Physics Commons^™

Model Fe(Iii) Porphyrin Systems: Axial Ligation In Oxidized Cytochrome P-450.S, G. C. Papaefthymiou, Richard B. Frankel, S. Foner, S. C. Tang, S. Koch, R. H. Holm

Physics

In an effort to develop useful experimental criteria to distinguish among the viable axial ligation possibilities of O, N, and S coordination in oxidized cytochrome P-450. S (substrate-bound, high-spin), syntheticmodel compounds with O-(Fe(PPIXDME) (OEt) and Fe(PPIXDME) (OC₆H₄NO₂)) and S-(Fe(PPIXDME) (S₆H₄NO₂) and Fe(OEP) (SPh)) donor axial ligands were prepared and studied by Mössbauer spectroscopy. Ferric hemoglobin and myoglobin were used as model compounds with N-axial coordination. The isomer shifts (δ) and quadrupole splittings (ΔE_Q) observed are typical of high-spin Fe(III) porphyrins and are comparable with results …

Synthetic Analogs Of The Active Sites Of Oxidized And Reduced Rubredoxin, Richard B. Frankel, G. C. Papaefthymiou, R. W. Lane, R. H. Holm

Physics

The bischelate monoanion [Fe((SCH₂)₂C₆H₄)₂]^1- contains an unconstrained, near-tetrahedral Fe(III)-S₄ coordination unit (similar to the Fe-S₄ coordinationunit occurring in rubredoxin proteins) and exhibits the Fe(III)/Fe(II) redox couple. Mossbauer parameters at 77 K are isomer shift δ = 0.13 mm/s (relative to iron metal) and electric quadrupole splitting ΔE_Q = 0.57 mm/s. Application of an external magnetic field parallel to the direction of observation at 4.2 K induces a saturation magnetic hyperfine field of - 380 kOe. Upon reduction to the dianion [Fe((SCH₂)₂C …

Review Of Quantum States Of Atoms, Molecules And Solids, M. Eugene Rudd

M. Eugene Rudd Publications

The subjects of atomic, molecular and solid-state physics have only rarely been treated at an advanced level in a single volume. The notable exception, of course, is John C. Slater’s Quantum Theory of Matter. In the present book the three authors, Michael Morrison, Thomas Estle and Neal Lane, stress the unity among these fields by ernphasizing the concept of electronic quantum states in atoms, diatomic molecules and crystalline solids. Such a combination should be of basic interest to students in a variety of scientific fields and also form the basis for more advanced work in those three subjects themselves. …

Ultraviolet Stimulated Thermoluminescent Response Characteristics Of Aluminum Oxide, Edward Ryan

Masters Theses & Specialist Projects

This investigation has demonstrated that some aluminum oxide crystals have high sensitivity and are well suited for detecting and measuring ultraviolet radiation rates significantly less than 0.1 pW/cm2. The thermoluminescent glow curve, linearity of response, and fading of the crystals were determined. An action spectrum was performed to determine the relative sensitivities of several crystals in a range of wavelengths from 230 nm to 546 nm. The sensitivity of the crystals was found to decrease as a function of exposure. An explanation for the decrease in sensitivity due to the presence of high temperature traps is presented. This investigation has …

Energy Dependence Of Amorphizing Implant Dose In Silicon, John R. Dennis, Edward Boyd Hale

Physics Faculty Research & Creative Works

The radiation-induced transformation from crystalline to amorphous silicon was studied using ion implantation. The ion energy was varied from 20 to 180 keV for Li+, N+, Ne+, Ar+, and Kr +. The energy dependence of the critical amorphizing dose was determined by electron spin resonance. Comparison of the data with theoretical calculations of the energy density deposited into atomic processes showed good agreement. This energy-dependent agreement gave evidence that energy density is important to the transformation at both low and high implantation temperatures.

Ultraviolet Stimulated Thermoluminescent Response Characteristics Of Aluminum Oxide, Edward Ryan Iii

Masters Theses & Specialist Projects

This investigation has demonstrated that some aluminum oxide crystals have high sensitivity and are well suited for detecting and measuring ultraviolet radiation rates significantly less than .01 µW/cm².

The thermoluminescent glow curve, linearity of response, and fading of the crystals were determined. An action spectrum was performed to determine the relative sensitivities of several crystals in a range of wavelengths from 230 nm to 546 nm.

The sensitivity of the crystals was found to decrease as a function of exposure. \n explanation for the decrease in sensitivity due to the presence of high temperature traps is presented.

This …

Computer Model Of A Fast Toroidal Plasma Compression, With Application To The Topolotron, H. Mark Nelson, Keith H. Brown, Charles A. Hart

Faculty Publications

The method is developed for a comuputer sequence which models a fast toroidal theta or screw pinch for a highly conducting axially symmetric plasma. The computer sequence takes into account the self-inductances of the plasma and the external conductors which drive the compression as well as the mutual inductance which electromagnetically couples the two. The computer sequence is divided into three phases: a snowplow compression phase, an adiabatic compression phase, and a crowbarred circuit phase. The computer sequence is applied to a topolotron and an example is given of a magnetohydrodynamic equilibrium geometry for which the plasma surface possesses an …

Electron Transmission Studies Of The Negative Ion States Of Substituted Benzenes In The Gas Phase, Kenneth D. Jordan, J.A. Michejda, Paul Burrow

Paul Burrow Publications

Temporary negative ions of benzene, aniline, phenol, anisole, fluoro-, chloro-, and bromobenzene, formed in the gas phase by capture of electrons into the low-lying π* orbitals, are studied by means of electron transmission spectroscopy. The electron affinities are determined and their relative values are interpreted in terms of resonance and inductive effects.

Excitation Of The N=2 State Of Atomic Hydrogen By Electron Impact In The Distorted-Wave Approximation, Ralph V. Calhoun, Don H. Madison, W. Neil Shelton

Physics Faculty Research & Creative Works

The differential cross sections for excitation of the n=2 state of atomic hydrogen by the impact of electrons with energies of 54, 100, 136, and 200 eV are calculated in the distorted-wave approximation with exchange included. Cross sections for excitation of the 2s_1/2, 2p_1/2, and 2p_3/2 states are calculated and summed to give the n=2 differential cross sections. The results of this calculation are compared with previous theoretical calculations and with recent absolute experimental data.

Abstract: Mössbauer Spectroscopy Of Pdh Fe Alloys, M. Weber, C. R. Abeledo, Richard B. Frankel, Brian B. Schwartz

Physics

Large changes in the electron susceptibility of PdH alloys have been observed with increasing H concentration, with important consequences for the magnetic and superconducting properties of these alloys. (1) To observe the effect of the changing spin susceptibility, we have studied PdH Fe alloys with 2, 1 and < 0.1 at. % Fe by Mössbauer spectroscopy in external magnetic fields. Mydosh (2) has reported spin glass behavior in the high Fe concentration alloys and Kondo phenomena in the dilute Fe alloys. For hydrogen-metal ratios < 0.5, α and β phases, with low and high hydrogen content respectively, coexist. For temperatures below T_c of the α phase but above T_c of the β phase, we observe a superposition of a six line spectrum and a single line corresponding to the α and β phases respectively. (3) In an applied field, the β phase magnetizes and both phases have hyperfine fields which extrapolate to …

Mössbauer And Nmr Studies Of Site Substitution And Magnetic Structure Of Fe3-XMnXSi Alloys, K. Raj, V. Niculescu, T. J. Burch, J. I. Budnick, Richard B. Frankel

Physics

The NMR measurements in Fe_3−xMn_xSi alloys show increasingly complex spectra for x > 0.75 due to overlapping signals from Fe, Si and Mn nuclei in various sites. Mössbauer experiments were undertaken to identify the Fe⁵⁷ resonances. The combined NMR and Mössbauer results have been used to elucidate the site substitution and magnetic structure of these alloys for (0 < x < 1.75).

A Comparison Of The Rough Sphere Rotational Diffusion Model With Experimental Results For Liquid Methyl Iodide, Dane R. Jones, Scott L. Whittenburg, C. H. Wang

Chemistry and Biochemistry Faculty Publications

No abstract available.

Electronic And Magnetic Properties Of Amorphous And Crystalline Zr40Cu60-XFeX Alloys, F.R. Szofran, G.R. Gruzalski, John W. Weymouth, David J. Sellmyer, B.C. Giessen

David Sellmyer Publications

Electronic states and localized magnetic moments and their interactions were studied in amorphous and crystalline Zr₄₀Cu_60-xFe_x alloys for 0≤x≤12. Electrical resistivity, magnetic susceptibility, and high-field magnetization measurements were performed. In the dilute crystalline alloys Curie-Weiss behavior is seen in the susceptibility and is associated with localized moments (μ_eff≈3μ_B) on the iron atoms. At higher iron concentrations ferromagnetism is observed. Curie-Weiss behavior also is seen in the susceptibility of the dilute (0eff≈0.7μ_B). There is some evidence that the local environment of the Fe atoms is important and may depend …

Calculated Temperature Of Grid Lateral Wires In Microwave Power Triodes, Jewell Tucker

Masters Theses & Specialist Projects

In microwave power triodes the grid drive power causes grid lateral wire heating. This development calculates the temperature of the wire as a function of the drive power, physical dimensions and characteristics of the wire material, for the following boundary conditions:

I. Constant grid drive, grid lateral wire of infinite length not connected to a heat sink.

II. Same as I except the wire is of finite length brazed to a grid frame.

III. The grid excitation in the form of pulses, and the grid lateral wire of finite length brazed to a grid frame.

the equations were verified experimentally …

Behavior Of A Manganin Coil At Elevated Temperatures And Pressures, Jonathan D. Weiss, Daniel L. Decker, H. B. Vanfleet

Faculty Publications

We have determined the temperature dependence in the first-order pressure coefficient of a manganin coil to be dBetaB/dT= (4.2±0.8) ×10^-7 (kbar degrees C)^-1 in the equation R (T,P) =R (T,0)(1+BetaP+GammaP2), where R (T,P) is the coil resistance at temperature T and pressure P. The measurements were performed by simultaneously measuring the coil resistance and temperature at the transitions of mercury and bismuth, which were observed by differential thermal analysis.

Supralinearity Of Thermoluminescent Dosimeters, Leif Larsson, Robert Katz

Robert Katz Publications

The supralinear response of thermoluminescent dosimeters (TLDs) after irradiation with gamma- or beta-rays can be decomposed by use of the cumulative Poisson distribution into a sum of 1-or-more and 2-or-more hit components, suggesting the coexistence of both types of trap structures. Following the response of other 1-hit detectors, and of biological cells to energetic heavy ions, we expect and find that the supralinear response tends to disappear with alpha particle, and with neutron irradiation, and that the supralinear, or 2-hit, component tends to be more responsive to high LET (Linear Energy Transfer) radiations. Since the response of biological cells to …

The Quantum Defect Theory Approach, Anthony F. Starace

Anthony F. Starace Publications

The Quantum Defect Theory (QDT) is a method of using the analytically known properties of excited electrons moving in a pure Coulomb field to describe atomic photoabsorption and electron-ion scattering processes in terms of a few parameters. These parameters may be determined either from experimental data or from ab initio theoretical calculations. In addition, they are usually nearly independent of energy in the threshold energy region (i.e., within a few eV of the atomic ionization threshold). Thus the determination of these parameters at any single energy suffices to predict the variation with energy of numerous atomic properties in the threshold …

Cross Sections For Excitation Of Atomic Hydrogen To The N=2, 3, And 4 States By 15-200-Kev Protons, John T. Park, Judith E. Aldag, Jacob M. George, Jerry Peacher

Physics Faculty Research & Creative Works

Cross sections for the processes H⁺+H(1 s)H⁺+H*(n = 2, 3, 4) have been extracted from the energy-loss spectra of 15- to 200-keV protons by using a spectrum-fitting technique. Absolute cross sections have been obtained by normalization of the spectra to the theoretical cross section through the use of the Born approximation at 200 keV. The cross-section curves are very similar in shape with maxima at 60 keV. The results have been compared with available theoretical calculations. The n = 2 and n = 3 cross-section measurements are in very good agreement in curve shape with Glauber-approximation …

Frequency-Mixing Detection (Fmd) Of Polarization-Modulated Light, R. M.A. Azzam

Electrical Engineering Faculty Publications

When a light beam whose polarization and intensity are weakly modulated at a frequency ω_m passes through a periodic analyzer of frequency ω_a(<ω_m) and the transmitted flux is linearly detected, the resulting total signal S_t consists of two components: (i) a periodic baseband signal S_bb with harmonics of frequencies nω_a (n = 0,1,2,…) and (ii) an amplitude-modulated-carrier signal δS_mc with center (carrier) frequency ω_m and sideband frequencies at ω_m ± nω_a(n = 1,2,…). In this paper we show that the average polarization of the beam is determined …

Systematic Evaluation Of Cellular Radiosensitivity Parameters, R. A. Roth, S. C. Sharma, Robert Katz

Robert Katz Publications

Cellular radiosensitivity parameters of the track structure theory of Katz and co-workers are evaluated from a sum of squares minimizing computer program for nonlinear models. Based on these observations, suggestions are presented for efficient experiment design for the determination of these parameters from track-segment bombardments of high LET radiations.

Comparison Of Experimental And Theoretical Electron Ejection Cross Sections In Helium By Proton Impact From 5 To 100 Kev, M. Eugene Rudd, Don H. Madison

Physics Faculty Research & Creative Works

Absolute values of doubly differential cross sections are obtained for electron production in helium by 5- to 100-keV proton impact. The measured values along with earlier data at higher energies are compared with theoretical plane-wave Born-approximation functions obtained from a Hartree-Fock potential. Not only is good agreement obtained at high impact energies (above 300 keV), but fairly good agreement is found at low energies (below about 20 keV). For electrons ejected in the backward hemisphere, unexpectedly poor agreement is noted at intermediate energies where the measured cross sections dip to 50% of the calculated values in some cases. Singly differential …

Modulated Generalized Ellipsometry, R. M.A. Azzam

Electrical Engineering Faculty Publications

We extend ellipsometry to the direct measurement of small perturbations of the Jones matrix of any linear nondepolarizing optical sample (system) subjected to a modulating stimulus such as temperature, stress, or electric or magnetic field. The methodology of this technique, to be called Modulated Generalized Ellipsometry (MGE), is presented. First an ellipsometer with arbitrary polarizing and analyzing optics is assumed, and subsequently the discussion is specialized to a conventional ellipsometer having either the polarizer-sample-analyzer (PSA) or the polarizer-compensator-sample-analyzer (PCSA) arrangement. MGE provides the tool for the systematic study of thermo-optical, piezo-optical, electro-optical, magneto-optical, and other allied effects for both isotropic …

Observation Of Vibrationally Excited Nitrogen With A Simplified Electron Transmission Apparatus, J.A. Michejda, Paul Burrow

Paul Burrow Publications

A simple electron transmission apparatus is used to observe vibrationally excited N₂ in the first two vibrational levels. The method is based on the pronounced peaks appearing in the total electron scattering cross section in the range of energy 2–4 eV. Because of the wide spacing between these peaks, good energy resolution is not required and measurements can be performed without an electron monochromator.

Reply To “Comments On ‘Theoretical Study Of Impurity-Induced First-Order Raman Spectra For The Alkali Halides’”, John R. Hardy, Arnold Karo

John R. Hardy Papers

This is a reply to the preceding comment by Page on the relative merits of the breathing-shell and deformation-dipole models for predicting defect-activated first-order Raman spectra. We show that when both models are parametrized in the same fashion the agreement between theory and experiment is comparable.

Metamagnetism In Single Crystal Γ-Co(Pyridine)2Cl2, S. Foner, Richard B. Frankel, W. M. Reiff, H. Wong, Gary J. Long

Physics

Small (≤1 mg) single crystals of γ-Co(pyr)₂Cl₂ have been grown and measurements of magnetic moment vs applied field H and temperature have been made for 0≤H≤54 kG and 1.25 K≤T≤4.2 K. At 1.25 K, metamagnetic transitions are observed along the a-axis at ~700 G; along the b-axis at both ~800 and ~1500 G; and along the c-axis at ~4 kG. The low field susceptibilities show a maximum at T≃3.4 K for each orientation. Magnetic saturation is not achieved at 54 kG; about 2.5 µ_B is achieved along the a*- or b-axes, whereas a lower moment is …

Hyperfine Interactions In Antiferromagnetic Eute Using The Te-125 Mossbauer Resonance, N. A. Blum, Richard B. Frankel

Physics

Europium telluride crystallizes in the NaCl structure and is antiferromagnetic with a Néel temperature TN of 9.6 K. We have used the 35.5 keV Møssbauer transition in Te-125 to examine the nature of the spontaneous magnetic moment which has been observed in conducting samples below TN. At 80 K the Mössbauer resonance spectrum consisted of a single absorption line comparable in width with the spectrum of nonmagnetic cubic ZnTe, indicating the absence of a significant quadrupole splitting at this temperature. At 4.2 K the line-width increased by a factor of 1.5, which is equivalent to a single magnetic hyperfine field …

Photoinization Cross Sections For Atomic Chlorine Using An Open-Shell Random-Phase Approximation, Anthony F. Starace, Lloyd Armstrong Jr.

Anthony F. Starace Publications

The use of the random-phase approximation with exchange (RPAE) for calculating partial and total photoionization cross sections and photoelectron angular distributions for open-shell atoms is examined for atomic chlorine. Whereas the RPAE corrections in argon (Z=18) are large, we find those in chlorine (Z=17) to be much smaller due to geometric factors. Hartree-Fock calculations with and without core relaxation are also presented. Sizable deviations from the close-coupling results of Conneely are found.

Debye–Hückel Theory For Rigid‐Dipole Fluids, John D. Ramshaw

Physics Faculty Publications and Presentations

The dipolar analog of classical linearized Debye–Hückel theory is formulated for a finite fluid system of arbitrary shape composed of rigid polar molecules. In contrast to the ionic case, the dipolar Debye–Hückel (DDH) theory is nonunique due to an inherent arbitrariness in the choice of a local field E*. This nonuniqueness is expressed in terms of a parameter ϑ related to the ellipticity of the spheroidal cavity used to define E*. The theory then leads to an expression for the direct correlation function c (ϑ) as a function of ϑ. Only the short‐range part of c (ϑ) depends upon ϑ; …

Multiple Rainbows From Single Drops Of Water And Other Liquids, Jearl D. Walker

Physics Faculty Publications

The scattering of light by spherical drops and the theory of rainbows are reviewed in detail to predict the angular positions of rainbows from single drops. The angular positions of the first 13 rainbows of water, observed from a drop suspended in a student spectrometer, were compared to these theoretical positions. Since the rainbows were dependent on the refractive index, the positions shifted with drops of other fluids having other refractive indices. Light corn syrup yielded 11 rainbows, including the 17th-order one. The light emerging from the drops was white except for the multicolors of the rainbows and the faint …

Hall-Effect Measurements In Cd-Implanted Gaas, B. K. Shin, David C. Look, Y. S. Park, J. E. Ehret

Physics Faculty Publications

Cadmium ions were implanted in GaAs crystals at 135 keV to doses ranging from 10¹² to 10¹⁶ ion/cm² at room temperature. Sheet‐resistivity and Hall‐effect measurements were carried out as a function of temperature, 4.2–300°K, after annealings at 700, 800, or 900°C in an Ar ambient. The sample surfaces were protected with pyrolytically deposited Si₃N₄. Significant p‐type conduction was observed when samples with doses ≳10¹³cm⁻² were annealed at ≳700°C. For doses below 10¹⁴ cm⁻² nearly complete electrical activity was attained after an 800–900°C anneal. The Cd profiles were …