fourteen half molecules of 4,4′-dimethoxybiphenyl to investigate coupled methyl-group rotation (over a barrier) and methoxy-group libration (meaning a rotation from the ground state not all the way to the transition state and back again). The structure of the isolated molecule, determined by the electronic structure calculations, is compared with the structure of the molecule found in the crystal. As the methyl group rotates from its ground state to its transition …
Nonexponential Solid State 1h And 19f Spin–Lattice Relaxation, Single-Crystal X-Ray Diffraction, And Isolated-Molecule And Cluster Electronic Structure Calculations In An Organic Solid: Coupled Methyl Group Rotation And Methoxy Group Libration In 4,4′-Dimethoxyoctafluorobiphenyl, Donald P. Fahey, William G. Dougherty Jr, W. Scott Kassel, Xianlong Wang, Peter A. Beckmann
Nonexponential Solid State 1h And 19f Spin–Lattice Relaxation, Single-Crystal X-Ray Diffraction, And Isolated-Molecule And Cluster Electronic Structure Calculations In An Organic Solid: Coupled Methyl Group Rotation And Methoxy Group Libration In 4,4′-Dimethoxyoctafluorobiphenyl, Donald P. Fahey, William G. Dougherty Jr, W. Scott Kassel, Xianlong Wang, Peter A. Beckmann
Physics Faculty Research and Scholarship
We investigate the relationship between intramolecular rotational dynamics and molecular and crystal structure in 4,4′-dimethoxyoctafluorobiphenyl. The techniques are electronic structure calculations, X-ray diffractometry, and 1H and 19F solid state nuclear magnetic resonance relaxation. We compute and measure barriers for coupled methyl group rotation and methoxy group libration. We compare the structure and the structure-motion relationship in 4,4′-dimethoxyoctafluorobiphenyl with the structure and the structure-motion relationship in related compounds in order to observe trends concerning the competition between intramolecular and intermolecular interactions. The 1H spin–lattice relaxation is nonexponential in both the high-temperature short-correlation time limit and in the low-temperature long-correlation time limit, …
Dipole-Dipole Interaction Between Rubidium Rydberg Atoms, Emily Altiere, Donald Fahey, Michael Noel, Rachel J. Smith, Thomas J. Carroll
Dipole-Dipole Interaction Between Rubidium Rydberg Atoms, Emily Altiere, Donald Fahey, Michael Noel, Rachel J. Smith, Thomas J. Carroll
Physics Faculty Research and Scholarship
Ultracold Rydberg atoms in a static electric field can exchange energy via the dipole-dipole interaction. The Stark effect shifts the energy levels of the atoms which tunes the energy exchange into resonance at specific values of the electric field (Forster resonances). We excite rubidium atoms to Rydberg states by focusing either a 480 nm beam from a tunable dye laser or a pair of diode lasers into a magneto-optical trap. The trap lies at the center of a configuration of electrodes. We scan the electric field by controlling the voltage on the electrodes while measuring the fraction of atoms that …
Excitation Of Rydberg States In Rubidium With Near Infrared Diode Lasers, Donald Fahey, Michael Noel
Excitation Of Rydberg States In Rubidium With Near Infrared Diode Lasers, Donald Fahey, Michael Noel
Physics Faculty Research and Scholarship
A system of three external cavity diode lasers is used to excite Rydberg states in rubidium. The 5S -> 5P -> 5D transitions are driven using lasers with lambda = 780 and 776 nm respectively. From the 5D state, atoms fluoresce down to the 6P state. The final transition to Rydberg levels is from the 6P state with laser light near lambda = 1016 nm. The nS and nD Rydberg states are accessible directly and with the application of a modest electric field nP states can also be excited. As a test of this system, Stark spectra are collected for …
Spectroscopic Observation Of Bound Ungerade Ion-Pair States In Molecular Hydrogen, R. C. Ekey Jr., Elizabeth Mccormack
Spectroscopic Observation Of Bound Ungerade Ion-Pair States In Molecular Hydrogen, R. C. Ekey Jr., Elizabeth Mccormack
Physics Faculty Research and Scholarship
Frequency-resolved observations of heavy Rydberg states in molecular hydrogen are reported in the ungerade manifold of states. Double-resonance spectroscopy via the E, F (1) Sigma(+)(g), v' = 6 state has been used to probe the energy region above the H(1s) + H(3l) dissociation threshold. Resonances are observed by ionizing H(3l) to produce H(+), which is then detected by using a time-of-flight mass spectrometer. The kinetic energy of the H(+) ion confirms that the observed signal is due to the photoionization of neutral H(3l) atoms, indicating that dissociation is a significant decay channel for the ion-pair states. The pattern of energies …
First Dark Matter Search Results From A Surface Run Of The 10-L Dmtpc Directional Dark Matter Detector, S. Ahlen, James B. R. Battat, T. Caldwell, C. Deaconu, D. Dujmic, W. Fedus, P. Fisher, F. Golub, S. Henderson, A. Inglis, A. Kaboth, G. Kohse, R. Lanza, A. Lee, J. Lopez, J. Monroe, T. Sahin, G. Sciolla, N. Skvorodnev, H. Tomita, H. Wellenstein, I. Wolfe, R. Yamamoto, H. Yegoryan
First Dark Matter Search Results From A Surface Run Of The 10-L Dmtpc Directional Dark Matter Detector, S. Ahlen, James B. R. Battat, T. Caldwell, C. Deaconu, D. Dujmic, W. Fedus, P. Fisher, F. Golub, S. Henderson, A. Inglis, A. Kaboth, G. Kohse, R. Lanza, A. Lee, J. Lopez, J. Monroe, T. Sahin, G. Sciolla, N. Skvorodnev, H. Tomita, H. Wellenstein, I. Wolfe, R. Yamamoto, H. Yegoryan
Physics Faculty Research and Scholarship
The Dark Matter Time Projection Chamber (DMTPC) is a low pressure (75 Tort CF(4)) 10 liter detector capable of measuring the vector direction of nuclear recoils with the goal of directional dark matter detection. In this Letter we present the first dark matter limit from DMTPC from a surface run at MIT. In an analysis window of 80-200 keV recoil energy, based on a 35.7 g-day exposure, we set a 90% C.L. upper limit on the spin-dependent WIMP-proton cross section of 2.0 x 10(-33) cm(2) for 115 GeV/c(2) dark matter particle mass.
Intramolecular And Intermolecular Contributions To The Barriers For Rotation Of Methyl Groups In Crystalline Solids: Electronic Structure Calculations And Solid State Nmr Relaxation Measurements, Xianlong Wang, Peter A. Beckmann, Clelia W. Mallory, Arnold L. Rheingold, Antonio G. Pasquale, Patrick L. Carroll, Frank B. Mallory
Intramolecular And Intermolecular Contributions To The Barriers For Rotation Of Methyl Groups In Crystalline Solids: Electronic Structure Calculations And Solid State Nmr Relaxation Measurements, Xianlong Wang, Peter A. Beckmann, Clelia W. Mallory, Arnold L. Rheingold, Antonio G. Pasquale, Patrick L. Carroll, Frank B. Mallory
Physics Faculty Research and Scholarship
The rotation barriers for 10 different methyl groups in five methyl-substituted phenanthrenes and three methyl-substituted naphthalenes were determined by ab initio electronic structure calculations, both for the isolated molecules and for the central molecules in clusters containing 8–13 molecules. These clusters were constructed computationally using the carbon positions obtained from the crystal structures of the eight compounds and the hydrogen positions obtained from electronic structure calculations. The calculated methyl rotation barriers in the clusters (Eclust) range from 0.6 to 3.4 kcal/mol. Solid-state 1H NMR spin–lattice relaxation rate measurements on the polycrystalline solids gave experimental activation energies (ENMR) for methyl rotation …
The Case For A Directional Dark Matter Detector And The Status Of Current Experimental Efforts, S. Ahlen, N. Afshordi, James B. R. Battat, J. Billard, N. Bozorgnia, S. Burgos, T. Caldwell, J. M. Carmona, S. Cebrian, P. Colas, T. Dafni, E. Daw, D. Dujmic, A. Dushkin, W. Fedus, E. Ferrer, D. Finkbeiner, P. H. Fisher, J. Forbes, T. Fusayasu, J. Galan, T. Gamble, C. Ghag, I. Giomataris, M. Gold, H. Gomez, M. E. Gomez, P. Gondolo, A. Green, C. Grignon, O. Guillaudin, C. Hagemann, K. Hattori, S. Henderson, N. Higashi, C. Ida, F. J. Iguaz, A. Inglis, I. G. Irastorza, S. Iwaki, A. Kaboth, S. Kabuki, J. Kadyk, N. Kallivayalil, H. Kubo, S. Kurosawa, V. A. Kudryavtsev, T. Lamy, R. Lanza, T. B. Lawson, A. Lee, E. R. Lee, T. Lin, D. Loomba, J. Lopez, G. Luzon, T. Manobu, J. Martoff, F. Mayet, B. Mccluskey, E. Miller, K. Miuchi, J. Monroe, B. Morgan, D. Muna, A. St. J. Murphy, T. Naka, K. Nakamura, M. Nakamura, T. Nakano, G. G. Nicklin, H. Nishimura, K. Niwa, S. M. Paling, J. Parker, A. Petkov, M. Pipe, K. Pushkin, M. Robinson, A. Rodriguez, J. Rodriguez-Quintero, T. Sahin, R. Sanderson, N. Sanghi, D. Santos, O. Sato, T. Sawano, G. Sciolla, H. Sekiya, T. R. Slatyer, D. P. Snowden-Ifft, N. J. C. Spooner, A. Sugiyama, A. Takada, M. Takahashi, A. Takeda, T. Tanimori, K. Taniue, A. Tomas, H. Tomita, K. Tsuchiya, J. Turk, E. Tziaferi, K. Ueno, S. Vahsen, R. Vanderspek, J. Vergados, J. A. Villar, H. Wellenstein, I. Wolfe, R. K. Yamamoto, H. Yegoryan
The Case For A Directional Dark Matter Detector And The Status Of Current Experimental Efforts, S. Ahlen, N. Afshordi, James B. R. Battat, J. Billard, N. Bozorgnia, S. Burgos, T. Caldwell, J. M. Carmona, S. Cebrian, P. Colas, T. Dafni, E. Daw, D. Dujmic, A. Dushkin, W. Fedus, E. Ferrer, D. Finkbeiner, P. H. Fisher, J. Forbes, T. Fusayasu, J. Galan, T. Gamble, C. Ghag, I. Giomataris, M. Gold, H. Gomez, M. E. Gomez, P. Gondolo, A. Green, C. Grignon, O. Guillaudin, C. Hagemann, K. Hattori, S. Henderson, N. Higashi, C. Ida, F. J. Iguaz, A. Inglis, I. G. Irastorza, S. Iwaki, A. Kaboth, S. Kabuki, J. Kadyk, N. Kallivayalil, H. Kubo, S. Kurosawa, V. A. Kudryavtsev, T. Lamy, R. Lanza, T. B. Lawson, A. Lee, E. R. Lee, T. Lin, D. Loomba, J. Lopez, G. Luzon, T. Manobu, J. Martoff, F. Mayet, B. Mccluskey, E. Miller, K. Miuchi, J. Monroe, B. Morgan, D. Muna, A. St. J. Murphy, T. Naka, K. Nakamura, M. Nakamura, T. Nakano, G. G. Nicklin, H. Nishimura, K. Niwa, S. M. Paling, J. Parker, A. Petkov, M. Pipe, K. Pushkin, M. Robinson, A. Rodriguez, J. Rodriguez-Quintero, T. Sahin, R. Sanderson, N. Sanghi, D. Santos, O. Sato, T. Sawano, G. Sciolla, H. Sekiya, T. R. Slatyer, D. P. Snowden-Ifft, N. J. C. Spooner, A. Sugiyama, A. Takada, M. Takahashi, A. Takeda, T. Tanimori, K. Taniue, A. Tomas, H. Tomita, K. Tsuchiya, J. Turk, E. Tziaferi, K. Ueno, S. Vahsen, R. Vanderspek, J. Vergados, J. A. Villar, H. Wellenstein, I. Wolfe, R. K. Yamamoto, H. Yegoryan
Physics Faculty Research and Scholarship
We present the case for a dark matter detector with directional sensitivity. This document was developed at the 2009 CYGNUS workshop on directional dark matter detection, and contains contributions from theorists and experimental groups in the field. We describe the need for a dark matter detector with directional sensitivity; each directional dark matter experiment presents their project's status; and we close with a feasibility study for scaling up to a one ton directional detector, which would cost around $150M.