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Articles 1 - 30 of 46
Full-Text Articles in Physics
High-Temperature Calcium Vapor Cell For Spectroscopy On The 4s2 1s0-4s4p 3p1 Intercombination Line, Christopher J. Erickson, Brian Neyenhuis, Dallin S. Durfee
High-Temperature Calcium Vapor Cell For Spectroscopy On The 4s2 1s0-4s4p 3p1 Intercombination Line, Christopher J. Erickson, Brian Neyenhuis, Dallin S. Durfee
Faculty Publications
We have demonstrated a high-temperature vapor cell for absorption spectroscopy on the Ca intercombination line. The cell uses a dual-chamber design to achieve the high temperatures necessary for an optically dense vapor while avoiding the necessity of high-temperature vacuum valves and glass-to-metal seals. We have observed over 50% absorption in a single pass through the cell. Although pressure broadening in the cell prevented us from performing saturated-absorption spectroscopy, the broadening resulted in higher signal-to-noise ratios by allowing us to probe the atoms with intensities much greater than the 0.2µW/cm2 saturation intensity of the unbroadened transition. The techniques presented in this …
Nonmetal Ordering In Tic1-Xnx: Ground-State Structure And The Effects Of Finite Temperature, Gus L. W. Hart, Brian Kolb
Nonmetal Ordering In Tic1-Xnx: Ground-State Structure And The Effects Of Finite Temperature, Gus L. W. Hart, Brian Kolb
Faculty Publications
The TiC1-xNx system has long been prized in industry because of its desirable thermodynamic and hardness characteristics. Previous studies have not produced comprehensive results describing the ordering tendencies of TiC1-xNx at any temperature. We apply the mixed-basis cluster expansion and Monte Carlo methods to the problem and find a fascinating array of ground-state structures occurring at precise nitrogen-concentration intervals of ∆x=1/16 and related to each other by simple (201) quasisuperlattice motifs. Thermodynamic Monte Carlo results indicate that the critical ordering temperatures at all concentrations are well below room temperature. short-range ordering develops at T ≈ 800 K and exhibits the …
Ultracold Neutral Plasma Expansion In Two Dimensions, E. A. Cummings, J. E. Daily, Dallin S. Durfee, Scott D. Bergeson
Ultracold Neutral Plasma Expansion In Two Dimensions, E. A. Cummings, J. E. Daily, Dallin S. Durfee, Scott D. Bergeson
Faculty Publications
An isothermal model of ultracold neutral plasma expansion is extended to systems without spherical symmetry. It is used to interpret new fluorescence measurements on ultracold neutral calcium plasmas. For a self-similar expansion, the fluid equations are solved both analytically and numerically. The density and velocity solutions are used to predict fluorescence signals induced by a laser beam weakly focused into the plasma. Despite the simplicity of the model, predicted fluorescence signals reproduce major features of the experimental data
Multivalued Logic, Neutrosophy And Schrodinger Equation, Florentin Smarandache, Victor Christianto
Multivalued Logic, Neutrosophy And Schrodinger Equation, Florentin Smarandache, Victor Christianto
Branch Mathematics and Statistics Faculty and Staff Publications
This book was intended to discuss some paradoxes in Quantum Mechanics from the viewpoint of Multi-Valued-logic pioneered by Lukasiewicz, and a recent concept Neutrosophic Logic. Essentially, this new concept offers new insights on the idea of ‘identity’, which too often it has been accepted as given. Neutrosophy itself was developed in attempt to generalize Fuzzy-Logic introduced by L. Zadeh. While some aspects of theoretical foundations of logic are discussed, this book is not intended solely for pure mathematicians, but instead for physicists in the hope that some of ideas presented herein will be found useful. The book is motivated by …
Fluorescence Measurements Of Expanding Strongly Coupled Neutral Plasmas, E. A. Cummings, J. E. Daily, Dallin S. Durfee, Scott D. Bergeson
Fluorescence Measurements Of Expanding Strongly Coupled Neutral Plasmas, E. A. Cummings, J. E. Daily, Dallin S. Durfee, Scott D. Bergeson
Faculty Publications
We report new detailed density profile measurements in expanding strongly coupled neutral calcium plasmas. Using laser-induced fluorescence techniques, we determine plasma densities in the range of 10^5 to 10^9 cm^-3 with a time resolution limit as small as 7 ns. Strong coupling in the plasma ions is inferred directly from the fluorescence signals. Evidence for strong coupling at late times is presented, confirming a recent theoretical result.
Pumping Or Mixing System Using A Levitating Magnetic Element, Aexandre N. Terentiev
Pumping Or Mixing System Using A Levitating Magnetic Element, Aexandre N. Terentiev
Physics and Astronomy Faculty Patents
A system capable of pumping or mixing fluids using a rotating magnetic element or bearing levitated by a cold superconducting element is disclosed.
The H Ii Region/Pdr Connection: Self-Consistent Calculations Of Physical Conditions In Star-Forming Regions, Nicholas Paul Abel, Gary J. Ferland, G. Shaw, Peter A. M. Van Hoof
The H Ii Region/Pdr Connection: Self-Consistent Calculations Of Physical Conditions In Star-Forming Regions, Nicholas Paul Abel, Gary J. Ferland, G. Shaw, Peter A. M. Van Hoof
Physics and Astronomy Faculty Publications
We have performed a series of calculations designed to reproduce infrared diagnostics used to determine physical conditions in star-forming regions. We self-consistently calculate the thermal and chemical structure of an H II region and photodissociation region (PDR) that are in pressure equilibrium. This differs from previous work, which used separate calculations for each gas phase. Our calculations span a wide range of stellar temperatures, gas densities, and ionization parameters. We describe improvements made to the spectral synthesis code Cloudy that made these calculations possible. These include the addition of a molecular network with ~1000 reactions involving 68 molecular species and …
Using Genetic Algorithms To Map First-Principles Results To Model Hamiltonians: Application To The Generalized Ising Model For Alloys, Gus L. W. Hart, Volker Blum, Michael J. Walorski, Alex Zunger
Using Genetic Algorithms To Map First-Principles Results To Model Hamiltonians: Application To The Generalized Ising Model For Alloys, Gus L. W. Hart, Volker Blum, Michael J. Walorski, Alex Zunger
Faculty Publications
The cluster expansion method provides a standard framework to map first-principles generated energies for a few selected configurations of a binary alloy onto a finite set of pair and many-body interactions between the alloyed elements. These interactions describe the energetics of all possible configurations of the same alloy, which can hence be readily used to identify ground state structures and, through statistical mechanics solutions, find finite-temperature properties. In practice, the biggest challenge is to identify the types of interactions which are most important for a given alloy out of the many possibilities. We describe a genetic algorithm which automates this …
Numerical Integration Of The Teukolsky Equation In The Time Domain, Enrique Pazos-Avalos, Carlos O. Lousto
Numerical Integration Of The Teukolsky Equation In The Time Domain, Enrique Pazos-Avalos, Carlos O. Lousto
Physics and Astronomy Faculty Publications and Presentations
We present a fourth-order convergent, (2+1)-dimensional, numerical formalism to solve the Teukolsky equation in the time domain. Our approach is first to rewrite the Teukolsky equation as a system of first-order differential equations. In this way we get a system that has the form of an advection equation. This is then used in combination with a series expansion of the solution in powers of time. To obtain a fourth-order scheme we kept terms up to fourth derivative in time and use the advectionlike system of differential equations to substitute the temporal derivatives by spatial derivatives. This scheme is applied to …
Integral Neutron Multiplicity Measurements From Cosmic Ray Interactions In Lead, Thomas E. Ward, Alexander A. Rimsky-Korsakov, Nikolai A. Kudryashev, Denis E. Beller
Integral Neutron Multiplicity Measurements From Cosmic Ray Interactions In Lead, Thomas E. Ward, Alexander A. Rimsky-Korsakov, Nikolai A. Kudryashev, Denis E. Beller
Transmutation Sciences Physics (TRP)
Sixty element 3He neutron multiplicity detector systems were designed, constructed and tested for use in cosmic ray experiments with a 30-cm cube lead target. A series of measurements were performed for the cosmic ray configuration at ground level (3 meters water equivalent, mwe), in the St. Petersburg metro tunnel (185 mwe), and in the Pyhäsalmi mine in Finland (583 and 1185 mwe). Anomalous coincidence events with charged cosmic ray particles at sea level produced events with 100-120 neutrons due possibly to the total disintegration of the Pb nucleus. These events were also detected at 185 mwe, but the particles …
Direct Enumeration Of Alloy Configurations For Electronic Structural Properties, Gus L. W. Hart, Peter A. Graf, Kwiseon Kim, Wesley B. Jones
Direct Enumeration Of Alloy Configurations For Electronic Structural Properties, Gus L. W. Hart, Peter A. Graf, Kwiseon Kim, Wesley B. Jones
Faculty Publications
We present and apply an approach to directly enumerate the band gaps and effective masses of all possible zinc blende-based alloy configurations whose unit cell contains up to a specified number of atoms. This method allows us to map the space of band gaps and effective masses versus alloy composition and atomic configuration. We demonstrate that a large number of band gaps and effective masses are available. We also discuss convergence of the method with respect to unit cell size and the combined optimization of band gap and effective mass for AlGaAs and GaInP semiconductor alloys.
Cross Sections Fall 2005, Department Of Physics And Astronomy
Cross Sections Fall 2005, Department Of Physics And Astronomy
Cross Sections
No abstract provided.
J-Resolved He I Emission Predictions In The Low-Density Limit, R. P. Bauman, R. L. Porter, Gary J. Ferland, K. B. Macadam
J-Resolved He I Emission Predictions In The Low-Density Limit, R. P. Bauman, R. L. Porter, Gary J. Ferland, K. B. Macadam
Physics and Astronomy Faculty Publications
Determinations of the primordial helium abundance are used in precision cosmological tests. These require highly accurate He I recombination rate coefficients. Here we reconsider the formation of He I recombination lines in the low-density limit. This is the simplest case, and it forms the basis for the more complex situation in which collisions are important. The formation of a recombination line is a two-step process, beginning with the capture of a continuum electron into a bound state and followed by radiative cascade to ground. The rate coefficient for capture from the continuum is obtained from photoionization cross sections and detailed …
A Multi-Instrument Study Of The Helix Nebula Knots With The Hubble Space Telescope, C. R. O'Dell, W. J. Henney, Gary J. Ferland
A Multi-Instrument Study Of The Helix Nebula Knots With The Hubble Space Telescope, C. R. O'Dell, W. J. Henney, Gary J. Ferland
Physics and Astronomy Faculty Publications
We have conducted a combined observational and theoretical investigation of the ubiquitous knots in the Helix Nebula (NGC 7293). We have constructed a combined hydrodynamic + radiation model for the ionized portion of these knots and have accurately calculated a static model for their molecular regions. Imaging observations in optical emission lines were made with the Hubble Space Telescope's STIS, operating in a "slitless" mode, complemented by WFPC2 images in several of the same lines. The NICMOS camera was used to image the knots in H2. These observations, when combined with other studies of H2 and …
Dynamo Regimes With A Nonhelical Forcing, Pablo D. Mininni, Yannick Ponty, David C. Montgomery, Jean-Francois Pinton
Dynamo Regimes With A Nonhelical Forcing, Pablo D. Mininni, Yannick Ponty, David C. Montgomery, Jean-Francois Pinton
Dartmouth Scholarship
A three-dimensional numerical computation of magnetohydrodynamic dynamo behavior is described. The dynamo is mechanically forced with a driving term of the Taylor-Green type. The magnetic field development is followed from negligibly small levels to saturated values that occur at magnetic energies comparable to the kinetic energies. Although there is locally a nonzero helicity density, there is no overall integrated helicity in the system. Persistent oscillations are observed in the saturated state for not-too-large mechanical Reynolds numbers, oscillations in which the kinetic and magnetic energies vary out of phase but with no reversal of the magnetic field. The flow pattern exhibits …
Commutation Relations For Functions Of Operators, Mark K. Transtrum, Jean-Francois S. Van Huele
Commutation Relations For Functions Of Operators, Mark K. Transtrum, Jean-Francois S. Van Huele
Faculty Publications
We derive an expression for the commutator of functions of operators with constant commutations relations in terms of the partial derivatives of these functions. This result extends the well-known commutation relation between one operator and a function of another operator. We discuss the range of applicability of the formula with examples in quantum mechanics
Erratum: Computing The M = 1 Diocotron Frequency Via An Equilibrium Calculation In Non-Neutral Plasmas, Ross L. Spencer
Erratum: Computing The M = 1 Diocotron Frequency Via An Equilibrium Calculation In Non-Neutral Plasmas, Ross L. Spencer
Faculty Publications
Equation 14 in this paper contains errors.
Molecular Hydrogen In Star-Forming Regions: Implementation Of Its Microphysics In Cloudy, G. Shaw, Gary J. Ferland, N. P. Abel, P. C. Stancil, P. A. M. Van Hoof
Molecular Hydrogen In Star-Forming Regions: Implementation Of Its Microphysics In Cloudy, G. Shaw, Gary J. Ferland, N. P. Abel, P. C. Stancil, P. A. M. Van Hoof
Physics and Astronomy Faculty Publications
Much of the baryonic matter in the universe is in the form of H2, which includes most of the gas in Galactic and extragalactic interstellar clouds. Molecular hydrogen plays a significant role in establishing the thermal balance in many astrophysical environments and can be important as a spectral diagnostic of the gas. Modeling and interpretation of observations of such environments requires a quantitatively complete and accurate treatment of H2. Using this microphysical model of H2, we present illustrative calculations of prototypical astrophysical environments. This work forms the foundation for future investigations of these and …
The Effect Of Inharmonic Partials On Pitch Of Piano Tones, Brian E. Anderson, William J. Strong
The Effect Of Inharmonic Partials On Pitch Of Piano Tones, Brian E. Anderson, William J. Strong
Faculty Publications
Piano tones have partials whose frequencies are sharp relative to harmonic values. A listening test was conducted to determine the effect of inharmonicity on pitch for piano tones in the lowest three octaves of a piano. Nine real tones from the lowest three octaves of a piano were analyzed to obtain frequencies, relative amplitudes, and decay rates of their partials. Synthetic inharmonic tones were produced from these results. Synthetic harmonic tones, each with a twelfth of a semitone increase in the fundamental, were also produced. A jury of 21 listeners matched the pitch of each synthetic inharmonic tone to one …
Two-Photon Photoionization Of The Ca 4s3d^1d2 Level In An Optical Dipole Trap, E. A. Cummings, J. E. Daily, Dallin S. Durfee, Scott D. Bergeson, R. Gommers
Two-Photon Photoionization Of The Ca 4s3d^1d2 Level In An Optical Dipole Trap, E. A. Cummings, J. E. Daily, Dallin S. Durfee, Scott D. Bergeson, R. Gommers
Faculty Publications
We report an optical dipole trap for calcium. The trap is created by focusing a 488-nm argon-ion laser beam into a calcium magneto-optical trap. The argon-ion laser photoionizes atoms in the trap because of a near-resonance with the 4s4f 1^F3 level. By measuring the dipole-trap decay rate as a function of argon-ion laser intensity, we determine the 1^F3 photoionization cross section at our wavelength to be approximately 230 Mb.
Energy Levels And Transition Probabilities For Nitrogen-Like Fe Xx, V. Jonauskas, P. Bogdanovich, F. P. Keenan, M. E. Foord, R. F. Heeter, S. J. Rose, Gary J. Ferland, R. Kisielius, Peter A. M. Van Hoof, P. H. Norrington
Energy Levels And Transition Probabilities For Nitrogen-Like Fe Xx, V. Jonauskas, P. Bogdanovich, F. P. Keenan, M. E. Foord, R. F. Heeter, S. J. Rose, Gary J. Ferland, R. Kisielius, Peter A. M. Van Hoof, P. H. Norrington
Physics and Astronomy Faculty Publications
Energies of the 700 lowest levels in Fexx have been obtained using the multiconfiguration Dirac-Fock method. Configuration interaction method on the basis set of transformed radial orbitals with variable parameters taking into account relativistic corrections in the Breit-Pauli approximation was used to crosscheck our presented results. Transition probabilities, oscillator and line strengths are presented for electric dipole (E1), electric quadrupole (E2) and magnetic dipole (M1) transitions among these levels. The total radiative transition probabilities from each level are also provided. Results are compared with data compiled by NIST and with other theoretical work.
Cross Sections Spring 2005, Department Of Physics And Astronomy
Cross Sections Spring 2005, Department Of Physics And Astronomy
Cross Sections
No abstract provided.
Sound-Quality Analysis Of Sewing Machines (A), James Chatterley, Andrew Boone, Jonathan T. Blotter, Scott D. Sommerfeldt
Sound-Quality Analysis Of Sewing Machines (A), James Chatterley, Andrew Boone, Jonathan T. Blotter, Scott D. Sommerfeldt
Faculty Publications
Sound quality analysis procedure and results for six sewing machines ranging from entry level to professional grade will be presented. The procedure consisted of jury-based listening tests and quantification of sound quality using standard metrics. The procedures and analysis of the jury testing will be presented and discussed. The correlation between the quantitative metrics and the qualitative jury results will be presented. Sound localization scans, using near field acoustic holography techniques with accompanying results, performed in order to determine machine sound hot spots and possible sources for undesired sounds, will also be presented. Proposed modifications to machine structure in order …
Theoretical He I Emissivities In The Case B Approximation, R. L. Porter, R. P. Bauman, Gary J. Ferland, K. B. Macadam
Theoretical He I Emissivities In The Case B Approximation, R. L. Porter, R. P. Bauman, Gary J. Ferland, K. B. Macadam
Physics and Astronomy Faculty Publications
We calculate the He I case B recombination cascade spectrum using improved radiative and collisional data. We present new emissivities over a range of electron temperatures and densities. The differences between our results and the current standard are large enough to have a significant effect not only on the interpretation of observed spectra of a wide variety of objects, but also on determinations of the primordial helium abundance.
Self-Consistent Dynamic Models Of Steady Ionization Fronts. I. Weak-D And Weak-R Fronts, W. J. Henney, S. J. Arthur, R. J. R. Williams, Gary J. Ferland
Self-Consistent Dynamic Models Of Steady Ionization Fronts. I. Weak-D And Weak-R Fronts, W. J. Henney, S. J. Arthur, R. J. R. Williams, Gary J. Ferland
Physics and Astronomy Faculty Publications
We present a method for including steady state gas flows in the plasma physics code Cloudy, which was previously restricted to modeling static configurations. The numerical algorithms are described in detail, together with an example application to plane-parallel ionization-bounded H II regions. As well as providing the foundation for future applications to more complex flows, we find the following specific results regarding the effect of advection on ionization fronts in H II regions: (1) Significant direct effects of advection on the global emission properties occur only when the ionization parameter is lower than is typical for H II regions. For …
Optical Spectroscopy Of The Surface Population Of The Ρ Ophiuchi Molecular Cloud: The First Wave Of Star Formation, Bruce Wilking, Michael Meyer, John Robinson, Thomas Greene
Optical Spectroscopy Of The Surface Population Of The Ρ Ophiuchi Molecular Cloud: The First Wave Of Star Formation, Bruce Wilking, Michael Meyer, John Robinson, Thomas Greene
Physics Faculty Works
We present the results of optical spectroscopy of 139 stars obtained with the Hydra multiobject spectrograph. The objects extend over a 1.3 deg2 area surrounding the main cloud of the ρ Oph complex. The objects were selected from narrowband images to have Hα in emission. Using the presence of strong Hα emission, lithium absorption, location in the Hertzsprung-Russell diagram, or previously reported X-ray emission, we were able to identify 88 objects as young stars associated with the cloud. Strong Hα emission was confirmed in 39 objects with line widths consistent with their origin in magnetospheric accretion columns. Two of the …
The Vlt-Uves Survey For Molecular Hydrogen In High-Redshift Damped Lyman Α Systems: Physical Conditions In The Neutral Gas, Raghunathan Srianand, Patrick Petitjean, Cédric Ledoux, Gary J. Ferland, Gargi Shaw
The Vlt-Uves Survey For Molecular Hydrogen In High-Redshift Damped Lyman Α Systems: Physical Conditions In The Neutral Gas, Raghunathan Srianand, Patrick Petitjean, Cédric Ledoux, Gary J. Ferland, Gargi Shaw
Physics and Astronomy Faculty Publications
We study the physical conditions in damped Lyman α systems (DLAs), using a sample of 33 systems towards 26 quasi-stellar objects (QSOs) acquired for a recently completed survey of H2 by Ledoux, Petitjean & Srianand. We use the column densities of H2 in different rotational levels, together with those of C I, C I*, C I**, C II* and singly ionized atomic species to discuss the kinetic temperature, the density of hydrogen and the electronic density in the gas together with the ambient ultraviolet (UV) radiation field. Detailed comparisons are made between the observed properties in DLAs, the …
Anisotropic Thermal Expansion Of Monoclinic Potassium Lutetium Tungstate Single Crystals, Kunpeng Wang, Jianxiu Zhang, Jiyang Wang, Huaijin Zhang, Zhengping Wang, Wentao Yu, Xuping Wang, Qingming Lu, Mingfang Ba, Robert I. Boughton
Anisotropic Thermal Expansion Of Monoclinic Potassium Lutetium Tungstate Single Crystals, Kunpeng Wang, Jianxiu Zhang, Jiyang Wang, Huaijin Zhang, Zhengping Wang, Wentao Yu, Xuping Wang, Qingming Lu, Mingfang Ba, Robert I. Boughton
Physics and Astronomy Faculty Publications
The anisotropic thermal expansion of a single crystal of KLu WO4 2 KLuW , obtained by the top-seeded solution growth method, has been investigated over a wide temperature range 50– 600 °C . The linear thermal-expansion tensor has been determined and its principal X, Y, and Z axes are in the 705 , 010 , and 107 crystallographic directions, respectively. The principal thermal-expansion coefficients I, II, and III are 12.8 10−6, 7.8 10−6, and 22.2 10−6 K−1, respectively. The principal axis with maximum thermal expansion Z with III=22.2 10−6 is located at 10.37° from the c axis. In comparison with …
Thermal And Mechanical Properties Of Bawo4 Crystal, W. W. Ge, H. J. Wang, J. Y. Wang, J. H. Liu, X. G. Xu, X. B. Hu, M. H. Jiang, D. G. Ran, S. Q. Sun, H. R. Xia, Robert I. Boughton
Thermal And Mechanical Properties Of Bawo4 Crystal, W. W. Ge, H. J. Wang, J. Y. Wang, J. H. Liu, X. G. Xu, X. B. Hu, M. H. Jiang, D. G. Ran, S. Q. Sun, H. R. Xia, Robert I. Boughton
Physics and Astronomy Faculty Publications
A large single crystal of barium tungstate BaWO4 with dimensions of 22- mm diameter 80-mm length was grown by the Czochralski method using an iridium crucible. The melting point, molar enthalpy of fusion, and molar entropy of fusion of the crystal were determined to be 1775.10 K, 96 913.80 J mol−1, and 54.60 J K−1 mol−1, respectively. The average linear thermal-expansion coefficients are a=10.9526 10−6/K, b=10.8069 10−6 /K, and c =35.1063 10−6 /K in the temperature range from 303.15 to 1423.15 K along the three respective crystallographic axes. The density of the crystal follows an almost linear decrease from 6.393 …
Ion Cyclotron Waves In The Saturnian Magnetosphere Associated With Cassini's Engine Exhaust, C. T. Russell, J. S. Leisner, K. K. Khurana, M. K. Dougherty, X. Blanco-Cano, Jane L. Fox
Ion Cyclotron Waves In The Saturnian Magnetosphere Associated With Cassini's Engine Exhaust, C. T. Russell, J. S. Leisner, K. K. Khurana, M. K. Dougherty, X. Blanco-Cano, Jane L. Fox
Physics Faculty Publications
Five hours after the orbit insertion maneuver that placed Cassini into orbit about Saturn, a long (90 minute) burst of ion cyclotron waves were seen, very different than any waves on the inbound leg of the orbit or on succeeding orbits. The ion cyclotron waves were left-hand elliptically polarized and propagating at a moderately large angle to the local magnetic field. The waves had a noticeable compressional component consistent with their off angle propagation. The frequency band of the signals was moderately broad and consistent with the singly ionized components of the engine exhaust gases: CO2, N2 …