Factors controlling the shape of the upper f region under daytime equilibrium conditions
Shape of upper f-region - equilibrium solutions for continuity equation for atomic oxygen ions in terms of exponential series
CONTINUITY EQUATION↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Ionospheric reaction rates in the light of recent measurements in the ionosphere and the laboratory, II
Consistency of laboratory measurements of ion-molecule reaction rates and recombination coefficients with mass spectrometric data on ionospheric ion density
ION-ATOM INTERACTION↗
Ejection and electronic excitation of foil particles by heavy-ion impact
Uranium ion impact ejection and electronic excitation of thin foil particles, observing optical spectra of Be, carbon and Al atoms and ions
Radziemski, L. J., Jr.↗
Introduction to the Contributions of A. Temkin and R. J. Drachman to Atomic Physics
Their work, as is the work of most atomic theorists, is concerned with solving the Schroedinger equation accurately for wave function in cases where there is no exact analytical solution. In particular, Temkin is associated with electron scattering from atoms and ions. When he started there already were a number of methods to study the scattering of electrons from atoms.
Bhatia, A.K.↗
Comparing the kinetics of ionized and neutral atoms from single and multi-element laser-produced plasmas
In this work, kinetics of ion and neutral atom emission features were compared for nanosecond laser-produced plasmas generated from several metal targets (i.e., Al, Ti, Zr, Nb, Ta) and an alloy containing all of these as principal alloying elements. Plasmas were produced by focusing 6 ns, 1064 nm pulses from an Nd:YAG laser on the targets of interest in a vacuum. A Faraday cup was used for collecting ion temporal features while spatially and temporally resolved emission spectroscopy was used for measuring the optical time of flight of various neutral atomic transitions. Our results highlight that most probable ion and atom velocities decay with increasing atomic mass. Trends for ions from the alloy target represent a weighted average where all ions contribute. For both ions and atoms, velocities decrease with increasing heat of vaporization and melting temperature, consistent with the thermal mechanisms that contribute to nanosecond laser ablation. Kinetic energies for neutral atoms from pure metal targets have some variability with atomic mass, whereas kinetic energies for atoms from the alloy target are more similar. These more similar kinetic energies observed for neutral atoms in the multi-element plasma may be attributed to collisions between species from all elements in the Knudsen layer.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Investigation of kilovolt ion sputtering Quarterly progress report, Aug. - Oct. 1966
Sputtering yields, angular and energy distribution of atoms, and implanted ion distribution in cesium and mercury surface interactions
MERCURY /METAL/↗
Reactions between NO/+/ and metal atoms using magnetically confined afterglows
A new method of studying thermal energy ion-neutral collision processes involving nongaseous neutral atoms is described. A long magnetic field produced by a solenoid in a vacuum chamber confines a thermal-energy plasma generated by photoionization of gas at very low pressure. As the plasma moves toward the end of the field, it is crossed by a metal atom beam. Ionic products of ion-atom reactions are trapped by the field and both the reactant and product ions move to the end of the magnetic field where they are detected by a quadrupole mass filter. The cross sections for charge transfer between NO(+) and Na, Mg, Ca, and Sr and that for rearrangement between NO(+) and Ca have been obtained. The charge-transfer reaction is found strongly dominant over the rearrangement reaction that forms metallic oxide ions.
Lo, H. H.↗
Measured thermal ion environment of STS-3
The Plasma Diagnostic Package (PDP) on the third Space Shuttle Flight (STS- 3) included a Bennett RF ion mass spectrometer which surveyed the positive ion composition in the vicinity of the vehicle. The ion measurements both within and exterior to the Shuttle cargo bay show the pervasive influence of the Shuttle's own gaseous emissions on its immediate plasma environment. Within the bay the ion spectrometer detected copius quantities of ions when the Shuttle was in daylight and when the gas pressure at the surface of the PDP was enhanced. In general few cases of ion detection occurred when the bay was facing toward the Shuttle wake. The plasma near the Shuttle consisted predominately of O+ (16AMU) ions and ions with atomic masses of 18, 30, 32 and 44 AMU corresponding to H2O+, NO+, O2+, and CO2+. All of these ions with the exception of H2O+ and CO2+ are expected ambient ions at the Shuttle's altitude of 240 km. During some thruster firings the 18 and 30 AMU ion concentrations detected within the bay increase by up to an order of magnitude within the 2.4 second sweep of the instrument. During these latter events the O+ distributions did not show a similar change.
Grebowsky, J. M.↗
Cross section for ionization of alkali atoms by collision with excited noble gas atoms.
MHD power generator in which ionization of alkali atoms occurs by collision with excited noble gas atoms, calculating velocity-dependent cross section
MAGNETOHYDRODYNAMIC GENERATOR↗
High-Energy Electron-Ion and Photon-Ion Collisions: Status and Challenges
Non-LTE plasmas are ubiquitous in objects studied in the UV and X-ray energy bands. Collisional and photoionization cross sections for atoms and ions are fundamental to our ability to model such plasmas. Modeling is key in the X-ray band, where detector properties and limited spectral resolution limit the ability to measure model-independent line strengths, or other spectral features. Much of the motivation for studying such collisions and many of the tools, are not new. However, the motivation for such studies and their applications, have been affected by the advent of X-ray spectroscopy with the gratings on Chandra and XMM-Newton. In this talk I will review this motivation and describe the tools currently in use for such studies. I will also describe some current unresolved problems and the likely future needs for such data.
Kallman, Timothy R.↗
Atomic order of rare earth ions in a complex oxide: a path to magnetotaxial anisotropy
Abstract Complex oxides offer rich magnetic and electronic behavior intimately tied to the composition and arrangement of cations within the structure. Rare earth iron garnet films exhibit an anisotropy along the growth direction which has long been theorized to originate from the ordering of different cations on the same crystallographic site. Here, we directly demonstrate the three-dimensional ordering of rare earth ions in pulsed laser deposited (Eu x Tm 1-x ) 3 Fe 5 O 12 garnet thin films using both atomically-resolved elemental mapping to visualize cation ordering and X-ray diffraction to detect the resulting order superlattice reflection. We quantify the resulting ordering-induced ‘magnetotaxial’ anisotropy as a function of Eu:Tm ratio using transport measurements, showing an overwhelmingly dominant contribution from magnetotaxial anisotropy that reaches 30 kJ m −3 for garnets with x = 0.5. Control of cation ordering on inequivalent sites provides a strategy to control matter on the atomic level and to engineer the magnetic properties of complex oxides.
Science & Technology - Other Topics↗
High-bandwidth CMOS-voltage-level electro-optic modulation of 780 nm light in thin-film lithium niobate
Integrated photonics operating at visible-near-infrared (VNIR) wavelengths offer scalable platforms for advancing optical systems for addressing atomic clocks, sensors, and quantum computers. The complexity of free-space control optics causes limited addressability of atoms and ions, and this remains an impediment on scalability and cost. Networks of Mach-Zehnder interferometers can overcome challenges in addressing atoms by providing high-bandwidth electro-optic control of multiple output beams. Here, we demonstrate a VNIR Mach-Zehnder interferometer on lithium niobate on sapphire with a CMOS voltage-level compatible full-swing voltage of 4.2 V and an electro-optic bandwidth of 2.7 GHz occupying only 0.35 mm 2 . Our waveguides exhibit 1.6 dB/cm propagation loss and our microring resonators have intrinsic quality factors of 4.4 × 10 5 . This specialized platform for VNIR integrated photonics can open new avenues for addressing large arrays of qubits with high precision and negligible cross-talk.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Anomaly of the composition of the F-2 equatorial region of the ionosphere during the hours after sunset according to data from the mass-spectrometer experiment on the Cosmos-274
A mass spectrometer on board Cosmos-274 measured concentrations of light atoms and ions. While traversing the geomagnetic equator during the evening hours it recorded on anomalous drop in ionized molecular oxygen and ionized atomic oxygen and nitrogen. A similar, less dramatic, decline was observed in the concentration of neutral atomic oxygen. A possible explanation for this and previously observed behavior is an ascent in altitude of the F layer in the hours after sunset, a possibility which is supported by calculations.
Gaydukov, V. Y.↗
Thermal diffusion in partially ionized gases - The case of unequal temperatures
Previous calculations of thermal diffusion coefficients in partially ionized gases are extended to the case of unequal neutral and ion temperatures and/or temperature gradients. Formulas are derived for the general case of a major gas as well as for minor atoms and ions. Strong enhancements of minor-ion thermal diffusion coefficients over their values in the fully ionized gas are found when the degree of ionization in the main gas is relatively low. However, compared to the case of equal temperatures, the enhancements are less strong when the neutrals are cooler than the ions. The specific case of the H-H(+) mixture, which is important in the study of solar and stellar atmospheres, is discussed as an application.
Geiss, J.↗
Atom probe tomography characterization of ion and neutron irradiated Alloy 800H
Alloy 800H is a high temperature and creep resistant alloy, and is considered as a candidate alloy for use in Generation IV nuclear reactor systems. To clarify the alloy's behavior under irradiation, samples were subjected to single ion irradiations up to 20 dpa at 440°C, a dual ion/He irradiation to 17 dpa at 460°C, and a neutron irradiation to 17 dpa at 385°C. The irradiated microstructures were characterized using atom probe tomography to complement previously published transmission electron microscopy studies. Additionally, after single ion irradiation, sparse fine Al and Ti clusters were observed after 1dpa, while high number densities of nanoscale Ni-Al-Ti clusters, Cr-Ti rich carbides, and Si-decorated dislocation loops developed after 10 and 20 dpa. The microstructure formed during single ion irradiation exhibited a strong depth dependence. No significant differences were observed between the single and dual ion irradiations. While Ni-Al-Ti clusters, Cr-Ti rich carbides, and Si-decorated dislocation loops were also observed after neutron irradiation, the neutron-irradiated microstructure differed from those found in the ion-irradiated samples.
36 MATERIALS SCIENCE↗
Laser cooling of antihydrogen atoms
The photon—the quantum excitation of the electromagnetic field—is massless but carries momentum. A photon can therefore exert a force on an object upon collision 1 . Slowing the translational motion of atoms and ions by application of such a force 2,3 , known as laser cooling, was first demonstrated 40 years ago 4,5 . It revolutionized atomic physics over the following decades 6–8 , and it is now a workhorse in many fields, including studies on quantum degenerate gases, quantum information, atomic clocks and tests of fundamental physics. However, this technique has not yet been applied to antimatter. Here we demonstrate laser cooling of antihydrogen 9 , the antimatter atom consisting of an antiproton and a positron. By exciting the 1S–2P transition in antihydrogen with pulsed, narrow-linewidth, Lyman-α laser radiation 10,11 , we Doppler-cool a sample of magnetically trapped antihydrogen. Although we apply laser cooling in only one dimension, the trap couples the longitudinal and transverse motions of the anti-atoms, leading to cooling in all three dimensions. We observe a reduction in the median transverse energy by more than an order of magnitude—with a substantial fraction of the anti-atoms attaining submicroelectronvolt transverse kinetic energies. We also report the observation of the laser-driven 1S–2S transition in samples of laser-cooled antihydrogen atoms. The observed spectral line is approximately four times narrower than that obtained without laser cooling. The demonstration of laser cooling and its immediate application has far-reaching implications for antimatter studies. A more localized, denser and colder sample of antihydrogen will drastically improve spectroscopic 11–13 and gravitational 14 studies of antihydrogen in ongoing experiments. Furthermore, the demonstrated ability to manipulate the motion of antimatter atoms by laser light will potentially provide ground-breaking opportunities for future experiments, such as anti-atomic fountains, anti-atom interferometry and the creation of antimatter molecules.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Rocket-borne measurements of particle fluxes and auroral light.
Rocketborne measurements of electron precipitation and relative brightness of ionized molecular nitrogen ion and atomic oxygen auroral emissions
NITROGEN ION↗
Low-Energy Electron Elastic Collisions with Actinide Atoms Am, Cm, Bk, Es, No and Lr: Negative-Ion Formation
The rigorous Regge-pole method is used to investigate negative-ion formation in actinide atoms through electron elastic total cross sections (TCSs) calculation. The TCSs are found to be characterized generally by negative-ion formations, shape resonances and Ramsauer-Townsend(R-T) minima, and they exhibit both atomic and fullerene molecular behavior near the threshold. Additionally, a polarization-induced metastable cross section with a deep R-T minimum is identified near the threshold in the Am, Cm and Bk TCSs, which flips over to a shape resonance appearing very close to the threshold in the TCSs for Es, No and Lr. We attribute these new manifestations to size effects and orbital collapse significantly impacting the polarization interaction. From the TCSs unambiguous and reliable ground, metastable and excited states negative-ion binding energies (BEs) for Am−, Cm−, Bk−, Es−, No− and Lr− anions formed during the collisions are extracted and compared with existing electron affinities (EAs) of the atoms. The novelty of the Regge-pole approach is in the extraction of the negative-ion BEs from the TCSs. We conclude that the existing theoretical EAs of the actinide atoms and the recently measured EA of Th correspond to excited anionic BEs.
Msezane, Alfred Z. (ORCID:0000000212485661)↗