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Full-Text Articles in Physics
Effect Of Closed Classical Orbits On Quantum Spectra: Ionization Of Atoms In A Magnetic Field. I. Physical Picture And Calculations, M. L. Du, John B. Delos
Effect Of Closed Classical Orbits On Quantum Spectra: Ionization Of Atoms In A Magnetic Field. I. Physical Picture And Calculations, M. L. Du, John B. Delos
Arts & Sciences Articles
This is the first of two papers that develop the theory of oscillatory spectra. When an atom is placed in a magnetic field, and the absorption spectrum into states close to the ionization threshold is measured at finite resolution, so that individual energy levels are not resolved, it is found that the absorption as a function of energy is a superposition of sinusoidal oscillations. These papers present a quantitative theory of this phenomenon. In this first paper, we describe the physical ideas underlying the theory in the simplest possible way, and we present our first calculations based upon the theory. …
Effect Of Closed Classical Orbits On Quantum Spectra: Ionization Of Atoms In A Magnetic Field. Ii. Derivation Of Formulas, M. L. Du, John B. Delos
Effect Of Closed Classical Orbits On Quantum Spectra: Ionization Of Atoms In A Magnetic Field. Ii. Derivation Of Formulas, M. L. Du, John B. Delos
Arts & Sciences Articles
A formula is derived for oscillations in the near-threshold absorption spectrum of an atom in a magnetic field. Three approximations are used. (1) Near the atomic nucleus, the diamagnetic field is negligible. (2) Far from the nucleus, the waves propagate semiclassically. (3) Returning waves are similar to (cylindrically modified) Coulomb-scattering waves. With use of these approximations, together with the physical picture described in the accompanying paper, an algorithm is specified for calculation of the spectrum.
Atomic Electrons In Strong Magnetic Fields: Transition From Elliptical To Helical Behavior., John B. Delos, Stephen Knudson, Shena Sikora, Robert Leonard Waterland, S. Whitworth
Atomic Electrons In Strong Magnetic Fields: Transition From Elliptical To Helical Behavior., John B. Delos, Stephen Knudson, Shena Sikora, Robert Leonard Waterland, S. Whitworth
Arts & Sciences Articles
The behavior of an atomic electron in a static magnetic field strong enough to correspond to the transition regime is examined. The field strength is characterized by the parameter L^, the effective component of angular momentum. A Floquet-Mathieu analysis shows that the bifurcation of classical trajectories into elliptical and helical families is related to the 2:1 resonance which occurs at L^=L^T. Quantum mechanics gives an avoided crossing at L^T; we examine the nature of the wave functions as L^ passes through the resonance. Semiclassical calculations accurately reproduce the quantum eigenvalues and produce trajectories which underlie the quantum wave functions. …
Laser-Induced Collisional Detachment, D. Luo, John B. Delos, S. Geltman
Laser-Induced Collisional Detachment, D. Luo, John B. Delos, S. Geltman
Arts & Sciences Articles
A theoretical study is presented of the process of photodetachment of a negative ion by sub-threshold-frequency radiation in the presence of a simultaneous collision. Calculations are carried out for the H−-He case and the resulting cross section is compared with other competing processes, such as two-photon photodetachment and nonradiative collisional detachment.
Semiclassical Interpretation Of Eigenvectors For Excited Atoms In External Fields, Robert Leonard Waterland, M. L. Du, John B. Delos
Semiclassical Interpretation Of Eigenvectors For Excited Atoms In External Fields, Robert Leonard Waterland, M. L. Du, John B. Delos
Arts & Sciences Articles
Eigenvectors for an electron in an atom in parallel electric and magnetic fields are calculated, and a semiclassical interpretation of their behavior is obtained. Eigenvectors can in this case be regarded as ‘‘wave functions in angular momentum space.’’ The matrix equation defining the eigenvectors is written as a difference equation, and then converted to a pseudodifferential equation; a systematic procedure is then used to construct a semiclassical approximation. It is found that the same classical Hamiltonian that has been previously used to calculate semiclassical eigenvalues provides a WKB-type representation of the eigenvectors. The development sheds new light on action-angle formulations …
The Measurement Of Strong Interaction Effects In High-Z Sigma Hyperonic Atoms, William Clarke Phillips
The Measurement Of Strong Interaction Effects In High-Z Sigma Hyperonic Atoms, William Clarke Phillips
Dissertations, Theses, and Masters Projects
Strong-interaction effects have been observed in the X-ray spectra of atoms formed with {dollar}\Sigma\sp-{dollar} in lead and tungsten.;In the experiment, performed at the Alternating Gradient Synchrotron of Brookhaven National Laboratory, negative kaons were brought to rest in a novel laminar target consisting of thin sheets of high-Z material in a liquid hydrogen bath. The geometry of the target was designed to optimize the production of high-Z {dollar}\Sigma\sp-{dollar} atoms and the detection of their subsequent de-excitation X rays. A method of identifying the energetic {dollar}\pi\sp+{dollar} from the production reaction K{dollar}\sp-{dollar}+ p {dollar}\to\Sigma\sp- +\pi\sp+{dollar} resulted in a factor of 15 improvement in …
Statistically Constrained Decimation Of A Turbulence Model, Timothy Joe Williams
Statistically Constrained Decimation Of A Turbulence Model, Timothy Joe Williams
Dissertations, Theses, and Masters Projects
The constrained decimation scheme (CDS) is applied to a turbulence model. The CDS is a statistical turbulence theory formulated in 1985 by Robert Kraichnan; it seeks to correctly describe the statistical behavior of a system using only a small sample of the actual dynamics. The full set of dynamical quantities is partitioned into groups, within each of which the statistical properties must be uniform. Each statistical symmetry group is then decimated down to a small sample set of explicit dynamics. The statistical effects of the implicit dynamics outside the sample set are modelled by stochastic forces.;These forces are not totally …