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Increasing The Efficiency Of A Surface Ionization Mass Spectrometer, Thomas Curtis Adams

Physics & Astronomy ETDs

An Avco surface ionization mass spectrometer (model 90,000) was installed at the Los Alamos Scientific Laboratory in February, 1968. Since that date this machine has been used as a production instrument for the isotopic analysis of uranium and plutonium samples. During 1969, it was realized that a problem inherent in the ionization mechanism of the instrument was degrading the accuracy of results, and that the number of man-hours expended in reducing data had become excessive. As soon as this situation became apparent, corrective action was initiated to reduce the effect of the ionization problem and to decrease the amount of …

Calculation Of Point-Defect Energies And Displacements In Alkali Halides Using The Lattice-Statics Method, Arnold Karo, John R. Hardy

John R. Hardy Papers

The method of lattice statics, in the zero-order approximation, is used to evaluate the Schottky-pair formation energies and the displacement fields about positive- and negative-ion vacancies for all alkali halide crystals with rock-salt structures. The deformation-dipole model, used extensively in earlier work on the lattice dynamics of these crystals, is employed to describe the host lattice. Long-range Coulomb interactions are included explicitly, and short-range repulsive interactions are described by a simple Born-Mayer potential. Comparison is made with earlier Mott-Littleton-type calculations and very satisfactory agreement is found. Comparison with available experimental values is somewhat less satisfactory, particularly regarding the lithium salts; …

Length And Velocity Formulas In Approximate Oscillator-Strength Calculations, Anthony F. Starace

Anthony F. Starace Publications

The matrix element for electric dipole transitions is correctly given by the length formula in the Hartree-Fock, configuration-interaction, and related approximations, which involve the diagonalization of an approximate, but nonlocal, Hamiltonian.

An Experimental Investigation Of The Vortex Sink Rate Sensors, Nelson L. Lu

Mechanical & Aerospace Engineering Theses & Dissertations

The vortex sink rate sensor device consists basically of an ideal sink flow between two coaxial disks. A sink tube was located at the center of one disk. The vortex was created by the rotation of the unit about its axis of symmetry. Five inch and 10 inch diameter of porous couplers were used for the air chamber here in this investigation. Several slenderness parameters, i.e., the ratio of the sink tube diameter to the height of the air chamber ^ro/n were conducted. Two probes were used to measure the static pressure and stagnation pressure respectively at various positions …

Track Theory And Radiation Quality, Robert Katz

Robert Katz Publications

Radiation detection and damage data from several physical, chemical, and biological systems have been analyzed by a unified track theory, in which observed effects are attributed to the interaction of secondary electrons with the medium. Gamma-ray dose-response curves are combined with calculations of the spatial dose distribution about an ion's path to yield dose-response curves (survival curves) for heavy ion bombardment, through appropriately defined parameters. Perplexing phenomena associated with high LET radiation are sorted out according to track regime (grain-count or track-width), inactivation mode (gamma-kill or ion-kill), structural complexity (elementary, cellular, multicellular), and end-point. The central problem in assigning a …

Lamb-Mössbauer Factor Of Sodium Ferrocyanide, Daniel L. Decker, L. E. Lortz

Faculty Publications

Using a set of commercially prepared sodium ferrocyanide absorbers enriched to 91.2% Fe57 the Lamb-Mössbauer factor was measured to be 0.28±0.03. The thickness of Fe57 for these absorbers was measured using x-ray absorption techniques and was found to be considerably smaller than that advertised by the manufacturer even after correcting for the size of the ferrocyanide particles in the absorbers.

Dielectric Polarization And Alignment And The Structure Of Polar Fluids, John D. Ramshaw, D. W. Schaefer, John S. Waugh, J. M. Deutsch

Physics Faculty Publications and Presentations

An analysis is made of the information about the structure of dense polar fluids which resides in the dielectric constant, the Kerr constant, and the nuclear magnetic resonance (NMR) quadratic electric field effect. The inadequacy of the "local-field" model for liquids is discussed. The existence of a nonzero molecular hyperpolarizability is shown to destroy an equivalence which would otherwise exist between the Kerr and NMR experiments, and can easily account for apparent discrepancies between the reported Kerr and NMR data for nitrobenzene and nitromethane. A method is presented for removing dielectric boundary effects from statistical averages, so that the averages …

A Vibrational And Rotational Analysis Of Eight Simple Models Of The Hydrogen Molecule In The Ground State., Stuart Fleming Hayes

Physics & Astronomy ETDs

The object of this dissertation was the investigation of the influence on the delta G curve for H2 of polarization, enhancement of charge between the nuclei, and variation of the screening parameter. A better understanding of the influence of these factors could lead to progress in estimating more accurately the dissociation energies of diatomic molecules. Also to be investigated was the correlation between these factors and the vibrational and rotational spectroscopic constants, particularly Bv.

The Heitler-London combination of atomic orbitals (referred to as phi 1) was used in every wave function The atomic orbital 2pz was used in phi 2 …

Observation Of Quadrupole Splitting Of B-12 In A Single Crystal, R. L. Williams Jr., Richard C. Haskell, Leon Madansky

All HMC Faculty Publications and Research

The quadrupole coupling of B-12 implanted in Be-9 has been observed using a single crystal of Be. One sees a narrow resonance line, the location of which depends in the normal way on the orientation of the crystalline c-axis with respect to the external magnetic field direction. The coupling constant is given by e2qQ/h = 54.9(6) kHz. This is consistent with our previous measurement using a Be foil. Using the field gradient at Be-9 lattice sites, calculated by Pomerantz and Das, one finds Q(B-12) = about 34.6 mb.

Angular And Energy Distribution Of Cross Sections For Electron Production By 50-300-Kev-Proton Impacts On N2, O2, Ne, And Ar, J. B. Crooks, M. Eugene Rudd

M. Eugene Rudd Publications

Cross sections differential in angle and ejection energy for electron production by proton impact on nitrogen, oxygen, neon, and argon have been measured using electrostatic analysis and counting of individual electrons. The range of proton energies was 50-300 keV, the angles ranged from 10° to 160°, and the electron energies were measured from 1.5 to 1057 eV. Integrations over angle and/or electron energy yielded singly differential and total electron production cross sections. Our total cross sections for oxygen fall halfway between previous data of deHeer et al. and Hooper et al., but our argon cross sections agree better with deHeer …

Measurement Of Nuclear Magnetic Dipole Moment Of Li-8 By Implantation In Metal Foils, Richard C. Haskell, R. L. Williams Jr., Leon Madansky

All HMC Faculty Publications and Research

Polarized 8Li nuclei have been produced through the 7Li(d,p) reaction using the 3.5-MeV Van de Graaff accelerator at Brookhaven National Laboratory. The observed polarization was a slowly-varying function of deuteron energy over the range 1.3-2.9 MeV, reaching a maximum of about +1.6%. The recoiling nuclei were stopped in Au, Pt and Pd foils and the effective dipole moments were measured by a resonant depolarization method. The results were 1.65362(22)µN, 1.65288(20)µN and 1.65270(30)µN respectively. These are consistent with the work of Connor, who found µ(8Li) =1.6530(8)µN in a LiF crystal. An upper limit for the 8Li quadrupole moment will also be …

Experimental And Theoretical Study Of The Sign Preference In The Nucleation Of Water Vapor, Daniel R. White, James L. Kassner

Physics Faculty Research & Creative Works

The nucleation of water vapor on ions in atmospheres of helium and argon was studied using an expansion type cloud chamber. Separation of the positive and negative ions was achieved so that the nucleation could be studied as a function of both the sign of the ionic charge and the supersaturation. A semiphenominological theory was developed as an extension of the classical liquid drop theory to include the effects of the ionic charge on the nucleation process. The theoretical model of the prenucleation embryo was assumed to possess an oriented dipole surface layer with the direction of orientation dependent on …

Excitation Of The 2s State Of Atomic Hydrogen By Electron Impact In The Distorted-Wave Approximation - Angular Distributions, W. Neil Shelton, E. S. Leherissey, Don H. Madison

Physics Faculty Research & Creative Works

The excitation of ground-state hydrogen atoms to the 2s state by the impact of electrons with energies of 1 to 50 Ry (13.6 to 680.3 eV) has been calculated in the distorted-wave approximation with exchange included. The angular distributions of the scattered electrons at 1 and 4 Ry are compared with those derived from the close-coupling calculations by Burke, Schey, and Smith, and are compared with four different plane-wave theories at all energies calculated. Taking the close-coupling results as a standard, it is found that the distorted-wave angular distributions represent an improvement over those of the plane-wave theories.

Calculation Of Anisotropic Hyperfine Constants For Lattice Nuclei Near A Shallow Donor, Edward B. (Boyd) Hale, Robert Lee Mieher

Physics Faculty Research & Creative Works

A method is presented for calculating the magnetic anisotropic (dipolar) hyperfine constants for lattice nuclei near a shallow-donor impurity. The method assumes that the wave function of the donor electron can be expressed in an effective-mass form, i.e., a slowly varying envelope function times conduction-band Bloch functions. For each dipolar hyperfine constant, two separate calculations are performed. One calculation is for a local region about the lattice nucleus of interest. The greatest part of the interaction occurs in this region (about 85 ± 10%). The second calculation is for the more distant region. The dipolar constants in the distant region …

MöSsbauer Studies Of Stable Interstitial And Substitutional Sites Of Cobalt In Gold, Charles Freeland Steen

Dissertations and Theses

Precision measurements of the Debye-Waller factor of Fe⁵⁷ in Au using the wide black absorber technique have been made in the temperature range from room temperature to 830 K. The major source of error arises from Au L_y x-rays which are unresolved by the radiation detection system from the 14.4 KeV gamma ray. The K absorption edge of Br has been used to correct for the presence of x-rays.

These measurements have revealed the existence of two nonequivalent lattice sites which the Co⁵⁷ impurity (parent of Fe⁵⁷) may occupy. One of the sites has been …

Local Magnetic Moments And The Mossbauer Effect, Richard B. Frankel, Brian B. Schwartz

Physics

No abstract provided.

Absolute Cross Sections For Excitation Of Neon By Impact Of 20-180 Kev H , H₂ And He Ions, George William York

Doctoral Dissertations

"The technique of heavy-ion energy-loss spectrometry has been used to measure excitation cross sections for the (2p⁵)3s and (2p⁵)3p electronic configurations of Neon. The incident particles used were H⁺ , H⁺₂ and He⁺ at impact energies from 20-180 keV. The results are compared with previous optical measurements of the emission cross sections of lines from these levels as excited by H⁺ and He⁺ impact. Agreement is not good, either in shape or in absolute magnitude for excitation of the (2p⁵)3s configuration. However, agreement is surprisingly good for excitation of the (2p⁵)3p configuration. A curve fitting technique has been applied to …

X-Ray And Mössbauer Spectroscopy Studies Of The Silicon-Antimony And Bismuth-Antimony Alloys, James Ralph Teague

Doctoral Dissertations

"X-ray and Mossbauer spectroscopy were used to investigate two antimony alloys, Bi-Sb and Si-Sb, showing semiconductorsemimetallic transitions or vice versa, depending on the antimony concentration in the host lattice. Resistivity and density measurements were found to be helpful in the analysis of the results. X-ray studies for dislocation-free antimony-doped silicon showed that the lattice constant of the alloy increased as the antimony concentration increased from 10¹⁸ to 10¹⁹ Sb atoms/cc. Rather good agreement was found between theoretical and experimental changes in lattice constant for dislocation-free silicon. Mössbauer studies showed that the isomer shift decreased linearly with increasing antimony concentration, which …

Theory Of Nucleation Of Water Properties Of Some Clathrate Like Cluster Structures, Mehdi Daee

Doctoral Dissertations

"The tranquility of classical homogeneous nucleation theory has been disturbed by the introduction of statistical mechanical correction factors to a basically thermodynamic theory. These factors, which appear to be essential, destroy much of the agreement with experiment in the case of water vapor. A molecular model for the pre-nucleation water clusters is proposed with a view toward resolving some of these difficulties. As a first step, the Properties of a few specific cluster configurations have been examined. Clathrate-like structures containing 16 to 57 water molecules are discussed. The hydrogen bonds were treated as simple harmonic oscillators for the purpose of …

Homogeneous Nucleation Of Water Vapor In Inert Gas Atmospheres, Arthur Henry Biermann

Doctoral Dissertations

"The homogeneous nucleation of water vapor in atmospheres of helium, neon, argon, krypton, and xenon was studied using an expansion type cloud chamber. A strong dependence of the nucleation rate on the particular inert carrier gas was observed. At present the only dependence upon the nature of the carrier gas included in classical nucleation theories is a small factor arising from kinetic considerations which is in the wrong direction to explain the observations. To explain the dependence of the rate on the nature of the carrier gas, a molecular cluster model is assumed allowing inert gas atoms to occupy the …

Photoionization Of Photoexcited Cesium, Robert E. Hebner

Doctoral Dissertations

"A new method for obtaining the cross section for photoionization of photoexcited cesium is presented. The salient feature of this experiment is to use three crossed beams, i.e., two light beams intersecting a beam of cesium atoms. The cross section is determined by counting the ions produced by the two step process: Cs (6S) + h[upsilon]₁ --> Cs (6P) ; Cs (6P) + [upsilon]₂ --> Cs⁺ + e⁻ The relative cross section for the second step has been obtained from threshold (5060 Å) to 2500 Å. The excitation light source used in obtaining this cross section was a rf resonance …

Thermal Expansivity And Refractive Index Determinations For Some Hydrosol Systems And Their Similarity To Properties Ascribed To "Anomalous" Water, Gerald Wayne Chappue

Masters Theses

"The characteristic thermal expansion and refractive index of aqueous dispersions of SiO₂ and NaOH were determined for samples contained in quartz micro-capillaries. Comparison is made with the expansivity and refractive properties of anomalous water or polywater as reported by other investigators. The similarity between the properties and behavior of various hydrosol systems and those ascribed to anomalous water is cited as a serious challenge to the hypothesized existence of an allotropic modification of water"--Abstract, page ii.

Nuclear Orientation Of 253Es In Neodymium Ethylsulfate, A. J. Soinski, Richard B. Frankel, Q. O. Navarro, D. A. Shirley

Physics

Einsteinium-253 nuclei were oriented at low temperatures in a neodymium ethylsulfate lattice. From the temperature-dependent α-particle angular distribution a nuclear magnetic moment |μ|=(2.7±1.3)μ_N was deduced. From the values for the angular distribution function at the lowest temperatures it was possible to test the predictions of the Mang shell-model theory for the relative phases and amplitudes of the α-partial waves. As predicted, the waves of angular momentum L=0 and 2 are in phase, and the L=0 and 4 waves are out of phase. The predicted wave amplitudes are in error, especially that of the L …

Doppler Shift In Frequency In The Transport Of Electromagnetic Waves Through An Underdense Plasma, Jerry Peacher, Kenneth M. Watson

Physics Faculty Research & Creative Works

In an earlier publication, the validity of the radiation transport theory was studied for the calculation of multiple scattering of electromagnetic waves by a turbulent plasma. In the present paper, we extend the transport theory to include a description of the Doppler shift in frequency caused by electron motion.

De Haas-Van Alphen Effect In Dilute Beryllium-Copper Alloys , I.S. Goldstein, David J. Sellmyer, B.L. Averbach

David Sellmyer Publications

The de Haas-van Alphen effect was investigated in pure beryllium and in Be-Cu alloys containing up to 0.34 at.% Cu. The extremal cross-sectional areas of the cigar-shaped third-band electron pieces of Fermi surface decreased with alloying. The areas of the coronet-shaped second-band hole piece increased with alloying. The magnitude of the area changes were compared with rigid-band-theory predictions. Corrections for lattice-parameter changes were included when possible. In the low-concentration limit, the theory is able to account for the observed area changes. For the highest-concentration alloy, there are deviations, for all areas measured, to greater changes than are predicted by the …

Transient Optical Absorption By Self-Trapped Excitons In Alkali Halide Crystals, Robert Fuller, R.T. Williams, M.N. Kabler

Robert G. Fuller Publications

Transient absorption spectra produced by pulsed electron excitation at low temperature have been identified as due to transitions originating in the lowest triplet states of the self-trapped exciton. The current model, comprising an electron plus a self-trapped hole, is shown to provide electronic configurations for the higher excited states which give a good account of the principal features of the spectra.

12th Annual Rocky Mountain Spectroscopy Conference

Rocky Mountain Conference on Magnetic Resonance

Program and abstracts from the 12th annual meeting of the Rocky Mountain Spectroscopy Conference, sponsored by the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, August 3-4, 1970.

Small Angle Elastic Scattering Of 1.33 Mev Photons From Lead, Chwan-Kang Chiang

Masters Theses

No abstract provided.

Limited Resurrection Of The Born Approximation, Paul Finkler

Paul Finkler Papers

It is shown that the ordinary Born approximation for pn and pp̅ charge-exchange scattering correctly accounts for (1) the shape of the forward peak for 0 ≤ (-t) ≤ µ²/2 at P_L = 8 GeV/c, and (2) the energy dependence of the cross sections at t=0 in the energy range P_L,=2—8 GeV/c. This result is analogous to the well-known success of the electric Born approximation in Π⁺ photoproduction. It is then shown that the simplest interpretation of this surprising result within the framework of Regge-pole theory is in terms …

Hot Electron Injection Into Liquid Argon From A Tunnel Cathode, Pavel Smejtek, David G. Onn, M. Silver, P. Kumbhare

Physics Faculty Publications and Presentations

Hot electrons from a tunnel cathode have been injected into liquid argon (99.998% pure) at 87°K. The current vs voltage characteristics indicate that the injected hot electrons thermalize very slowly, losing their energy only by elastic scattering processes and finally by capture by the dilute impurities. The deduced thermalization time and distance are very long compared with that in helium, where bubble formation is responsible for energy loss.