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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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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Determination of Multimode Motional Quantum States in a Trapped Ion System

Trapped atomic ions are a versatile platform for studying interactions between spins and bosons by coupling the internal states of the ions to their motion. Measurement of complex motional states with multiple modes is challenging, because all motional state populations can only be measured indirectly through the spin state of ions. Here we present a general method to determine the Fock state distributions and to reconstruct the density matrix of an arbitrary multimode motional state. Further, we experimentally verify the method using different entangled states of multiple radial modes in a five-ion chain. This method can be extended to any system with Jaynes-Cummings-type interactions.

74 ATOMIC AND MOLECULAR PHYSICS↗
NASA NTRS1992

Metallic atoms and ions in comets: Comet Halley 1986 3

The origin of metallic atoms and ions in the cometary comae is investigated theoretically. Two effects are revealed in the comas of bright comets: (1) the Na anomalous type effect is possible within the gas-dust jets of comet P/Halley 1986 3 due to cooling cometary dust by cryogenic gas flow from the nucleus; and (2) the production of ions of refractory elements (Fe(+), Si(+), etc.) at large heliocentric distances is possible in the comas of the Halley type dusty comets due to high-velocity impacts between cometary and zodiacal dust particles. Spectral observations of comets with high sensitivity and spatial resolution are important for studying both comets and interplanetary dust.

Ibadov, S.↗
DOE OSTI2020

Formula for the ionisation rate of an atom or ion in a strong electromagnetic field for numerical simulation

A formula is proposed for calculating the rate of field ionisation of an atom or ion, taking into account both tunnel ionisation and barrier suppression ionisation. Compared with the previous formula proposed in 2018, it more accurately describes the transition region between both ionisations and is determined mainly by two parameters: the ionisation potential of an atom or ion and the amplitude of an external electric field. This makes the presented formula suitable for use in numerical packages simulating the interaction of high-power laser radiation with matter by the particle-in-cell (PIC) method. (paper)

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1993

Dissociative recombination in planetary ionospheres

Ionization in planetary atmospheres can be produced by solar photoionization, photoelectron impact ionization, and, in auroral regions, by impact of precipitating particles. This ionization is lost mainly in dissociative recombination (DR) of molecular ions. Although atomic ions cannot undergo DR, they can be transformed locally through ion-molecule reactions into molecular ions, or they may be transported vertically or horizontally to regions of the atmosphere where such transformations are possible. Because DR reactions tend to be very exothermic, they can be an important source of kinetically or internally excited fragments. In interplanetary thermospheres, the neutral densities decrease exponentially with altitude. Below the homopause (or turbopause), the atmosphere is assumed to be throughly mixed by convection and/or turbulence. Above the homopause, diffusion is the major transport mechanism, and each species is distributed according to its mass, with the logarithmic derivative of the density with repect to altitude given approximately by -1/H, where H = kT/mg is the scale height. In this expression, T is the neutral temperature, g is the local acceleratiion of gravity, and m is the mass of the species. Thus lighter species become relatively more abundant, and heavier species less abundant, as the altitude increases. This variation of the neutral composition can lead to changes in the ion composition; furthermore, as the neutral densities decrease, dissociative recombination becomes more important relative to ion-neutral reactions as a loss mechanism for molecular ions.

Fox, J. L.↗
NASA NTRS1960

Energies of Various Interactions Between Hydrogen and Helium Atoms and Ions

A compilation is made of those interactions between hydrogen and helium atoms and ions whose potential curves are well established by virtue of being based on experimental data or on essentially exact quantum-mechanical calculations. These potential curves have been fitted with well-known empirical forms which should be useful in calculations of transport properties involving these interactions.

Fallon, Robert J.↗
NASA NTRS1971

Surface field analysis of splitting of orbitals of atoms and ions approaching a metal surface.

The splitting of p- and d-orbitals of an atom or an ion which is caused by the locally varying potential near the surface of a realistic metal has been studied for bcc and fcc substrates. A quasi-ionic model is reasonable at close distance, inasmuch as the electron gas does not completely screen the ionic cores. The arrangement of ion cores near the surface causes the potential to vary in three dimensions. Expressions for energy levels were derived for an unsymmetric group using the quasi-ionic model and techniques used in the treatment of crystal field of nearest neighbors. A number of cases involving ions, as well as atoms in the vicinity of a metal substrate were numerically evaluated.

Rao, P. V. S.↗
NASA NTRS1988

Atomic forces between noble gas atoms, alkali ions, and halogen ions for surface interactions

The components of the physical forces between noble gas atoms, alkali ions, and halogen ions are analyzed and a data base developed from analysis of the two-body potential data, the alkali-halide molecular data, and the noble gas crystal and salt crystal data. A satisfactory global fit to this molecular and crystal data is then reproduced by the model to within several percent. Surface potentials are evaluated for noble gas atoms on noble gas surfaces and salt crystal surfaces with surface tension neglected. Within this context, the noble gas surface potentials on noble gas and salt crystals are considered to be accurate to within several percent.

Wilson, J. W.↗
NASA NTRS1972

Photoionization cross-sections for atoms and ions of aluminum, silicon, and argon.

Photoionization cross sections for all levels belonging to the configurations of atoms and ions of aluminum, silicon, and argon have been calculated using Hartree-Fock bound-electron wave functions and close-coupling approximation free-electron wave functions. The results are presented in the form of a computationally convenient interpolation formula and should find wide astrophysical application.

Chapman, R. D.↗
NASA NTRS1989

Charge exchange transition probability for collisions between unlike ions and atoms within the adiabatic approximation

A simple formula for the transition probability for electron exchange between unlike ions and atoms is established within the adiabatic approximation by employing the Linear Combination of Atomic Orbitals (LCAO) method. The formula also involves an adiabatic parameter, introduced by Massey, and thus the difficulties arising from the internal energy defect and the adiabatic approximation are avoided. Specific reactions Li(+++) + H to Li(++) + H(+) and Be(4+) + H to Be(3+) + H(+) are considered as examples. The calculated capture cross section results of the present work are compared with the experimental data and with the calculation of other authors over the velocity range of 10(7) cm/sec to 10(8) cm/sec.

Xu, Y. J.↗
NASA NTRS1979

Continuum Absorption Coefficient of Atoms and Ions

The rate of heat transfer to the heat shield of a Jupiter probe has been estimated to be one order of magnitude higher than any previously experienced in an outer space exploration program. More than one-third of this heat load is due to an emission of continuum radiation from atoms and ions. The existing computer code for calculating the continuum contribution to the total load utilizes a modified version of Biberman's approximate method. The continuum radiation absorption cross sections of a C - H - O - N ablation system were examined in detail. The present computer code was evaluated and updated by being compared with available exact and approximate calculations and correlations of experimental data. A detailed calculation procedure, which can be applied to other atomic species, is presented. The approximate correlations can be made to agree with the available exact and experimental data.

Armaly, B. F.↗
NASA NTRS2002

Interchannel Coupling in the Photoionization of Atoms and Ions in the X-Ray Range

To understand how this interchannel coupling, so important in neutral atoms, applies to positive ions, a research program has been initiated to deal with this question, i.e., a program to quantify the effects of interchannel coupling in ionic photoionization, thereby assessing existing photoionization data bases in the x-ray region. To accomplish this task, we have employed the Relativistic Random-Phase-Approximation (RRPA) methodology which includes significant aspects of electron-electron correlation, including interchannel coupling. The RRPA methodology has been found to produce excellent agreement with experiment for neutral Ne at photon energies in the 1 keV range.

Manson, Steven T.↗