Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

Brigham Young University

Discipline
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 2581 - 2610 of 2906

Full-Text Articles in Physical Sciences and Mathematics

A Brief Introduction To Formal Methods, Paul E. Black, Kelly M. Hall, Michael D. Jones, Trent N. Larson, Phillip J. Windley May 1996

A Brief Introduction To Formal Methods, Paul E. Black, Kelly M. Hall, Michael D. Jones, Trent N. Larson, Phillip J. Windley

Faculty Publications

As hardware designs grow in size and complexity, current design methods are proving less adequate. Current methods for specification, design, and test are typically empirical or informal, that is, they are based on experience and argument. Formal methods are solidly based on mathematical logic systems and precise rules of inference. Formal methods offer a discipline which complements current methods so designers can successfully meet the demand for high performance systems. Formal methods covers a broad and diverse set of techniques aimed at improving computer correctness. This paper explains the role of specifications and implementation models in formal methods, and different …

Go to article

Simulations Of Electrostatic Modes Of Non-Neutral Plasmas With Small Aspect Ratio In A Penning Trap, Grant W. Mason, Ross L. Spencer, Jonathan A. Bennett May 1996

Simulations Of Electrostatic Modes Of Non-Neutral Plasmas With Small Aspect Ratio In A Penning Trap, Grant W. Mason, Ross L. Spencer, Jonathan A. Bennett

Faculty Publications

The dependence on induced charge, experimental geometry, and temperature of electrostatic modes in very low aspect ratio non-neutral plasmas in a Penning trap is considered. The modes are of interest as non-destructive diagnostics of the shape of the plasmas. These investigations include equilibrium calculations of plasma shapes and profiles at finite temperature and particle-in-cell simulations of axisymmetric modes. The results of the simulations are compared to the zero-temperature theory by Dubin [Phys. Rev. Lett. 66, 2076 (1991)] taken to first-order in the aspect ratio and to experimental measurements by Weimer et al. [Phys. Rev. A 49, 3842 (1994)]. In general, …

Go to article

Error Correction Via A Post-Processor For Continuous Speech Recognition, Eric K. Ringger, James F. Allen May 1996

Error Correction Via A Post-Processor For Continuous Speech Recognition, Eric K. Ringger, James F. Allen

Faculty Publications

This paper presents a new technique for overcoming several types of speech recognition errors by post-processing the output of a continuous speech recognizer. The post-processor output contains fewer errors, thereby making interpretation by higher-level modules, such as a parser, in a speech understanding system more reliable. The primary advantage to the post-processing approach over existing approaches for overcoming SR errors lies in its abilityto introduce options that are not available in the SR module’s output. This work provides evidence for the claim that a modern continuous speech recognizer can be used successfully in “black-box” fashion for robustly interpreting spontaneous utterances …

Go to article

Compressing Semi-Structured Text Using Hierarchical Phrase Identifications, Dan R. Olsen Jr., Craig G. Nevill-Manning, Ian H. Witten Apr 1996

Compressing Semi-Structured Text Using Hierarchical Phrase Identifications, Dan R. Olsen Jr., Craig G. Nevill-Manning, Ian H. Witten

Faculty Publications

The structure of this paper is as follows. We begin by identifying some characteristics of semi-structured text that have special relevance to data compression. We then give a brief account of a particular large textual database, and describe a compression scheme that exploits its structure. In addition to providing compression, the system gives some insight into the structure of the database. Finally we show how the hierarchical grammar can be generalized, first manually and then automatically, to yield further improvements in compression performance.

Go to article

Nature Among The Mormons: An Ecocritical Approach To Mormon Literature, Gail D. Ballard Jan 1996

Nature Among The Mormons: An Ecocritical Approach To Mormon Literature, Gail D. Ballard

Theses and Dissertations

Increasingly, environmentalists have focused on Judeo-Christian tradition as the cause of Western culture's ecological crisis. It is the purpose of this paper to examine the charges against Judeo-Christian tradition and to show how the revealed doctrines of The Church of Jesus Christ of Latter-day Saints provide possible solutions to environmental challenges. The resulting Latter-day Saint environmental paradigm will be superimposed on selected Mormon literature to determine how effectively the doctrines taught by Church authorities filtered into popular Mormon culture.

Despite the inspired teachings of Latter-day Saint prophets, Mormons remain unimpressive in their environmental practices. My research will show that while …

Go to article

High-Sensitivity Absorption Spectroscopy In Fe Ii, Scott D. Bergeson, K. L. Mullman, J. E. Lawler Jan 1996

High-Sensitivity Absorption Spectroscopy In Fe Ii, Scott D. Bergeson, K. L. Mullman, J. E. Lawler

Faculty Publications

We report the first measurements of UV oscillator strengths (ƒ-values) in Fe II from a high-sensitivity absorption experiment developed at the University of Wisconsin. The accuracy of our measurements is demonstrated by our reproducing well-known ƒ-value ratios in Fe I and Fe II. The first laboratory ƒ-value measurement of the 160.845 nm transition in Fe II is presented and compared to values in the literature. While this paper focuses on Fe II, the high-sensitivity absorption method that we have developed is applicable to essentially every element in the periodic table, for both neutral and ionized species, over a broad range …

Go to article

Branching Fractions And Oscillator Strengths For Fe Ii Transitions From The 3d6(5D)4p Subconfiguration, Scott D. Bergeson, K. L. Mullman, M. E. Wickliffe, J. E. Lawler Jan 1996

Branching Fractions And Oscillator Strengths For Fe Ii Transitions From The 3d6(5D)4p Subconfiguration, Scott D. Bergeson, K. L. Mullman, M. E. Wickliffe, J. E. Lawler

Faculty Publications

New experimental branching fractions and transition probabilities are reported for 56 transitions in Fe II. The branching fractions are measured with a Fourier transform spectrometer and also with a high-resolution grating spectrometer on a n optically thin hollow cathode discharge. Highly accurate experimental radiative lifetimes from the recent literature provide the normalization required to convert our branching fractions into absolute transition probabilities. Results are compared with experimental and theoretical values in the literature. Our new transition probabilities will establish the absolute scale for relative absorption oscillator strengths of vacuum ultraviolet lines measured using a new high-sensitivity absorption experiment at the …

Go to article

A New High Pressure Sapphire Nuclear Magnetic Resonance Cell, Shi Bai, Craig M. Taylor, Charles L. Mayne, Ronald J. Pugmire, David M. Grant Jan 1996

A New High Pressure Sapphire Nuclear Magnetic Resonance Cell, Shi Bai, Craig M. Taylor, Charles L. Mayne, Ronald J. Pugmire, David M. Grant

Faculty Publications

A new version of a single-crystal sapphire high pressure nuclear magnetic resonance (NMR) cell is described that is capable of controlling the sample pressure independent of the temperature. A movable piston inside the cell adjusts and controls the sample pressure from ambient conditions to 200 atm within plus or minus 0.3 atm. The linewidth at half-height for a 13C spectrum of carbon dioxide at 15degrees C and 57.8 atm is found to be 0.5 Hz. The carbon dioxide gas/liquid phase transition is clearly observed by measuring 13C chemical shifts as the sample pressure approaches equilibrium. The time required for this …

Go to article

Model Equations From Gyrokinetic Theory For A Non-Neutral Plasma To Include Temperature Effects And Applications To A Plasma Of Infinite Length, S. Neil Rasband Jan 1996

Model Equations From Gyrokinetic Theory For A Non-Neutral Plasma To Include Temperature Effects And Applications To A Plasma Of Infinite Length, S. Neil Rasband

Faculty Publications

Gyrokinetic equations are derived for applications to non-neutral plasmas in constant, straight magnetic fields wherein E X B drift velocities are of the same order as thermal velocities. The ratio of the E X B rotation frequency to the cyclotron frequency and the ratio of the gyroradius to a plasma scale length are assumed to be of order epsilon and terms are retained in the gyrokinetic expansion to second order to include finite-Larmor-radius (FLR) effects. A mode equation is obtained for a non-neutral plasma in the infinite-length approximation. The singularities of this equation are compared and contrasted with the familiar …

Go to article

Observation Of Beam-Induced Changes In The Polarization Of Balmer-Α Radiation Emitted Following Beam--Tilted-Foil Transmission, Wang Qi, David D. Allred, Larry V. Knight, Douglas L. Harper, Royal G. Albridge, Norman H. Tolk Dec 1995

Observation Of Beam-Induced Changes In The Polarization Of Balmer-Α Radiation Emitted Following Beam--Tilted-Foil Transmission, Wang Qi, David D. Allred, Larry V. Knight, Douglas L. Harper, Royal G. Albridge, Norman H. Tolk

Faculty Publications

Measurements of the circular polarization of Balmer-α radiation emitted by excited hydrogen atoms, following the transmission of (20-50)-keV protons through thin, tilted amorphous carbon foils, exhibit markedly unexpected behavior as a function of exposure of the foil to the proton beam. Specifically, the circular polarization changes from an initially well understood tilt-angle dependence to a behavior which, for low tilt angles, gives the opposite handedness of circular polarization from that predicted. In addition, the degree of alignment, indicated by the linear Stokes parameter M/I, is enhanced also as a function of dose. These changes in the tilt-angle dependence of the …

Go to article

A Provably Convergent Dynamic Training Method For Multi-Layer Perceptron Networks, Timothy L. Andersen, Tony R. Martinez Sep 1995

A Provably Convergent Dynamic Training Method For Multi-Layer Perceptron Networks, Timothy L. Andersen, Tony R. Martinez

Faculty Publications

This paper presents a new method for training multi-layer perceptron networks called DMP1 (Dynamic Multilayer Perceptron 1). The method is based upon a divide and conquer approach which builds networks in the form of binary trees, dynamically allocating nodes and layers as needed. The individual nodes of the network are trained using a genetic algorithm. The method is capable of handling real-valued inputs and a proof is given concerning its convergence properties of the basic model. Simulation results show that DMP1 performs favorably in comparison with other learning algorithms.

Go to article

An Integrated Framework For Learning And Reasoning, Christophe G. Giraud-Carrier, Tony R. Martinez Aug 1995

An Integrated Framework For Learning And Reasoning, Christophe G. Giraud-Carrier, Tony R. Martinez

Faculty Publications

Learning and reasoning are both aspects of what is considered to be intelligence. Their studies within AI have been separated historically, learning being the topic of machine learning and neural networks, and reasoning falling under classical (or symbolic) AI. However, learning and reasoning are in many ways interdependent. This paper discusses the nature of some of these interdependencies and proposes a general framework called FLARE, that combines inductive learning using prior knowledge together with reasoning in a propositional setting. Several examples that test the framework are presented, including classical induction, many important reasoning protocols and two simple expert systems.

Go to article

Surface Intersection Loop Destruction, Thomas W. Sederberg, Alan K. Zundel Jul 1995

Surface Intersection Loop Destruction, Thomas W. Sederberg, Alan K. Zundel

Faculty Publications

The intersection curve between two surface patches consists of one or more connected components or branches. Each component can be classified as either an open branch, with endpoints on at least one patch boundary, or as a closed loop.

Go to article

Numerical Calculation Of Axisymmetric Electrostatic Modes For Cold Finite-Length Non-Neutral Plasmas, Johnny K. Jennings, Ross L. Spencer, K. C. Hansen Jul 1995

Numerical Calculation Of Axisymmetric Electrostatic Modes For Cold Finite-Length Non-Neutral Plasmas, Johnny K. Jennings, Ross L. Spencer, K. C. Hansen

Faculty Publications

A numerical calculation of mode frequencies for cold, non-neutral plasmas is reported. The numerical method can be applied to any axisymmetric plasma shape in a trap. Here, it is used to study axisymmetric electrostatic modes in a long conducting cylinder. These modes were previously studied by Prasad and O'Neil [Phys. Fluids 26, 665 (1983)] and by Dubin [Phys. Rev. Lett. 66, 2076 (1991)]. In contrast to Dubin's calculation, the effects of a nearby cylindrical wall, including its influence on the shape of the plasma equilibrium, are considered. It is found that for plasmas with aspect ratios (length divided by diameter) …

Go to article

Hodographs And Normals Of Rational Curves And Surfaces, Thomas W. Sederberg, Takafumi Saito, Guo-Jin Wang Jun 1995

Hodographs And Normals Of Rational Curves And Surfaces, Thomas W. Sederberg, Takafumi Saito, Guo-Jin Wang

Faculty Publications

Derivatives and normals of rational Bézier curves and surface patches are discussed. A non-uniformly scaled hodograph of a degree m x n tensor-product rational surface, which provides correct derivative direction but not magnitude, can be written as a degree (2m - 2) x 2n or 2m x (2n - 2) vector function in polynomial Bézier form. Likewise, the scaled normal direction is degree (3m - 2) x(3n - 2). Efficient methods are developed for bounding these directions and the derivative magnitude.

Go to article

Using Multiple Statistical Prototypes To Classify Continuously Valued Data, Tony R. Martinez, Dan A. Ventura Jan 1995

Using Multiple Statistical Prototypes To Classify Continuously Valued Data, Tony R. Martinez, Dan A. Ventura

Faculty Publications

Multiple Statistical Prototypes (MSP) is a modification of a standard minimum distance classification scheme that generates muItiple prototypes per class using a modified greedy heuristic. Empirical comparison of MSP with other well-known learning algorithms shows MSP to be a robust algorithm that uses a very simple premise to produce good generalization and achieve parsimonious hypothesis representation.

Go to article

Waterjet Cutting Of Cross-Linked Glass, Fang Yuan, John A. Johnson, David D. Allred, Robert H. Todd Jan 1995

Waterjet Cutting Of Cross-Linked Glass, Fang Yuan, John A. Johnson, David D. Allred, Robert H. Todd

Faculty Publications

The cutting of cross-linked glasses such as silica and Corning 7059 can be difficult. We conducted an experimental study to determine the feasibility of using a high-speed waterjet to cut thin Corning 7095 glass. Cutting using either pure de-ionized high pressure water at 380 MPa (55 000 psi) or de-ionized water with entrained garnet abrasive was studied. The roughness of the cut surfaces was measured and compared. Photomicrographs were taken of glass examples cut at different traversing rates with pure water and with the abrasive entrained waterjet. Comparative studies of cutting with and without the entrained abrasive material showed that …

Go to article

Xenon 147-Nm Resonance Ƒ Value And Trapped Decay Rates, H. M. Anderson, Scott D. Bergeson, D. A. Doughty, J. E. Lawler Jan 1995

Xenon 147-Nm Resonance Ƒ Value And Trapped Decay Rates, H. M. Anderson, Scott D. Bergeson, D. A. Doughty, J. E. Lawler

Faculty Publications

The absorption oscillator strength of the xenon 147-nm resonance transition is measured to be 0.264±0.016. This value is from direct absorption measurements with equivalent widths from ≈ 1 to ≈ 10 cm-1. This ƒ-value measurement is compared to others in the literature and is used in Monte Carlo simulations of trapped decay rates. The simulations include an angle-dependent partial frequency redistribution. The simulation results are compared to trapped decay rates in the literature.

Go to article

New Optical Cell Design For Laser Flash Photolysis Studies In Supercritical Fluids, Steven R. Goates, Milton L. Lee, Qin Ji, Edward M. Eyring, Rudi Van Eldik, Kedika Bal Reddy Jan 1995

New Optical Cell Design For Laser Flash Photolysis Studies In Supercritical Fluids, Steven R. Goates, Milton L. Lee, Qin Ji, Edward M. Eyring, Rudi Van Eldik, Kedika Bal Reddy

Faculty Publications

A high-pressure optical cell has been designed that achieves an effective separation between the chemical sample and the pressurizing medium and system. This design limits possible sample contamination and catalytic effects under supercritical fluid sample conditions. Laser flash photolysis experiments were carried out on molybdenum hexacarbonyl dissolved in supercritical CO2. The thermal ring closure reaction of the species Mo(CO)5L, where L is 2,2- bipyridine was found to proceed at rates comparable to those measured previously in liquid benzene or toluene. Much larger activation volumes were found for the reaction in supercritical CO2 than in liquid toluene.

Go to article

Slow Motion In One-Dimensional Cahn-Morral Systems, Christopher P. Grant Jan 1995

Slow Motion In One-Dimensional Cahn-Morral Systems, Christopher P. Grant

Faculty Publications

In this paper we study one-dimensional Cahn-Morral systems, which are the multicomponent analogues of the Cahn-Hilliard model for phase separation and coarsening in binary mixtures. In particular, we examine solutions that start with initial data close to the preferred phases except at finitely many transition points where the data has sharp transition layers, and we show that such solutions may evolve exponentially slowly; i.e., if ε is the interaction length then there exists a constant C such that in exp(C/ε) units of time the change in such a solution is o(1). This corresponds to extremely slow coarsening of a multicomponent …

Go to article

Semiclassical Quantization Of A Nonintegrable System: Pushing The Fourier Method Into The Chaotic Regime, Karl Sohlberg, Randall B. Shirts Nov 1994

Semiclassical Quantization Of A Nonintegrable System: Pushing The Fourier Method Into The Chaotic Regime, Karl Sohlberg, Randall B. Shirts

Faculty Publications

Semiclassical Einstein–Brillouin–Keller (EBK) quantization of the nonintegrable Hénon–Heiles Hamiltonian succeeds using the Fourier transform method of Martens and Ezra. Two innovations are required for this success: (1) the use of tunneling corrected quantizing actions obtained from an approximate, one-dimensional Hamiltonian and (2) exploitation of intermediate-time approximate quasiperiodicity or "vague tori'' wherein the Fourier transform of chaotic motion over 10–100 vibrational periods allows the determination of frequencies and amplitudes which approximate motion during the time interval. Approximate tori, actions, and EBK energy levels are then straightforward. We use an interpolation method to smooth over small resonance zones that are not expected …

Go to article

A Vlsi Implementation Of A Parallel, Self-Organizing Learning Model, Tony R. Martinez, George L. Rudolph, Linton G. Salmon, Matthew G. Stout Oct 1994

A Vlsi Implementation Of A Parallel, Self-Organizing Learning Model, Tony R. Martinez, George L. Rudolph, Linton G. Salmon, Matthew G. Stout

Faculty Publications

This paper presents a VLSI implementation of the Priority Adaptive Self-organizing Concurrent System (PASOCS) learning model that is built using a multi-chip module (MCM) substrate. Many current hardware implementations of neural network learning models are direct implementations of classical neural network structures - a large number of sample computing nodes connected by a dense number of weighted links. PASOCS is one of a class of ASOCS (Adaptive Self-Organizing Concurrent System) connectionist models whose overall goal is the same as classical neural networks models, but whose functional mechanisms differ significantly. This model has potential application in areas such as pattern recognition, …

Go to article

Spiders: A New User Interface For Rotation And Visualization Of N-Dimensional Point Sets, William A. Barrett, Kirk L. Duffin Oct 1994

Spiders: A New User Interface For Rotation And Visualization Of N-Dimensional Point Sets, William A. Barrett, Kirk L. Duffin

Faculty Publications

We present a new method for creating n-dimensional rotation matrices from manipulating the projections of n-dimensional data coordinate axes onto a viewing plane. A user interface for n-dimensional rotation is implemented. The interface is shown to have no rotational hysteresis.

Go to article

The Structure And Dynamics Of The Cs2 Molecular Ion, Karl Sohlberg, Chan Yibai Sep 1994

The Structure And Dynamics Of The Cs2 Molecular Ion, Karl Sohlberg, Chan Yibai

Faculty Publications

Several common elementary methods of computing molecular properties, prerequisite to molecular dynamics studies, are tested for their validity for CS+2. Judged sufficiently accurate, these methods are then used to aid in investigating the collisionally activated dissociation of CS+2 upon impact with xenon. Rice–Ramsperger–Kassel–Marcus (RRKM) unimolecular decay rate calculations are presented and compared to experimental studies employing collisional activation. RRKM theory is shown to reproduce the experimental results for collision energies near threshold. When corrected for vibrational anharmonicity, the RRKM calculation shows agreement with the experimental results over a slightly wider range of energies. A discussion is given on the applicability …

Go to article

Mesostructure Of Photoluminescent Porous Silicon, David D. Allred, F. Ruiz, C. Vázquez-López, Jesus González-Hernández, G. Romero-Paredes, R. Peña-Sierra, G. Torres-Delgado Jul 1994

Mesostructure Of Photoluminescent Porous Silicon, David D. Allred, F. Ruiz, C. Vázquez-López, Jesus González-Hernández, G. Romero-Paredes, R. Peña-Sierra, G. Torres-Delgado

Faculty Publications

Scanning electron microscopy, atomic force microscopy, and Raman spectroscopy were used to characterize the microstructure of photoluminescent porous silicon (PS) layers formed by the anodic etching (HF:H2O:ethanol), at various current densities, of p-type (100) silicon wafers possessing resitivity in the range 1-2 Ω cm. Existing models for the origin of luminescence in PS are not supported by our observations. Cross-sectional as well as surface atomic force micrographs show the material to be clumpy rather than columnar; rodlike structures are not observed down to a scale of 40 nm. A three-dimensional model of the mesostructure of porous silicon is discussed. Room-temperature …

Go to article

Raman Spectroscopic Study Of The Formation Of T-Mosi2 From Mo/Si Multilayers, Ming Cai, David D. Allred, A. Reyes-Mena Jul 1994

Raman Spectroscopic Study Of The Formation Of T-Mosi2 From Mo/Si Multilayers, Ming Cai, David D. Allred, A. Reyes-Mena

Faculty Publications

We have used Raman spectroscopy, large- and small-angle x-ray diffraction spectroscopy of sputter-deposited, vacuum-annealed, soft x-ray Mo/Si thin-film multilayers to study the physics of silicide formation. Two sets of multilayer samples with d-spacing 8.4 and 2.0 nm have been studied. Annealing at temperatures above 800 °C causes a gradual formation of amorphous MoSi2 interfaces between the Si and Mo layers. The transition from amorphous to crystalline MoSi2 is abrupt. The experimental results indicate that nucleation is the dominant process for the early stage and crystallization is the dominant process after nucleation is well advanced. In the thicker multilayer, a portion …

Go to article

Emitted Current Instability From Silicon Field Emission Emitters Due To Sputtering By Residual Gas Ions, W.I. Karain, Larry V. Knight, David D. Allred, A. Reyes-Mena Jul 1994

Emitted Current Instability From Silicon Field Emission Emitters Due To Sputtering By Residual Gas Ions, W.I. Karain, Larry V. Knight, David D. Allred, A. Reyes-Mena

Faculty Publications

We have fabricated arrays of silicon field emitters using semiconductor lithography techniques. The density of the tips was 10^5/cm^2. The maximum current that can be extracted from each emitter is limited by resistive heating. We have investigated how the electron current emitted changes under constant applied voltage. We found that the current is very sensitive to the vacuum conditions. We attribute this to sputtering of the emitters due to ionized residual gas molecules. The poorer the vacuum, the higher the instability in the current. We studied this phenomenon at 10^6 and 10-x Torr. The model of two concentric spherical shells …

Go to article

A Multi-Chip Module Implementation Of A Neural Network, Tony R. Martinez, George L. Rudolph, Linton G. Salmon, Matthew G. Stout Mar 1994

A Multi-Chip Module Implementation Of A Neural Network, Tony R. Martinez, George L. Rudolph, Linton G. Salmon, Matthew G. Stout

Faculty Publications

The requirement for dense interconnect in artificial neural network systems has led researchers to seek high-density interconnect technologies. This paper reports an implementation using multi-chip modules (MCMs) as the interconnect medium. The specific system described is a self-organizing, parallel, and dynamic learning model which requires a dense interconnect technology for effective implementation; this requirement is fulfilled by exploiting MCM technology. The ideas presented in this paper regarding an MCM implementation of artificial neural networks are versatile and can be adapted to apply to other neural network and connectionist models.

Go to article

Proof Of Correctness For Asocs Aa3 Networks, J. Cory Barker, Tony R. Martinez Mar 1994

Proof Of Correctness For Asocs Aa3 Networks, J. Cory Barker, Tony R. Martinez

Faculty Publications

This paper analyzes adaptive algorithm 3 (AA3) of adaptive self-organizing concurrent systems (ASOCS) and proves that AA3 correctly fulfills the rules presented. Several different models for ASOCS have been developed. AA3 uses a distributed mechanism for implementing rules so correctness is not obvious. An ASOCS is an adaptive network composed of many simple computing elements operating in parallel. An ASOCS operates in one of two modes: learning and processing. In learning mode, rules are presented to the ASOCS and incorporated in a self-organizing fashion. In processing mode, the ASOCS acts as a parallel hardware circuit that performs the function defined …

Go to article

Oscillator Strengths For Fe Ii Transitions At 224.918 And 226.008 Nanometers, Scott D. Bergeson, K. L. Mullman, J. E. Lawler Jan 1994

Oscillator Strengths For Fe Ii Transitions At 224.918 And 226.008 Nanometers, Scott D. Bergeson, K. L. Mullman, J. E. Lawler

Faculty Publications

We report accurate experimental absorption oscillator strengths (f-values) for transitions out of the ground level of Fe II to the z4Do7/2 and z4Do9/2 levels at 224.918 and 226.008 nm (air wavelengths) to be 0.00182(14) and 0.00244(19), respectively. The number in parenthesis is the uncertainty in the last digits. These two lines are important for studying Fe abundances and grain depletions in the interstellar medium. These f-values are determined by combining emission branching fractions with radiative lifetimes. Branching fractions are measured using classical spectroradiometry on an optically thin source. Radiative lifetimes are from …

Go to article

First Prev Next Last