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Full-Text Articles in Physics
Electron Detachment In Negative-Ion Collisions. Iii. Model Calculations., T. S. Wang, John B. Delos
Electron Detachment In Negative-Ion Collisions. Iii. Model Calculations., T. S. Wang, John B. Delos
Arts & Sciences Articles
With the use of a previously developed close-coupling theory, and simple models for the energy gap and propagator that arise in that theory, calculations are made of the properties of the survival probability for the negative ions and of the energy spectrum of detached electrons. Special attention is given to interference effects that might be seen under favorable circumstances.
Bound State Semiclassical Wave Functions, Stephen Knudson, John B. Delos, D. W. Noid
Bound State Semiclassical Wave Functions, Stephen Knudson, John B. Delos, D. W. Noid
Arts & Sciences Articles
The semiclassical theory developed by Maslov and Fedoriuk is used to calculate the wave function for a two‐dimensional bound state system. We investigate in detail an eigenstate of a coupled anharmonic oscillator system. The primitive semiclassical wave function is obtained from the characteristic function S and the density function J. Each of these functions consists of four branches corresponding to the four possible directions of motion of the classical trajectory through any point. The interference from the four branches determines the basic structure of the wave function. A uniform approximation gives a wave function which is well behaved along …
Probability Conservation In Theories Of Collisional Ionization And Detachment, M. L. Du, John B. Delos
Probability Conservation In Theories Of Collisional Ionization And Detachment, M. L. Du, John B. Delos
Arts & Sciences Articles
The semiclassical local-complex-potential theory has been widely used to describe detachment and ionization in atom-atom and ion-atom collisions. However, it has been shown that the resulting formulas do not conserve probability. In this paper, we show that the problem arises from the inconsistent treatment of the effects of interference, tunneling, and diffraction. A more complete theory is based upon the close-coupling expansion, which leads to an infinite set of coupled equations. A method for solving such sets of equations was developed in earlier work. Here we implement that method using a new iterative numerical scheme, and we show that the …
Effect Of Strain On Muon Diffusion And Trapping In Metal By Bassam Salim Hitti, Bassam Salim Hitti
Effect Of Strain On Muon Diffusion And Trapping In Metal By Bassam Salim Hitti, Bassam Salim Hitti
Dissertations, Theses, and Masters Projects
Positive muons implanted in metal distort the surrounding lattice; therefore, in addition to electronic interactions, the elastic forces have to be considered in determining the muon state. to explore the elastic and electronic diffusion and trapping mechanisms, we studied AlCu(,420ppm), AlMg(,1000ppm) and AlAg(,1000ppm) alloys. These alloys were selected for the different effects on the host lattice of these impurities; Cu contracts the Al lattice, Mg expands it and Ag has nearly no effect. On the other hand Cu and Ag are monovalent while Mg is divalent. For AlCu between 5K and 14K the temperature exponent (beta) of the two-state-model trapping …
Determination Of The Vacancy Migration Energy Of Aluminum By Nmr, Terry William Gullion
Determination Of The Vacancy Migration Energy Of Aluminum By Nmr, Terry William Gullion
Dissertations, Theses, and Masters Projects
Monovacancy diffusion is a thermally activated process characterized by an activation energy E(,d). The diffusion of atoms requires the formation and migration of vacancies. The concentration of vacancies n/N is given by n/N (DBLTURN) exp(-E(,f)/kT). It can be shown that the activation energy E(,d) is the sum of the energy to form a vacancy E(,f) and the energy required for an atomic jump E(,m): E(,d) = E(,f) + E(,m). Furthermore, the atomic jump rate (omega)(,j) can be shown to be thermally activated and given by (omega)(,j) (DBLTURN) (nu)(,o)(n/N)exp(-E(,m)/kT) ((nu)(,o) is the attempt frequency).;NMR offers many techniques to measure the activation …
Rydberg Atoms In Parallel Electric And Magnetic Fields, Robert Leonard Waterland
Rydberg Atoms In Parallel Electric And Magnetic Fields, Robert Leonard Waterland
Dissertations, Theses, and Masters Projects
I have calculated the energy spectrum of a highly excited atom which lies in parallel, static electric and magnetic fields. In parallel fields the Coulomb quantum numbers n and m are still "good" quantum numbers but 1 is not: the calculation is for n = 30, m = 1 atoms.;The eigenvalues were obtained by semi-classical quantisation of first-order classical perturbation theory and have been calculated for a large range of electric and magnetic field strengths. The results are in good agreement with those found from first-order degenerate quantum perturbation theory.;The semi-classical analysis provides a correlation diagram connecting the Stark effect …
Low-Energy Collisions Of Alkali-Metal Anions, David M. Scott
Low-Energy Collisions Of Alkali-Metal Anions, David M. Scott
Dissertations, Theses, and Masters Projects
Measurements of the total cross section for electron detachment, (sigma)(,e)(E), are presented for low-energy (E(,1ab) < 300 eV) collisions of Na('-), K('-), and Cs('-) with atomic and molecular targets. For many of the atomic (rare-gas) targets, the energy dependence of (sigma)(,e)(E) is striking: virtually no detachment is observed until relatively high collision energies (50 eV in the center-of-mass frame) are reached, in contradistinction to what has been observed for similar collisions involving H('-). The thresholds for alkali anion detachment are approximately equal to the thresholds for excitation observed in collisions of neutral alkali atoms with these same targets. The similarity between the dynamics of the neutral system and that of the negative ion system, together with the observation (at greater energies) of detachment accompanied by excitation of the alkali parent, suggests that electron detachment may be mediated by a two-electron process in some cases. A simple curve-crossing mechanism adequately reproduces the observed (sigma)(,e)(E) for several of these rare-gas targets.;Measurements of both (sigma)(,e)(E) and the cross section for charge transfer (sigma)(,i)(E) have also been completed for H(,2), D(,2), N(,2), O(,2), CO, CO(,2), SO(,2), N(,2)O, CH(,4), and SF(,6) targets. Electron detachment is the dominant process for all of these targets except O(,2), SO(,2), and SF(,6), with thresholds on the order of a few eV. Structure in (sigma)(,e)(E) for the CO(,2) target has been attributed to charge transfer to a metastable state of CO(,2)('-)(('2)A(,1)). Similarly, in the case of N(,2)O, both (sigma)(,e)(E) and (sigma)(,i)(E) exhibit behavior which suggests that a temporary negative ion state is formed during the collision. In the case of the O(,2), SO(,2), and SF(,6) targets, charge transfer is observed to have particularly large cross sections (>100 (ANGSTROM)('2)) at low collision energies.
A Nuclear Magnetic Resonance Study Of Deuterated Poly(Vinylidene Fluoride) And A Copolymer Of Deuterated Vinylidene Fluoride And Tetrafluoroethylene, Montee A. Doverspike
A Nuclear Magnetic Resonance Study Of Deuterated Poly(Vinylidene Fluoride) And A Copolymer Of Deuterated Vinylidene Fluoride And Tetrafluoroethylene, Montee A. Doverspike
Dissertations, Theses, and Masters Projects
Pulsed deuterium NMR experiments have been performed on deuterated samples of poly(vinylidene fluoride), PVF(,2), repeat unit CH(,2)CF(,2) and the copolymer poly(vinylidene fluoride)-tetrafluoroethylene (80-20), (PVF(,2)-F(,4)E). A deuterium line shape study has been employed to characterize the orientational distribution of the dipole moments in both poled and unpoled samples. In addition, the orientational distributions of chain axis alignment has been measured in stretched samples.;PVF(,2) and PVF(,2)-F(,4)E exhibit unique piezoelectric and pyroelectric properties which are due to their crystalline components (approximately 50% in typical material). Four crystalline phases exist in the homopolymer PVF(,2), the (alpha), (beta), (gamma), and the (delta). The relatively electrically …