Investigations of negative ion and electron emission from gas-covered metal surfaces due to the impact of low energy (30-300 eV) positive ions and, separately, photons (2-5 eV) are presented. In both cases, the negative ion formation process is thought to occur via electron tunneling from the surface or its substrate to a sputtered or photodesorbed neutral atom or molecule.;In particular, absolute total negative ion and electron yields for collisions of positive alkali ions with a gas-covered Mo substrate have been measured. Mass analysis of the sputtered negative ions show that O{dollar}\sb2\sp-{dollar} is the dominant ion at low impact energies. This coupled with the fact that threshold energies for observing secondary negative ions and electrons are the same suggests that electron production is correlated to the O{dollar}\sb2\sp-{dollar} production, and specifically that electrons are the result of autodetachment of excited O{dollar}\sb2\sp-{dollar}. This hypothesis provides an explanation of the mechanism responsible for the emission of electrons at low impact energies.;Relative yields for photodesorbed H{dollar}\sp-{dollar} from a barium substrate have been measured as a function of photon wavelength for the range of 245 to 585 nm. A description of the formation of H{dollar}\sp-{dollar} due to photodesorption of BaH on a surface is consistent with the known energetics of the system. An estimate of the absolute yield of photodesorbed H{dollar}\sp-{dollar} per incident photon has been made.

Measurements of the absorption spectrum of atomic H in strong magnetic fields have been analyzed. The measurements, performed by the Bielefeld, Germany experimental group, investigated the photoabsorption to levels near the ionization threshold in magnetic fields ranging from 2.7 to 6 Tesla. Taking advantage of a classical scaling law, the photon energy and the magnetic field strength were varied simultaneously in the experiment and the absorption rate vs. B{dollar}\sp{lcub}-1/3{rcub}{dollar} at fixed scaled-energy, {dollar}\varepsilon{dollar} = E/(B/B{dollar}\sb{lcub}\rm o{rcub})\sp{lcub}2/3{rcub}{dollar} was measured. The absorption rate was observed to exhibit sinusoidal fluctuations which we correlate with closed classical orbit of the electron. A Fourier transformation of this signal yields peaks which we interpret as "recurrence strengths" which depend upon the classical action of the closed orbit. Closed-orbit theory gives formulas for these recurrence strengths. as the scaled energy is increased, observed recurrences proliferate, consistent with the change from orderly to chaotic motion of the electron. Bifurcation theory provides organizing principles for understanding this proliferation and for interpreting the data. New "exotic" orbits suddenly appear "out of nowhere" through saddle-node bifurcations. The "main sequence" of orbits is produced from an orbit parallel to B through a sequence of pitchfork and period-doubling bifurcations. Other recurrences are created by period-tripling and higher-order bifurcations of existing orbits. These bifurcations can have generic structure, or sometimes the structures are modified by symmetries of the system. Focusing effects associated with these bifurcations cause some recurrences to be particularly strong.

An experiment was performed at the Paul Scherrer Institut (PSI) to establish the conditions for the metastability of the 2S-state of muonic neon. The muonic atoms were formed by stopping negative muons in the neon-filled target chamber of the PSI cyclotron trap. A pair of intrinsic germanium detectors were used in coincidence to search for the two photon decay of the 2S-state. Both energy and time information from two photon events were written to disk for off-line analysis. Data were accumulated for neon pressures of 40 and 400 Torr. The data were then searched for evidence of two photon transitions from the 2S-state.;The germanium detectors were sensitive to the K-, L- and M- series x-ray photons (with energies between 10 and 300 keV) emitted during the cascade of the muonic neon ion. The detectors were also used alone to record single photon events of the K- and L-series x rays. The observed intensity ratios of the K-series x rays provided a lower limit on the initial population of the 2S-state.;For the pressure condition of 40 Torr of neon, the 2S population was found to be 1.75% {dollar}\pm{dollar}.15% of the total cascade. The number of events at 40 Torr that could be attributed to two photon decays of the 2S-state was found to be 30 {dollar}\pm{dollar} 52 corresponding to a 2S population of 3.8% {dollar}\pm{dollar} 6.5%. at 400 Torr of neon the observed number of 2S two photon decays was 7 {dollar}\pm{dollar} 41, placing an upper limit on the 2S population at 0.9% {dollar}\pm{dollar} 5.1% of the total cascade. These results, to within the experimental uncertainties, can neither establish nor exclude the metastability of 2S muonic neon.

No description available.

In the last few decades, coherent light-atom interactions have opened unprecedented possibilities for the coherent control of atomic and optical quantum systems, paved the way for the practical realization of quantum information technologies, and allowed for the creation of novel quantum-enhanced sensors. This dissertation investigates the interaction of multiple near-resonant optical fields with hot rubidium atoms under the conditions of electromagnetically induced transparency. The main goal of the presented research is to address some fundamental challenges in using such systems for practical applications. The EIT effect relies on the strong coupling of an optical probe field and a collective long-lived ensemble of atomic spins by the means of a strong classical optical control field in a Lambda configuration. While optically-thick atomic vapor is necessary to achieve such a strong coupling regime, the increasing optical depth of the atomic ensemble also leads to the effective enhancement of other nonlinear light-atom interactions, such as the four-wave mixing effect. Here we discuss the possibility to control four-wave mixing in a three-level system without deteriorating the coherent properties of EIT by introducing an additional absorber resonant exclusively with the Stokes field. The exclusive detection of a weak probe field in the presence of a strong control field is a challenging experimental task, especially at the few-photon level. Many experiments employ polarization and/or frequency filtering to compete the task. We present an alternative filtering technique based on optical vortices for cases when the traditional methods are not sufficient or restrict the experimental arrangements. Finally, we demonstrate the possibility to manipulate the group velocity of a pulsed squeezed vacuum field by using the optical dispersion modification via Zeeman spin coherence in rubidium atoms. By changing the interaction condition, we demonstrate the switch between the ``slow'' and (for the first time) ``fast'' light regime. We also show that increased optical depth simultaneously leads to the enhancement of pulse advancement and the deterioration of squeezing fidelity in the output pulses.

In this work, we present state-of-the-art numerical methods and their applications for computing a particular class of observables using lattice quantum chromodynamics (Lattice QCD), a discretized version of the fundamental theory of quarks and gluons. These observables require calculating so called "disconnected diagrams" and are important for understanding many aspects of hadron structure, such as the strange content of the proton. We begin by introducing the reader to the key concepts of Lattice QCD and rigorously define the meaning of disconnected diagrams through an example of the Wick contractions of the nucleon. Subsequently, the calculation of observables requiring disconnected diagrams is posed as the computationally challenging problem of finding the trace of the inverse of an incredibly large, sparse matrix. This is followed by a brief primer of numerical sparse matrix techniques that overviews broadly used methods in Lattice QCD and builds the background for the novel algorithm presented in this work. We then introduce singular value deflation as a method to improve convergence of trace estimation and analyze its effects on matrices from a variety of fields, including chemical transport modeling, magnetohydrodynamics, and QCD. Finally, we apply this method to compute observables such as the strange axial charge of the proton and strange sigma terms in light nuclei. The work in this thesis is innovative for four reasons. First, we analyze the effects of deflation with a model that makes qualitative predictions about its effectiveness, taking only the singular value spectrum as input, and compare deflated variance with different types of trace estimator noise. Second, the synergy between probing methods and deflation is investigated both experimentally and theoretically. Third, we use the synergistic combination of deflation and a graph coloring algorithm known as hierarchical probing to conduct a lattice calculation of light disconnected matrix elements of the nucleon at two different values of the lattice spacing. Finally, we employ these algorithms to do a high-precision study of strange sigma terms in light nuclei; to our knowledge this is the first calculation of its kind from Lattice QCD.

This thesis presents progress in developing a trapped atom interferometer on a chip, based on AC Zeeman potentials. An atom interferometer is a high-precision measuring tool that can detect various types of forces and potentials. The trapped atom interferometer introduced in this thesis targets the shortcomings of traditional ballistic atom interferometers, which are typically meter-scale in height. Notably, a trapped atom interferometer has a localized atomic sample, a potentially longer interferometric phase accumulation time, and the prospect of being the basis for a more compact instrument. This thesis presents multiple projects in the development of a trapped atom interferometer based on the AC Zeeman potentials and traps: 1) production of ultracold potassium on a chip, 2) the theory of potential roughness in chip traps, 3) microwave chip trap design, and 4) a trapped atom interferometer with rubidium atoms, based on a laser dipole trap and an AC Zeeman force. (1) Potassium is a good candidate for the atom interferometer due to its bosonic and fermionic isotopes, multiple "magic" magnetic fields, and the convenience of RF and microwave trapping. The laser cooling and trapping system were upgraded to improve the temperature and population of potassium atoms in the chip trap. On-chip cooling resulted in a significant inelastic loss, which prevented the production of a potassium Bose-Einstein condensate. (2) Numerical simulations of chip wire defects predict that the AC Zeeman trapping potential should be substantially smoother than its DC Zeeman counterpart: the suppression of the roughness is due to magnetic polarization selection rules and the AC skin effect. (3) Furthermore, the thesis presents a number of studies on the straight and curved microstrip transmission lines that form the building blocks of the microwave atom chip for the AC Zeeman trap. (4) Finally, we constructed a rubidium-based Ramsey interferometer that can be converted to an atom interferometer by applying a spin-dependent AC Zeeman force: the interferometer was used to measure DC and AC Zeeman energy shifts and fringes were observed with an AC Zeeman force.

This thesis presents the first experimental demonstration of a two-wire AC Zeeman trap on an atom chip. The AC Zeeman energy is a resonant, bipolar, state-dependent atomic energy shift produced by alternating magnetic fields with frequencies near hyperfine transitions. We demonstrate that high gradients in this energy, as near an atom chip, can produce a spin-state selective force greater than gravity for ultracold rubidium atoms. Our novel trap is generated by a local minimum in AC Zeeman energy. Using less than one watt of power, we demonstrate trap frequency on the order of a few hundred Hz, trap depth about 5 μK, and quarter-second lifetimes. Motivated by trapped atom interferometry, this proof of principle AC Zeeman trap can also augment atom and ion experiments as a dynamic spin-dependent potential. Different parameters in the current arrangement can produce regions of linear gradient, flat saddle points, square- and donut-shaped traps, offering a new set of tools for atom chip experiments. This thesis also presents the relevant dressed atomic theory, four AC Zeeman trap designs, Rabi frequency measurements, numerical trap simulations, and the AC skin effect in wide rectangular wires.

Knowledge of the electric and magnetic elastic form factors of the nucleon is essential for an understanding of nucleon structure. of the form factors, the electric form factor of the neutron has been measured over the smallest range in Q2 and with the lowest precision. Jefferson Lab experiment 02-013 used a novel new polarized 3He target to nearly double the range of momentum transfer in which the neutron form factor has been studied and to measure it with much higher precision. Polarized electrons were scattered off this target, and both the scattered electron and neutron were detected. GEn was measured to be 0.0242 +/- 0.0020(stat) +/- 0.0061(sys) and 0.0247 +/- 0.0029(stat) +/- 0.0031(sys) at Q2 = 1.7 and 2.5 GeV2, respectively.

Solid state deuteron NMR experiments, especially magic angle spinning (MAS) and off-magic angle spinning (OMAS), are developed to explore dynamical systems. A theoretical discussion of interactions relevant for spin-1 nuclei is presented. Practical aspects of MAS/OMAS experiments are described an detail. The dominant quadrupolar coupling interaction in deuteron NMR has been simulated and the effects of multiple-frame molecular motions on MAS/OMAS spectra are taken into account in this calculation. Effects of chemical shift anisotropy are also simulated, and shown to be small under conditions of rapid sample spinning.;Two numerical methods, direct integration and an efficient simulation routine based on Floquet thoery, are discussed. Improvements in computational efficiency of the Floquet method in computing solid stae deuteron MAS/OMAS spectrum makes the quantitative analysis of molecular motion possible: complex multiple frame molecular motions, deuteron quadrupolar interactions and chemical shift anisotropy are now included in a single simulation routine and the effects of the multiple-frame molecular motions can be analyzed by comparing the line shapes of simulations with those of experiments.;The enhanced motional sensitivity of deuteron NMR MAS/OMAS makes it possible to detect temperature-dependent motion rates of urea molecules in octanoic acid/urea inclusion compounds. Temperature-dependent deuteron OMAS line shapes have been recorded and fitted through least-square procedures, to provide rates of rotation about both CN and CO bonds. Activation energies have been calculated for these motions. The power and utility of OMAS is demonstrated by this investigation.;The phenyl ring motions in appropriately labeled L-phenylalanine and N-acetyl-L-phenylalanine methyl ester/cyclodextrin inclusion compound have also been studied through high field deuteron MAS experiments. Phenylalanine MAS spectra with ultra-fast ring-flip motion have been simulated and the range of phenyl ring flip rates is obtained by comparing the simulated and experimental spectra. In the studies of phenylalanine/cyclodextrin inclusion compound, an approach to a physically reasonable diffusion model has also been made by increasing the number of jump sites per unit solid angle included in the calculation. These simulations involve repeated diagonalization of very large matrices and demonstrate the capability of the approach to handle complex dynamical systems.