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Results for “ATOMIC EXCITATION”

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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

The response of the ionosphere to the injection of chemically reactive vapors

As a gas released in the ionosphere expands, it is rapidly cooled. When the vapor becomes sufficiently tenuous, it is reheated by collisions with the ambient atmosphere and its flow is then governed by diffusive expansion. As the injected gas becomes well mixed with the plasma, a hole is created by chemical processes. In the case of diatomic hydrogen release, depression of the electron concentrations is governed by the charge exchange reaction between oxygen ions and hydrogen, producing positive hydroxyl ions. Hydroxyl ions rapidly react with the electron gas to produce excited oxygen and hydrogen atoms. Enhanced airglow emissions result from the transition of the excited atoms to lower energy states. The electron temperature in the depleted region rises sharply causing a thermal expansion of the plasma and a further reduction in the local plasma concentration.

Bernhardt, P. A.↗
NASA NTRS1982

Containerless high temperature property measurements by atomic fluorescence

Laser induced fluorescence techniques were developed for the containerless study of high temperature processes, material properties, levitation, and heating techniques for containerless earth-based experimentation. Experiments were performed in which fluorescence of atomic aluminum, mercury, or tungsten were studied. These experiments include measurements of: (1) Al atom evaporation from CW CO2 laser heated and aerodynamically levitated sapphire and alumina spheres, and self-supported sapphire filaments, (2) Al atom reaction with ambient oxygen in the wake of a levitated specimen, (3) Hg atom concentrations in the wake of levitated alumina and sapphire spheres, relative to the ambient Hg atom concentration, (4) Hg atom concentrations in supersonic levitation jets, and (5) metastable, electronically excited W atom concentrations produced by evaporation of an electrically heated tungsten filament.

Nordine, P. C.↗
NASA NTRS1981

A spectroscopic experimental and computer-assisted empirical model for the production and energetics of excited oxygen molecules formed by atom recombination on shuttle tile surfaces

A visible emission spectroscopic method was developed. The amounts of excited singlet and triplet oxygen molecules produced by recombination on the Space Shuttle Orbiter thermal protective tiles at elevated temperatures are determined. Rate constants and energetics of the extremely exothermic reaction are evaluated in terms of a chemical and mathematical model. Implications for potential contribution to Shuttle surface reentry heating fluxes are outlined.

Owan, D. A.↗
DOE OSTI2024

Entanglement Generation in Weakly Driven Arrays of Multilevel Atoms via Dipolar Interactions

We investigate the driven-dissipative dynamics of multilevel atomic arrays interacting via dipolar interactions at subwavelength spacings. Unlike two-level atoms in the weakly excited regime, multilevel atoms can become strongly entangled. Here, the entanglement manifests as the growth of spin waves in the ground-state manifold and survives after turning off the drive. We propose the 2.9 μ⁢m transition between 3 P 2 ↔ 3 D 3 in 88 Sr with 389 nm trapping light as a platform to test our predictions and explore many-body physics with light-matter interactions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1966

Physics of molecules

Molecular physics research on maser spectroscopy, electron excitation, molecular spectra of cesium, and related topics

ATOMIC EXCITATION↗
NASA NTRS1978

The reaction of N/2D/ with O2 as a source of O/1D/ atoms in aurorae

The source of O(1D) atoms in the auroral ionosphere is investigated using sounding rocket data. Previously, it has been shown that the conventional sources of O(1D) atoms in the aurora, dissociative recombination of O2(plus) and electron impact excitation of atomic oxygen, fail to explain the measured 6300 A volume emission rate profile. It is suggested that the atom-atom interchange reaction of N(2D) with O2 can be the major source of auroral 6300 A emission if O(1D) is created with high efficiency.

Rusch, D. W.↗
NASA NTRS1979

Semiclassical study of reactive scattering in a laser field - F + H2 + barred-h times omega times /1.06 microns/ system

Semiclassical calculations of collinear F+H2(nu = 0) reactive and inelastic scattering in an Nd-glass laser field of various intensities are described. The decoupling approximation developed for the Miller-George theory is used for nonadiabatic transitions between the electronic-field surfaces, and special attention is paid to the choice of a proper coordinate system for applying the decoupling approximation. An increase in the total reaction probability and population ratio of the nu = 3 over nu = 2 vibrational state of HF occurs suddenly as the field intensity increases beyond 10 TW/sq cm. It is found that in a laser field the H2 molecule can be vibrationally excited while the F atom is electronically excited.

Yuan, J.-M.↗
NASA NTRS1985

Upper limits to (O) in the lower thermosphere from airglow

A method for estimating the upper limit to oxygen atom density in the lower thermosphere is presented. The method is based on an analytical equation for the energy density of recombination process, and the radiation of O2 atoms at excited levels. As an example of the method, upper limits of oxygen atom density are estimated for the CIRA (O2) reference atmosphere of 1972. The estimates are given in a table.

Sharp, W. E.↗
NASA NTRS1996

Spectral Irradiance Measurements of Simulated Lightning in Planetary Atmospheres

Optical emissions from lightning provide information to estimate the altitude, latitude and longitude of lightning storms, the energy of the discharges, and the production of important trace species such as HCN and C2H2. Knowledge of the spectra of planetary lightning is needed to deduce the total energy dissipated by lightning (and thereby, the production of trace gases) and to help design experiments to detect and track lightning storms. Measurements of the spectral irradiance from approximately 380 to 820 nm are reported for laboratory simulations of lightning in the atmospheres of Venus, Jupiter, and Titan. In our laboratory, laser-induced plasmas (LIP) are used to simulate lightning discharges. This technique avoids contamination of the spectra by elect-ode material and maintains a safe environment while allowing the use of flammable gases, such as hydrogen and methane, found in outer planet atmospheres. The observations were made at I and 5 bars pressure for Venus and Jupiter and at 1 bar for the Titan mixture. At a pressure of one bar, our results show prominent lines from H(sub alpha), H(sub beta), H(sub gamma), and H(sub delta) lines of the Balmer Series of atomic hydrogen, a single line from Helium at 588 nm and strong continuum radiation. At pressures of 5 bars, the H(sub alpha) and H(sub beta) lines are wider, the H(sub gamma), and H(sub delta) lines merge into the continuum because of pressure broadening, and the helium line at 588 nm is no longer visible. The observed spectra of simulated lightning in the venusian atmosphere at 1 and 5 bars shows that the OI multiplet at 777.7 nm dominates the spectra, but weak features due to atomic carbon and singly excited and singly ionized oxygen atoms are also visible. Although lightning has not yet been observed on Titan, it conceivable that some form of lightning discharge could be occurring. Therefore experiments on a Titan atmosphere mixture were conducted. The most prominent features seen in the simulated spectra are the H(sub alpha) at 656 nm. from the dissociation of the methane and two strong features at 740 and 820 nm from singly excited nitrogen atoms. Most of the features between 400 and 656 nm are due to ionized nitrogen atoms. A broad, highly structured feature centered near 389 nm is molecular band radiation from CN molecules formed in the cooling plasma of atomic nitrogen, carbon, and hydrogen. It is observed in the lightning simulations of both the venusian and Titan atmospheres, For Venus, Jupiter, and Titan, narrow spectral features that are ideal for detecting lightning in the presence of sunlight are present in the spectra. These features could allow lightning to be detected and tracked by Earth-based instruments.

Borucki, W. J.↗
NASA NTRS1972

Far UV camera/spectrograph

In March 1610, Galileo Galilei reported the first use of a telescope to view mountains and maria on the Moon. On April 21, 1972, the Apollo 16 commander pointed a somewhat more complex optical instrument at the Earth from the Moon and obtained several remarkable photographs showing atmospheric rather than surface features. The optical part of the far UV camera (aperture, 7.5 cm) was not much larger than Galileo's telescope. Like his, this instrument was also pointed at other celestial objects that Galileo viewed, including the Milky Way and Jupiter, and the Large Magellanic Cloud (LMC), which is not visible from Italy. More important, the far UV camera/spectrograph recorded light in the invisible band of wavelengths between 50 and 160 nm, approximately one-third the wavelength that can penetrate the atmosphere of the Earth to ground-based telescopes. As described in more detail in this section, these UV observations from the Moon allow study of the entire atmosphere of the Earth and the geocorona. The photographs show hydrogen and other gases in the solar wind and interplanetary media, and they provide new data on stars, nebulae, and galaxies much farther away. When used as a spectrograph, the instrument distributes the light it receives according to wavelength, and the resulting spectrum shows bright lines or gaps known to be characteristic of various gases, such as hydrogen (H), helium (He), oxygen (O), nitrogen (N), and neon (Ne). If a gas cloud is hot, the atoms are excited and the spectrum shows bright emission lines; if it is cool, the atoms absorb light, leaving gaps or absorption lines. The far UV camera is blind to ordinary visible light; for that reason, the photographs show very few of the stars mapped by ground-based telescopes. Only the very-high-temperature (blue) stars of spectral classes O, B, and possibly A (temperatures from 50000 ° down to 10000°K) are expected to be recorded. Image blackness or density on the negatives also depends on the brightness of the star, which astronomers measure in an inverted logarithmic scale of magnitudes. A star of 6 magnitudes (mag.) can barely be seen with the unaided eye. An 11-mag. star is 100 times fainter, and a 12-mag. star is 2.5 times fainter yet. The faintest star recorded by the far UV camera is at least 11 mag., which is called the limiting magnitude.

George R. Carruthers↗
NASA NTRS1988

Multichannel processes of H2O in the 18 eV region

Measurements were made of: (1) the fluorescence cross sections of OH(A 2Sigma+) fragments; (2) the absolute cross sections producing H atoms in the n = 2, 3, and 4 states; (3) the cross section for producing excited O atoms which has an upper limit of 5 x 10 to the -21 sq cm; and (4) the fluorescence cross section for producing H2(a 3Sigma g +) fragments. It is shown that, in the 16-20 eV region, there are excellent correspondences in the peak positions and spacings among the photoabsorption, photoionization spectra, and fluorescence functions of OH(A) and H(n).

Wu, C. Y. Robert↗
NASA NTRS1993

Optical probing of cold trapped atoms

Transitions between excited states of laser-cooled and laser-trapped rubidium and cesium atoms are probed by use of fiber and diode lasers. High-resolution Doppler-free spectra are detected by observation of the absorption and fluorescence of light from the intermediate level of two-step cascade systems. The optical double-resonance spectra show Autler-Townes splitting in the weak probe limit and more complicated spectra for a strongly coupled three-level system.

Fox, R. W.↗