Physical Sciences and Mathematics Commons^™

Synthetic Analogs Of The Active Sites Of Iron-Sulfur Proteins. Viii. Some Electronic Properties Of [Fe4S4(Sr)4]3; Analogs Of Reduced Bacterial Ferredoxins, R. B. Frankel, T. Herskovitz, B. A. Averill, R. H. Holm, P. J. Krusic, W. D. Phillips

Physics

One-electron reduction of the synthetic tetramers [Fe₄S₄(SR)₄]^2- (R = CH₂Ph, Ph), by chemical and electrochemical methods affords the corresponding trianions. The collective results from optical, electron paramagnetic resonance, and Mössbauer spectroscopy, when compared to available data for reduced 4-Fe and 8-Fe ferredoxin proteins and super-reduced Chromatium high-potential protein, reveal that [Fe₄S₄(SR)₄]^3- are electronic analogs of the [Fe₄S₄(S-Cys)₄] active sites of these proteins.

Eikonal Distorted-Wave Calculation For The Excitation Of H By He, Jerry Peacher, Richard H. Shields

Physics Faculty Research & Creative Works

The eikonal distorted-wave Born approximation developed recently by Chen, Joachain, and Watson is applied to hydrogen excitation by helium impact in the intermediate-energy range. The differential and total cross sections for the excitation of the hydrogen atom to the 2s, 2p_±, or 2p₀ state by helium impact are presented. These results are compared to experiment and previous calculations. The differential cross section for the excitation of hydrogen to the 2s state compares well with the experimental data of Thomas and Sauers in shape and slope, but has a discrepancy in magnitude.

Photoelectron Angular Distributions, Cross Sections, And Branching Ratios For Atomic Oxygen, Anthony F. Starace, Steven T. Manson, David J. Kennedy

Anthony F. Starace Publications

Theoretical calculations of the angular distribution of photoelectrons ejected from the 2p subshell of atomic oxygen for photoelectron kinetic energies 0≤ε≤30 Ry are presented using both Hartree-Fock (HF) and Herman-Skillman (HS) wave functions. Owing to the weakness of anisotropic electron-ion interactions, as evidenced by small differences between HF photoelectron phase shifts for alternative outgoing channels, the simple HS calculation of the angular-distribution asymmetry parameter is found to agree to within ≲ 0.1 with the HF calculations. Photoionization cross sections and photoelectron branching ratios have also beem computed in both the HF and HS approximation for the 2p subshell …

Heat Transfer Across Carbon - Liquid Helium I Interface, Constantine Antonopoulos

Dissertations and Theses

Carbon samples were electrically heated while immersed in liquid helium I. Their temperature rise was observed on an oscilloscope as a function of the time after the onset of the electric current. There was no indication of the temperature overshoot previously reported for the case of bismuth in liquid helium.

Reasons are presented for the difference in behavior of carbon and bismuth.

Vibration Damping Characteristics Of Typical Harpsichord Strings, Jack Lee Simmons

Dissertations and Theses

Present-day builders of harpsichords disagree as to the use of iron or carbon-steel wire in their attempt to duplicate the tonal qualities of the early 16th century instruments. The variations in tone produced by vibrating iron and steel wires may be due, at least in part, to differences in their decay characteristics. A wire was set into vibration by placing a section in a magnetic field and passing a variable-frequency alternating current through it. A condition of resonance was established by appropriately selecting frequencies, lengths, and tensions that would simultaneously satisfy the relationship: fr = n/2L(T/p)1/2. Then measurements of decay …

Photoelectron Angular Distributions As A Probe Of Anisotropic Electron-Ion Interactions, Dan Dill, Steven T. Manson, Anthony F. Starace

Anthony F. Starace Publications

Expressions are given for atomic photoelectron angular distributions in LS coupling in which the role of anisotropic final state electron-ion interactions emerges explicitly. Calculations of photoelectron angular distributions for atomic sulfur are presented in which these anisotropic interactions produce clear deviations from the predictions of the Cooper-Zare model. Such effects are expected to be a general feature of photoelectron angular distributions for most open-shell atoms.

Electrical Characteristics Of Al‐Implanted Znse, B. K. Shin, Y. S. Park, David C. Look

Physics Faculty Publications

Aluminum was implanted in ZnSe at 90 keV to a dose of 10¹⁵ ions/cm² at room temperature. Hall‐effect and sheet‐resistivity measurements were made on the samples for various annealing conditions. The implanted layer is found to be degenerate n‐type having a sheet resistivity of ∼10³ Ω/□, after annealing at 900°C for 4 h.

Electron Detachment In Low-Energy Collisions Of H- And D- With He, S. K. Lam, John B. Delos, L. Champion, L. D. Doverspike

Arts & Sciences Articles

Measurements and calculations have been made of elastic scattering and electron detachment in collisions of H− and D− with He at energies of 5-120 eV. The measurements show no other inelastic processes occurring in this energy range. The mechanism responsible for electron detachment is assumed to be the crossing of the H− bound state with the continuum of free states; the bound state is then assigned a complex energy. The measured elastic scattering differential cross section shows no structure except at Eθ∼200 eV deg, where there is a region of downward curvature in the graph of logσ vs θ. This …

A Theoretical Proton-Proton Pair Production Cross-Section Calculation, Jay W. Phippen

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The calculation of both electron-pair and muon-pair production cross-sections was made using Feynman's quantum electrodynamics. Pseudo-scaler coupling was used between the nucleons and vector coupling was used between the photon and the Fermions. The protons were considered as Dirac particles and radiative corrections were omitted.

Eight fourth-order Feynman-Dyson diagrams were used. The subsequent sixty-four TRACES were reduced to seven basic topologically different TRACES. From the seven basic TRACES, it was possible to generate the sixty-four TRACES by the proper permutations of the variables.

With the mathematics and the corresponding computer programs written down, data (energies and momenta which represent the …

A Method For Measuring The Electrical Conductivity Of A Shocked Liquid, Richard James Hassman

Physics & Astronomy ETDs

Development of a simple technique for the measurement of the gross electrical conductivity of a shock compressed liquid is attempted. A cell containing the sample is constructed from glass cylinders and aluminum foil. The foil is sandwiched between two cylinders of the same diameter to form a two compartment cylinder. The cylinder is mounted on a metal target plate. With both chambers of the system full of liquid, only insignificant reflections can arise from the sample-foil interface. A voltage is placed across the cell between the foil and the target plate, and the change in voltage as the shock front …

Angular Distribution Of Photoelectrons From Atomic Oxygen, Nitrogen, And Carbon, Steven T. Manson, David J. Kennedy, Anthony F. Starace, Dan Dill

Anthony F. Starace Publications

The angular distributions of photoelectrons from atomic oxygen, nitrogen and carbon are calculated. Both Hartree-Fock and Hartree-Slater (Herman-Skillman) wave functions are used for oxygen, and the agreement is excellent; thus only Hartree-Slater functions are used for carbon and nitrogen. The pitch angle distribution of photoelectrons is discussed and it is shown that previous approximations of energy independent isotropic or sin² θ distributions are at odds with our results, which vary with energy. This variation with energy is discussed as is the reliability of these calculations.

Hand Held Probe For Use In Electrical Sensing Of Plane Coordinates, George S. Hurst

Physics and Astronomy Faculty Patents

A probe with a puncturing, electrically conducting needle is constructed to enable the user, whether right or left handed, to position the needle rapidly and accurately at a selected coordinate of a sensor package.

The Use Of Transactional Analysis With Inquiry Methods In Physics Teaching, Robert Fuller, Ward L. Sims

Robert G. Fuller Publications

We now offer a course that combines an inquiry approach to physics with elementary school science teaching methods and transactional analysis. Our course carries three semester credits in elementary science methods and three semester credits in physics, a total of nine contact hours per week. In previous interim courses the very positive response we have had from our students, i.e., the excitement in discovering some real physics for themselves, and their decision to use the tools of transactional analysis to say "OK" to themselves and physics, leads us to believe that our course can serve as a useful model for …

Studies Of The Potential Curve Crossing Problem. Iii. Collisional Spectroscopy Of Close Crossings, John B. Delos

Arts & Sciences Articles

Using a previously developed semiclassical theory of electronic excitations, the cross sections that result from potential-curve crossings are calculated for a model system. The phenomena appearing in the differential cross sections are displayed and discussed.

Theoretical And Experimental Studies Of The Second-Order Raman Spectra Of Cscl, Csbr, And Csi, B.S. Agrawal, Roger D. Kirby, John R. Hardy

Roger Kirby Publications

Measurements of the second-order Raman spectra of CsCl, CsBr, and CsI have been made at both 300 and 80 °K. From these the three independent spectral components, A 1g, E g, and T 2g, have been determined for all three crystals at both temperatures. A theoretical interpretation of these data has been carried out using the phenomenological Born-Bradburn model to describe the Raman polarizability tensor and the deformation-dipole model to provide the lattice-dynamical eigendata. We have found it possible to obtain an excellent description of the observed spectra retaining 16 of the first- and second-neighbor polarizability derivatives in the Born-Bradburn …

An Ok Science Teacher, Robert Fuller

Robert G. Fuller Publications

Many elementary school teachers feel insecure and unsure in their teaching of science, i.e., they have NOT OK feelings about themselves and science. These feelings are based on the teachers' previous science experiences and on their interactions with other persons in science courses. The improvement of elementary school science programs depends upon the teacher's ability to deal effectively with his feelings about science. A complete science education program for an elementary teacher includes three components: (1) science content, (2) science methods that take into consideration the intellectual development of children, and (3) a practical psychology for developing positive human attitudes …

Abstract: Phase Transitions In Fecl2·2h2O In External Magnetic Fields: Mössbauer Spectroscopy, L. D. Kandel, M. A. Weber, Richard B. Frankel, C. R. Abeledo

Physics

Monoclinic FeCl₂·2H₂O orders antiferromagnetically at T_N = 23 K, and the magnetic structure consists of two sublattices of -FeCl₂-chains lying along the c-axis. The coupling along the chains is ferromagnetic with weak antiferromagnetic coupling between chains. Application of an external magnetic field along the easy axis (a) induces phase transitions at H₁ = 39 kOe and at H₂ = 46 kOe.

We report the observation of the three phases using the Mössbauer effect in a single crystal of FeCl₂·2H₂O cut parallel to the c-axis and placed at …

Phonon-Induced Second-Order Raman Scattering In Lif, T.P. Sharma, Roger D. Kirby, Sitaram Jaswal

Roger Kirby Publications

We have studied experimentally and theoretically the second-order Raman spectra of LiF. Theoretical calculations based on Born and Bradburn's approach explain the observed spectra fairly well when all the eight-nearest-neighbor, only two of the fifteen-next-nearest-neighbor negative-negative, and none of the fifteen next-nearest-neighbor positive-positive polarizability coefficients are used as adjustable parameters.

Pb And Bi L-Subshell Ionization Cross-Section Ratios Versus Proton Bombarding Energy From 0.5 To 4 Mev, Don H. Madison, A. B. Baskin, C. E. Busch, Stephen M. Shafroth

Physics Faculty Research & Creative Works

Experimental ratios of L-subshell cross sections are given for ionization of lead and bismuth by 0.5-4-MeV-proton bombardment. The ratio of the L_II to L_I cross sections exhibits a maximum near 1.75 MeV. Individual subshell cross sections are obtained from the experimental ratios and previous total-cross-section data. These subshell ratios and cross sections are compared with the theoretical predictions of the plane-wave Born approximation using nonrelativistic hydrogenic wave functions, of the binary-encounter approximation scaled from Mg K-shell cross sections, and of the binary-encounter approximation scaled from cross sections obtained using L-shell velocity distributions. It was found that both approximations …

Diffusion-Controlled Intrachain Reactions Of Polymers. I Theory, Gerald Wilemski, Marshall Fixman

Physics Faculty Research & Creative Works

A theory of diffusion-controlled intramolecularly catalyzed reactions of polymer chains in dilute solution is formulated. A closure approximation yields a soluble integral equation for (essentially) the transient rate of the reaction. The time dependent solution consists of a sum of simple exponential terms whose coefficients and decay constants can be readily calculated. The theory is also applied to luminescence quenching and ring-chain interconversion.

Diffusion-Controlled Intrachain Reactions Of Polymers. Ii Results For A Pair Of Terminal Reactive Groups, Gerald Wilemski, Marshall Fixman

Physics Faculty Research & Creative Works

The formulas and results of the preceding paper are used to calculate the rate of reaction between reactive groups attached to the ends of a polymer chain. Extensive numerical calculations have been made for both transient rate processes and steady state luminescence quenching. The results are restricted to chains in dilute solution, in either the free draining or nondraining limits and with no excluded volume forces present. A discussion of the qualitative effects of excluded volume forces on the results is included. The results suggest that experimental studies of these processes may be feasible.

Eikonal Approximation Applied To Atom-Atom Excitation At Intermediate Energies: Excitation Of H By H, Richard H. Shields, Jerry Peacher

Physics Faculty Research & Creative Works

The eikonal distorted-wave Born approximation (DWBA) developed recently by Chen, Joachain, and Watson is applied to atom-atom excitation in the intermediate energy range. In this paper the excitation of a hydrogen atom to the 2s, 2p_±, or 2p₀ state by hydrogen impact is considered. Differential cross sections are presented. Total cross sections are presented and compared to previous calculations. It is shown that the eikonal DWBA results for the total cross section approach the two-state distortion-approximation results in the limit of high energy and very-small-angle scattering.

Mössbauer Spectroscopy Of Magnetic Phases In Fecl2 · 2h2O, L. Kandel, M. A. Weber, Richard B. Frankel, C. R. Abeledo

Physics

Mössbauer spectroscopy of the three magnetic phases of single crystal FeCl₂ · 2H₂ in external magnetic fields at 4.2 K is reported.

Effect Of Virtual 4d-Shell Excitations On Rare Earth Spectra, Anthony F. Starace

Anthony F. Starace Publications

Ab initio energies for electric dipole transitions 4d¹⁰ (¹S₀) → 4d⁹4f J = 1 in triply-ionized lanthanum have been calculated by constructing an effective interaction, acting within the configuration 4d⁹4f, that incorporates effects of virtual 4d-shell excitations to all orders of perturbation. Virtual 4d-shell excitations, included within the random phase approximation, and virtual excitations to singly-excited configurations 4d⁹εf are found to reduce the ordinary electrostatic interaction by 38% for the ¹P₁ term of 4d⁹4f, by 6% for the ³D₁ term, and by 3% …

Erratum: Semiclassical Study Of The Vibrational Excitation Of H2 In Collision With He (J. Phys. B: Atom. Molec. Phys. (1974) 7 (398405)), Gordon W. F. Drake, C. S. Lin

Physics Publications

No abstract provided.

Semiclassical Study Of The Vibrational Excitation Of H2 In Collision With He, Gordon W. F. Drake, C. S. Lin

Physics Publications

The vibrational excitation and dissociation probabilities of H2 in a collinear collision with He are calculated, using the semi-classical time-dependent method along with the accurate H2 molecular potential of Kolos and Wolniewicz (1965, 1968). The complete set of bound and continuum eigenfunctions are represented in terms of a truncated basis set of harmonic oscillator functions. The results differ significantly from the Morse potential quantum mechanical calculations of Clark and Dickinson (1973). In addition, a state-dependent interaction potential is suggested to allow for the different average sizes of the H2 molecule in its initial and final states. The state dependent potential …

Leading Radiative Correction To The Magnetic Dipole Transition Probability, Gordon W. F. Drake

Physics Publications

It has recently been suggested that a radiative correction of relative order ln may contribute to the 1s2sS13-1s2S01 magnetic dipole transition of the heliumlike ions. The low-frequency contributions to the correction are evaluated and shown to vanish. © 1974 The American Physical Society.

Cross Sections For L2,3 Auger Emission In 22- To 300-Kev H+ + Ar Collisions, M. Eugene Rudd

M. Eugene Rudd Publications

Measurements of total and differential L_2,3 Auger cross sections for H⁺ + Ar collisions at 22 - 150 keV are presented. Additional values of these cross sections were calculated from data in earlier investigations by Volz and Rudd and by Crooks and Rudd up to 300 keV. Angular distributions are found to be isotropic. Over most of the energy range the total Auger cross sections are a factor of 2 smaller than predicted by Garcia's binary-encounter calculations.

Observation Of Persistent Currents In A Saturated Superfluid Film, Robert Hallock, R. K. Galkiewicz

Robert Hallock

We report the first observation of a persistent flow around a closed path consisting entirely of saturated superfluid helium film in a macroscopic geometry in which the saturated vapor was in unconstrained proximity to the film

Quasi-Isothermal Superfluid Film Oscillations, Robert Hallock

Robert Hallock

We have carried out a detailed study of the frequency and damping of the oscillations in levels of two reservoirs of HeII which are coupled only via the mobile superfluid film. Our experiments cover the temperature range 1.2