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1978

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Articles 1 - 30 of 85

Full-Text Articles in Physics

Perturbation Theory In A Strong-Interaction Regime With Application To 4d-Subshell Spectra Of Ba And La, Göran Wendin, Anthony F. Starace Dec 1978

Perturbation Theory In A Strong-Interaction Regime With Application To 4d-Subshell Spectra Of Ba And La, Göran Wendin, Anthony F. Starace

Anthony F. Starace Publications

We investigate the behavior of a bound electron–hole excitation in an energy region where the response of the system is highly resonant and shows strong collective behavior. Formulae for calculating discrete energy levels and wavefunctions are presented for the case where the perturbation is strong enough to change the nodal structure of the perturbed wavefunctions relative to that of the unperturbed wavefunctions. This change in nodal structure requires a renaming of the associated atomic states. Neglect of such renaming is shown to have been at the root of a recent controversy between differing interpretations, based on alternative calculational procedures, of …

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Vibrational And Rotational State Dependence Of Dissociative Attachment In E-H2 Collisions, J. M. Wadehra, J. N. Bardsley Dec 1978

Vibrational And Rotational State Dependence Of Dissociative Attachment In E-H2 Collisions, J. M. Wadehra, J. N. Bardsley

Physics and Astronomy Faculty Research Publications

Resonant scattering theory is applied to the calculation of e-H2 dissociative attachment cross sections near threshold for several vibrational and rotational states of the H2 molecule. Typical values just above threshold are, in cm2, 2.8×10−21 for the ground state (v=0, J=0), 8.3×10−20 for (1, 0), 1.0×10−18 for (2, 0), and 3.5×10−20 for (0, 10). The effect of rotational excitation is found to be significant, although it is not as large as suggested by Chen and Peacher.

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Diffusion Of Nickel In Silicon Below 475 °C, G. L.P. Berning, L. L. Levenson Dec 1978

Diffusion Of Nickel In Silicon Below 475 °C, G. L.P. Berning, L. L. Levenson

Physics Faculty Research & Creative Works

Nickel films were deposited on (100) and (111) surfaces of single-crystal silicon and were then annealed. The conditions under which the nickel is deposited determine whether or not an NiSi compound forms on annealing. It is postulated that defects are necessary for the formation of an NiSi compound at annealing temperatures below at least 475 °C, although the presence of defects may not necessarily cause the formation of a silicide. For substrate temperatures below 70 °C, defects are created during the vapor deposition of nickel on silicon. These defects always result in the formation of nickel silicide when the sample …

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High-Flux Beam Source Of Fast Neutral Helium, D. W. Fahey, Laird D. Schearer, William F. Parks Dec 1978

High-Flux Beam Source Of Fast Neutral Helium, D. W. Fahey, Laird D. Schearer, William F. Parks

Physics Faculty Research & Creative Works

A high-flux beam source of fast neutral helium has been constructed by extending the designs of previous authors. The source is a dc or pulsed electric discharge in an expanding gas nozzle. The beam produced has a flux on the order of 1015 atoms/ssr and a mean velocity on the order of 107 cm/s. The composition of the beam has been determined by the use of particle detectors and by the observation of the excitation of certain target gases. An upper bound of 3.7*10-5 has been estimated for the He(2 3S1)/He(1S0) beam density ratio and a value of 0.2 found …

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Principal Angle, Principal Azimuth, And Principal-Angle Ellipsometry Of Film-Substrate Systems, R. M.A. Azzam, A.-R. M. Zaghloul Dec 1978

Principal Angle, Principal Azimuth, And Principal-Angle Ellipsometry Of Film-Substrate Systems, R. M.A. Azzam, A.-R. M. Zaghloul

Electrical Engineering Faculty Publications

When the film thickness is considered as a parameter, a system composed of a transparent film on an absorbing substrate (in a transparent ambient) is characterized by a range of principal angle ø¯min ≤ ø¯ ≤ ø¯max over which the associated principal azimuth ψ¯ varies between 0° and 90° (i.e., 0° ≤ ψ¯ ≤ 90°) and the reflection phase difference Δ assumes either one of the two values: +π/2 or −π/2. We determine the principal angle ø¯(d) and principal azimuth ψ¯(d) as functions of film thickness d for the vacuum-SiO2-Si system at …

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Propagation Of Partially Polarized Light Through Anisotropic Media With Or Without Depolarization: A Differential 4 × 4 Matrix Calculus, R. M.A. Azzam Dec 1978

Propagation Of Partially Polarized Light Through Anisotropic Media With Or Without Depolarization: A Differential 4 × 4 Matrix Calculus, R. M.A. Azzam

Electrical Engineering Faculty Publications

We extend the scope of the Mueller calculus to parallel that established by Jones for his calculus. We find that the Stokes vector S of a light beam that propagates through a linear depolarizing anisotropic medium obeys the first-order linear differential equation dS/dz = mS, where z is the distance traveled along the direction of propagation and m is a 4 × 4 real matrix that summarizes the optical properties of the medium which influence the Stokes vector. We determine the differential matrix m for eight basic types of optical behavior, find its form for the most general anisotropic nondepolarizing …

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Crystalline To Amorphous Transformation In Ion-Implanted Silicon: A Composite Model, John R. Dennis, Edward Boyd Hale Dec 1978

Crystalline To Amorphous Transformation In Ion-Implanted Silicon: A Composite Model, John R. Dennis, Edward Boyd Hale

Physics Faculty Research & Creative Works

The transformation of silicon to the amorphous state by implanted ions was studied both experimentally and theoretically. Experimentally, the amount of transformed silicon and the critical ion dose necessary to amorphized the entire implanted layer were determined by ESR. How the critical dose varies with ion mass (Li, N, Ne, Ar, and Kr), ion energy (20-180 keV), and implant temperature (77-475 K) was determined. Theoretically, several phenomenological models were used to analyze these data. The overlap-damage model was used to determine the critical dose from the data, the size of the amorphous region around the ion track, and the degree …

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A Feasibility Study Concerning The Use Of Alternate Energy Sources In Taiwan, Li-Juan Lee Dec 1978

A Feasibility Study Concerning The Use Of Alternate Energy Sources In Taiwan, Li-Juan Lee

Masters Theses

No abstract provided.

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Nmr Instrumentation With Solid State Devices, Syed M. Ahmed Dec 1978

Nmr Instrumentation With Solid State Devices, Syed M. Ahmed

Masters Theses

No abstract provided.

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Role Of Low-Energy Two-Body Virtual States In Three-Particle Scattering Situations, James A. Lock Dec 1978

Role Of Low-Energy Two-Body Virtual States In Three-Particle Scattering Situations, James A. Lock

Physics Faculty Publications

A model three-particle scattering situation consisting of a projectile incident on a target bound to a residual core was considered under the assumptions that there was a low-energy virtual state in the projectile-target channel, that the projectile and core did not interact, and that the projectile-target and target-core interactions were s-wave separable interactions. When the appropriate Faddeev equations were solved by inversion, an enhancement was found in the three-body elastic cross section for virtual state energies less than or comparable to the target-core binding energy. This enhancement was determined to be kinematical in origin.

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Electron Attachment In Dilute Fluorine-Helium Mixtures, Kaare J. Nygaard, Scott R. Hunter, John L. Fletcher, Stephen R. Foltyn Dec 1978

Electron Attachment In Dilute Fluorine-Helium Mixtures, Kaare J. Nygaard, Scott R. Hunter, John L. Fletcher, Stephen R. Foltyn

Physics Faculty Research & Creative Works

We have made an absolute determination of the electron attachment coefficient η (cm-1) in helium containing 0.1-1% fluorine covering an E/N range from 3Td-17Td. At an estimated average energy of 5 eV we find a rate coefficient equal to (7.5±1.5) x10-10 cm3/sec.

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Chemical Vapor Deposited Amorphous Silicon For Use In Photothermal Conversion, David D. Allred, D. C. Booth, M. Janai, G. Weiser, B. O. Seraphin Nov 1978

Chemical Vapor Deposited Amorphous Silicon For Use In Photothermal Conversion, David D. Allred, D. C. Booth, M. Janai, G. Weiser, B. O. Seraphin

Faculty Publications

Efficient photothermal conversion requires surfaces of high solar absorptance and low thermal emittance. This can be accomplished by the tandem action of a good infrared reflector overlaid by a film of sufficient solar absorptance that is transparent in the infrared. Crystalline silicon is a suitable candidate for the absorber layer. Its indirect band gap, however, results in a shallow absorption edge that extends to far into the visible. In contrast, the absorption edge of amorphous silicon is steeper and located farther into the infrared, resulting in a larger solar absorptance. We report on the fabrication of amorphous silicon absorbers by …

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Chemical Vapor Deposited Molybdenum Films For Use In Photothermal Conversion, David D. Allred, G. E. Carver, B. O. Seraphin Nov 1978

Chemical Vapor Deposited Molybdenum Films For Use In Photothermal Conversion, David D. Allred, G. E. Carver, B. O. Seraphin

Faculty Publications

High infrared reflectance, coupled with higher solar absorptance, is required for efficient photothermal conversion. Converters can be fabricated by depositing an absorber on a highly reflecting metal. The absorber functions in the visible, yet becomes transparent in the near infrared, allowing the metal to suppress the thermal emittance. Economic considerations demand the use of thin films, rather than bulk materials. The thin film reflector must be capable of withstanding high temperatures of operation. Compatibility of the reflector with the substrate below, and the absorber above, is required for long-time service. Highly reflective silver films suffer reflectance losses by agglomeration, and …

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Radiobiological Aspects Of Supralinear Photographic Emulsions, Robert Katz, Edward C. Pennington Nov 1978

Radiobiological Aspects Of Supralinear Photographic Emulsions, Robert Katz, Edward C. Pennington

Robert Katz Publications

Abstract Nuclear emulsions of the Ilford K series, exposed to X-rays from 15 to 150 kVp and systematically underdeveloped, exhibit supralinear blackness-exposure curves ranging from 1- to 4-hit in character, and whose shape is the same at all excitation voltages. Processing can be so adjusted that the curve shape is well represented by the model, and matches an experimental dose-response curve obtained with hamster cells after irradiation with gamma rays. The effective grain size of these emulsions is 1.3 μm when normalized to unit density material for comparison with the radiation-sensitive elements of biological cells. With fractionated exposures, response …

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Consequences Of Light Reflection At The Interface Between Two Transparent Media Such That The Angle Of Refraction Is 45°, R. M.A. Azzam Nov 1978

Consequences Of Light Reflection At The Interface Between Two Transparent Media Such That The Angle Of Refraction Is 45°, R. M.A. Azzam

Electrical Engineering Faculty Publications

The reflection of light at the interface between two transparent, homogeneous and optically isotropic media such that the angle of refraction is 45° has the following interesting consequences: (i) the interface relfectivity for the parallel (p) polarization is the square of that for the perpendicular (s) polarization; (ii) the angular deviation of the propagation direction upon refraction is equal to the polarization (or ellipsometric) angle ψ and (iii) the complex reflection coefficient for the ppolarization is stationary, in both magnitude and phase, with respect to small charges of the (refractive and/or absorptive) optical properties of …

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Two-Nucleon Transfer To T-Mixed States In ¹⁶O, H. T. Fortune, R. Middleton, Oleksa-Myron Bilaniuk Oct 1978

Two-Nucleon Transfer To T-Mixed States In ¹⁶O, H. T. Fortune, R. Middleton, Oleksa-Myron Bilaniuk

Physics & Astronomy Faculty Works

In a comparison of the reactions ¹⁴N(t, p) to the g.s. quadruplet of ¹⁶N and ¹⁴N(³He, p) to the dominantly T=1 analogs in ¹⁶O, only the 2⁻ levels have the expected cross-section ratio: σ(³He, p) over σ(t, p)=0.5. The cross sections for O⁻ and 3⁻ levels of 16O are reduced by a further factor of 2. Direct-reaction calculations are unable to reproduce the results. NUCLEAR REACTIONS ¹⁴N(t, p), ¹⁴N(³He, p), E=15.0 MeV; measured σ(Eₚ, θ). T mixing effect on reaction mechanism.

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Mobility Of Α Particles In Helium, J. M. Wadehra, James S. Cohen, J. N. Bardsley Sep 1978

Mobility Of Α Particles In Helium, J. M. Wadehra, James S. Cohen, J. N. Bardsley

Physics and Astronomy Faculty Research Publications

The mobility of α particles in helium gas is calculated using the zeroth-order Viehland-Mason theory with interaction potentials recently computed by Cohen and Bardsley. The results show a dependence on field strength similar to the measurements of Johnsen and Biondi but are lower in magnitude by about 5%.

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Higher Education Learning Project (Physics) Books, Robert Fuller Sep 1978

Higher Education Learning Project (Physics) Books, Robert Fuller

Robert G. Fuller Publications

The books in this small collection of paperbacks deal with many of the issues confronting physicists who teach undergraduates. These books are the result of several physicist- years of studying various aspects of teaching in undergraduate physics programs in the United Kingdom. Each book includes references to related books and articles.

I think that these books make an essential contribution to the literature about teaching physics at the university level. For too long many of the physics departments that I know have acted as if the only way to evaluate teaching was to give a multiple-choice questionnaire to students at …

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High Let Constraints On Low Let Survival, Robert Katz Sep 1978

High Let Constraints On Low Let Survival, Robert Katz

Robert Katz Publications

Survival curves for biological cells irradiated with gamma rays (and other low LET radiations) cannot be properly interpreted without examining the implications of these interpretations for high LET radiations. The theory of RBE demands that the RBE of any high LET radiation field is at most one when the probability for cell killing as a function of the absorbed dose of gamma rays is linear or sublinear, for homogeneous samples whose radiosensitivity parameters are not altered during the irradiation. A contrary experimental finding strongly suggests that the experimental sample is heterogeneous. Violation of this constraint is not unusual where the …

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The Formation And Decomposition Of Nickel Carbide In Evaporated Nickel Films On Graphite, S. Sinharoy, L. L. Levenson Aug 1978

The Formation And Decomposition Of Nickel Carbide In Evaporated Nickel Films On Graphite, S. Sinharoy, L. L. Levenson

Physics Faculty Research & Creative Works

Auger electron spectroscopy and X-ray photoelectron spectroscopy were used to study nickel carbide (Ni3C) formed during the evaporation of nickel onto the surface of single-crystal graphite. It is shown that Ni3C formed in this manner extends from the surface to close to the interface. A model is proposed to explain the mechanism of Ni3C formation. The 1s photoelectron peak from Ni3C is observed to have a binding energy 0.6 eV lower than that of pure graphite. This is attributed to the lack of any significant ionic bonding in Ni3C. © 1978.

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20th Annual Rocky Mountain Conference On Analytical Chemistry Aug 1978

20th Annual Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Abstracts and program from the 20th annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-sponsored by the Rocky Mountain Section of the Society for Applied Spectroscopy and the Rocky Mountain Chromatography Discussion Group. Held in Denver, Colorado, August 7-9, 1978.

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Esr And Spin-Lattice Relaxation Of Nd3+ In A Metallic Host: Larh2, S. A, Dodds, Jeff Sanny, R. Orbach Aug 1978

Esr And Spin-Lattice Relaxation Of Nd3+ In A Metallic Host: Larh2, S. A, Dodds, Jeff Sanny, R. Orbach

Physics Faculty Works

We report the first ESR observation of Nd3+ in a metal: cubic LaRh2. The resonance arises from a Γ6 ground state and exhibits hyperfine splitting at low temperature, allowing for positive identification. Above about 12 K, the ESR linewidth increases exponentially with temperature. We attribute this increase to the resonance phonon relaxation process involving the first excited state at 125±10 K.

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Effect Of Random Anisotropy On Magnetic Properties Of Amorphous Systems, J.D. Patterson, G.R. Gruzalski, David J. Sellmyer Aug 1978

Effect Of Random Anisotropy On Magnetic Properties Of Amorphous Systems, J.D. Patterson, G.R. Gruzalski, David J. Sellmyer

David Sellmyer Publications

We consider the random anisotropy model for amorphous magnetism by making a local-mean-field approximation (LMFA) on arrays of spin-one particles. Hysteresis loops and the temperature (T) dependence of several thermodynamic quantities are presented for various values of the ratio of the strength of the exchange (J) to the strength of the uniaxial anisotropy (D). Using the LMFA limits us to systems with a small number (N) of spins, of which we explicitly consider N=64, 216, and 1000. We assume periodic boundary conditions on a system with N1/3 spins along …

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Application Of An Extremum Principle To The Variational Determination Of The Generalized Oscillator Strengths Of Helium, J. M. Wadehra, Larry Spruch, Robin Shakeshaft Aug 1978

Application Of An Extremum Principle To The Variational Determination Of The Generalized Oscillator Strengths Of Helium, J. M. Wadehra, Larry Spruch, Robin Shakeshaft

Physics and Astronomy Faculty Research Publications

Variational principles have been used extensively for estimating some given functional F(φ, φ†) where the functions φ and φ† are well defined by a set of differential equations and boundary conditions but cannot be determined exactly. The variational principle for the estimation of a matrix element of an arbitrary Hermitian operator W involves not only the trial wave functions φt but also trial auxiliary Lagrange functions Lt; the Lt depend on the φt and on W. To determine the parameters in the Lt efficiently, a functional M …

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An Assessment Of The Transmission Electron Microscope For The Study Of Aerosol-Gas Interactions: Direct Observations Of Sodium Chloride Hydration Phenomena, Antony David Clarke Aug 1978

An Assessment Of The Transmission Electron Microscope For The Study Of Aerosol-Gas Interactions: Direct Observations Of Sodium Chloride Hydration Phenomena, Antony David Clarke

Dissertations and Theses

An experimental study of solid-gas interactions was made for sodium chloride particles, using a specially fabricated environmental chamber in a transmission electron microscope. It was found that under suitable conditions the hydration and dehydration of these particles could be directly observed and quantitatively measured. Measurements of growth were obtained with a time resolution of one-thirtieth of a second for particles having diameters ranging from 0.02 μm to 1.0 μm.

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Graphical Approach To The Spin-Orbit Interaction, Keh-Ning Huang , Anthony F. Starace Aug 1978

Graphical Approach To The Spin-Orbit Interaction, Keh-Ning Huang , Anthony F. Starace

Anthony F. Starace Publications

We derive a new form for the matrix element of the two-particle mutual spin-orbit interaction in the Breit-Pauli approximation. The complexity of standard tensor-operator expansion techniques is obviated by suitably decomposing the mutual spin-orbit interaction into products of spin and orbital angular-momentum operators, whose matrix elements in the lmisms scheme are obtained in a straightforward manner. Graphical representations are given for both the one- and two-particle spin-orbit interactions, thereby permitting the analytical evaluation by graphical techniques of the spin-orbit interaction between arbitrary configurations in any coupling scheme. The graphical procedure for evaluating these matrix elements is demonstrated …

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Ionization Studies Of Nitrogen & Nitrogen-Sulfur Hexaflouride Mixtures, Amir Fallahi Aug 1978

Ionization Studies Of Nitrogen & Nitrogen-Sulfur Hexaflouride Mixtures, Amir Fallahi

Masters Theses & Specialist Projects

Ionization measurements as a function of concentration and pressure have been made in nitrogen and nitrogen-sulfur hexafluoride gas mixtures containing either cyclopropane, ethylene, propylene, acetylene, ethane, or impurity. These studies have been made to understanding of the gas kinetics involved propane as contribute in nitrogen an to the and nitrogen-sulfur hexafluoride laser systems. Impurity gases were chosen on the basis of their ionization potentials relative to the C3πu state in nitrogen that is responsible for the lasing action. Analysis of the data indicated that a Jesse effect exists for those impurity gases whose ionization potentials lie below …

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Representation Of Ab Initio Energy Surfaces By Analytic Functions, R.L. Vance, Gordon A. Gallup Jul 1978

Representation Of Ab Initio Energy Surfaces By Analytic Functions, R.L. Vance, Gordon A. Gallup

Gordon Gallup Publications

A method for the analytical representation of ab initio energy surface results is described. For a three-atom surface, the potential function is written as a sum of atomic, two-body, and three-body terms. This allows an easy fitting of the whole surface, including the dissociated and united atom limits. The theory is applied to an H3 surface of limited accuracy calculated for these purposes. Comparisons are made, where possible, with more accurate calculations. Extensions to surfaces involving four or more atoms are also discussed.

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Angular Differential Cross Sections For 25-, 50-, And 100-Kev-Proton Excitation Of Helium To The N=2 Level, John T. Park, Jacob M. George, Jerry Peacher, Judith E. Aldag Jul 1978

Angular Differential Cross Sections For 25-, 50-, And 100-Kev-Proton Excitation Of Helium To The N=2 Level, John T. Park, Jacob M. George, Jerry Peacher, Judith E. Aldag

Physics Faculty Research & Creative Works

Differential cross sections for 25-, 50-, and 100-keV-proton excitation of helium to the n=2 level have been determined for center-of-mass scattering angles from 0 to 1.2 mrad. The cross sections were obtained from an analysis of the angular distribution of the scattered protons which had lost an energy corresponding to the excitation of the helium target to its n=2 level. The differential cross section is very sharply peaked in the forward direction and decreases by a factor of 45 in 1.0 mrad at 25 keV and by a factor of 650 in 1.0 mrad at 100 keV. The data are …

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Measurements Of Orbit-Lattice Coupling Of Er And Dy Impurities In Ag And Al Hosts, S. A. Dodds, Jeff Sanny Jul 1978

Measurements Of Orbit-Lattice Coupling Of Er And Dy Impurities In Ag And Al Hosts, S. A. Dodds, Jeff Sanny

Physics Faculty Works

The magnetic resonance of dilute Dy and Er impurities has been observed in thin polycrystalline Al and Ag films on two different substrates. The films are deposited at room temperature, and the measurements are made at liquid-helium temperatures. During cooling, the difference in thermal contraction between film and substrate produces an effectively uniaxial strain in the film. This results in an anisotropic g value, which we have used to obtain lower limits on the orbit-lattice coupling coefficient for these systems. We find values for V ( Γ 3g, 2 ) from 600 to 2000 cm − 1 , somewhat …

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