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At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Helium and Neon in Comets

Two comets were observed with EUVE in late 1994. Both comet Mueller and comet Borrelly are short-period comets having well established orbital elements and accurate ephemerides. Spectra of 40 ksec were taken of each. No evidence for emission lines from either Helium or Neon was detected. We calculated limits on the production rates of these atoms (relative to solar) assuming a standard isotropic outflow model, with a gas streaming speed of 1 km/s. The 3-sigma (99.7% confidence) limits (1/100,000 for He, 0.8 for Ne) are based on a conservative estimate of the noise in the EUVE spectra. They are also weakly dependent on the precise pointing and tracking of the EUVE field of view relative to the comet during the integrations. These limits are consistent with ice formation temperatures T greater than or equal to 30 K, as judged from the gas trapping experiments of Bar-Nun. For comparison, the solar abundances of these elements are He/O = 110, Ne/O = 1/16. Neither limit was as constraining as we had initially hoped, mainly because comets Mueller and Borrelly were intrinsically less active than anticipated.

Jewitt, David↗
NASA NTRS1999

Laser Optogalvanic Spectroscopy pf Neon and Argon in a Discharge Plasma and its Significance for Microgravity Combustion

A detailed study of combustion mechanisms in flames, employing laser-based diagnostics, has provided good knowledge and understanding of the physical phenomena, and led to better characterization of the dynamical and chemical combustion processes, both under low-gravity (in space) and normal gravity (in ground based facilities, e.g. drop towers). Laser induced fluorescence (LIF), laser-induced incandescence (LII) and LIF thermometry have been widely used to perform nonintrusive measurements and to better understand combustion phenomena. Laser optogalvanic (LOG) spectroscopy has well-established applications in ion mobility measurements, atomic and molecular spectroscopy, ionization rates, recombination rates, velocity measurements and as a combustion probe for trace element detection. Absorption spectra of atomic and molecular species in flames can be obtained via LOG spectroscopy by measuring the voltage and current changes induced by laser irradiation. There are different kinds of processes that contribute to a discharge current, namely: (1) electron impact ionization, (2) collisions among the excited atoms of the discharge species and (3) Penning ionization. In general, at higher discharge currents, the mechanism of electron impact ionization dominates over Penning ionization, whereby the latter is hardly noticeable. In a plasma, whenever the wavelength of a laser coincides with the absorption of an atomic or molecular species, the rate of ionization of the species momentarily increases or decreases due to laser-assisted acceleration of collisional ionization. Such a rate of change in the ionization is monitored as a variation in the transient current by inserting a high voltage electrode into the plasma. Optogalvanic spectroscopy in discharges has been useful for characterizing laser line-widths and for providing convenient calibration lines for tunable dye lasers in the ultraviolet, visible and infrared wavelength regions. Different kinds of quantitative information, such as the electron collisional ionization rate, can be extracted from the complex processes occurring within the discharge. In the optogalvanic effect (OGE), there is no problem of overlap from background emissions, and hence even weak signals can be detected with a high signal-to-noise ratio, which makes the optogalvanic effect sensitive enough to resolve vibrational changes in molecular bonds and differences in energy levels brought about by different electron spins. For calibration purposes, neon and argon gaseous discharges have been employed most extensively, because these gases are commonly used as buffer gases within hollow-cathode lamps and provide an acceptable density of calibration lines. In the present work, our main aim has been to understand the dominant physical processes responsible for the production of the OGE signal, based on the extensive time resolved optogalvanic waveforms recorded, and also to extract quantitative information on the rates of excited state collisional processes.

Misra, Prabhakar↗
NASA NTRS2018

The Lunar Neon Exosphere Seen in LACE Data

Using the LACE data from Apollo 17 we have found measured neon densities consistent with the 20Ne surface number densities reported by Cook et al. (2013) for normal conditions, terminator surface densities of 3 (±1.5) × 10(exp 3) per cu.cm. These values are almost an order of magnitude less than those reported by Benna et al. (2015) for CME conditions. Using a Monte Carlo model and assuming the normal solar wind and a photoionization lifetime for Ne of 300 days, our result was more consistent with the Benna (2015) result than our measured result. Two lunations showed an increase in Ne during the night, consistent with the simulation, but two of the lunations showed a decrease in surface number density through the night. We have shown that explaining the Ne distribution is not as simple as assuming dynamic equilibrium with the solar wind and an exosphere accommodated to the local surface temperature.

LACE Data↗
DOE OSTI2023

Multi-MeV Electrons from Above-Threshold Ionization of the Neon K-Shell

We present measurements of integrated electron energies produced by above-threshold ionization (ATI) of neon in a laser field with intensity exceeding 10 20 W/cm 2 . We observe electrons with energy exceeding 10 MeV ejected in the laser forward direction above a threshold intensity of 2 ×10 20 W/cm 2 . Here, we compare to ATI models using both tunneling (ADK-PPT) and barrier suppression ionization and observe the onset of ATI at a higher threshold intensity than predicted by these 15 models.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2015

Observation of narrow isotopic optical magnetic resonances in individual emission spectral lines of neon

Narrow resonances are observed in the course of recording the individual emission lines of the glow discharge in the mixture of isotopes {sup 20}Ne and {sup 22}Ne, depending on the strength of the longitudinal magnetic field. The position of resonances in the magnetic scale corresponds to the compensation of the isotopic shift for certain spectral lines due to the Zeeman effect. It is found that the contrast of the resonances is higher for the transitions between the highly excited energy levels, and the resonances themselves are formed in the zone of longitudinal spatial nonuniformity of the magnetic field. (laser applications and other topics in quantum electronics)

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2013

Studying some mechanical properties of MgO with used neon bulb glass

Ceramic compact of MgO +WT% of UNBG were sintered at different sintering temperature (700, 900, 1100, 1300)°c, under static air for 3 hours. X-ray diffraction and some mechanical properties were conducted. The maximum sintered density, compression; fracture strength and hardness were indicated for the compilation of MgO −20 WT % UNBG, sintered at 1300 °c.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Filamentary structure of plasma produced by compression of puffing deuterium by deuterium or neon plasma sheath on plasma-focus discharge

The present experiments were performed on the PF-1000 plasma focus device at a current of 2 MA with the deuterium injected from the gas-puff placed in the axis of the anode face. The XUV frames showed, in contrast with the interferograms, the fine structure: filaments and spots up to 1 mm diameter. In the deuterium filling, the short filaments are registered mainly in the region of the internal plasmoidal structures and their number correlates with the intensity of neutron production. The longer filamentary structure was recorded close to the anode after the constriction decay. The long curve-like filaments with spots were registered in the big bubble formed after the pinch phase in the head of the umbrella shape of the plasma sheath. Filaments can indicate the filamentary structure of the current in the pinch. Together with the filaments, small compact balls a few mm in diameter were registered by both interferometry and XUV frame pictures. They emerge out of the dense column and their life-time can be greater than hundreds of ns.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Photoionized plasmas induced in neon with extreme ultraviolet and soft X-ray pulses produced using low and high energy laser systems

A comparative study of photoionized plasmas created by two soft X-ray and extreme ultraviolet (SXR/EUV) laser plasma sources with different parameters is presented. The two sources are based on double-stream Xe/He gas-puff targets irradiated with high (500 J/0.3 ns) and low energy (10 J/1 ns) laser pulses. In both cases, the SXR/EUV beam irradiated the gas stream, injected into a vacuum chamber synchronously with the radiation pulse. Irradiation of gases resulted in formation of photoionized plasmas emitting radiation in the SXR/EUV range. The measured Ne plasma radiation spectra are dominated by emission lines corresponding to radiative transitions in singly charged ions. A significant difference concerns origin of the lines: K-shell or L-shell emissions occur in case of the high and low energy irradiating system, respectively. In high energy system, the electron density measurements were also performed by laser interferometry, employing a femtosecond laser system. A maximum electron density for Ne plasma reached the value of 2·10{sup 18 }cm{sup −3}. For the low energy system, a detection limit was too high for the interferometric measurements, thus only an upper estimation for electron density could be made.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

The stereo-dynamics of collisional autoionization of ammonia by helium and neon metastable excited atoms through molecular beam experiments

A combined analysis of both new (energy spectra of emitted electrons) and previously published (ionization cross sections) experimental data, measured under the same conditions and concerning electronically excited lighter noble gas –NH{sub 3} collisional autoionization processes, is carried out. Such an analysis, performed by exploiting a formulation of the full potential energy surface both in the real and imaginary parts, provides direct information on energetics, structure, and lifetime of the intermediate collision complex over all the configuration space. The marked anisotropy in the attraction of the real part, driving the approach of reagents, and the selective role of the imaginary component, associated to the charge transfer coupling between entrance and exit channels, suggests that reactive events occur almost exclusively in the molecular hemisphere containing the nitrogen lone pair. Crucial details on the stereo-dynamics of elementary collisional autoionization processes are then obtained, in which the open shell nature of the disclosed ionic core of metastable atom plays a crucial role. The same analysis also suggests that the strength of the attraction and the anisotropy of the interaction increases regularly along the series Ne{sup *}({sup 3}P), He{sup *}({sup 3}S), He{sup *}({sup 1}S)–NH{sub 3}. These findings can be ascribed to the strong rise of the metastable atom electronic polarizability (deformability) along the series. The obtained results can stimulate state of the art ab initio calculations focused on specific features of the transition state (energetics, structure, lifetime, etc.) which can be crucial for a further improvement of the adopted treatment and to better understand the nature of the leading interaction components which are the same responsible for the formation of the intermolecular halogen and hydrogen bond.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

WAVELENGTH MEASUREMENTS OF K TRANSITIONS OF OXYGEN, NEON, AND MAGNESIUM WITH X-RAY ABSORPTION LINES

Accurate atomic transition data are important in many astronomical research areas, especially for studies of line spectroscopy. Whereas transition data of He-like and H-like ions (i.e., ions in high-charge states) have been accurately calculated, the corresponding data of K transitions of neutral or low-ionized metal elements are still very uncertain. Spectroscopy of absorption lines produced in the interstellar medium (ISM) has been proven to be an effective way to measure the central wavelengths of these atomic transitions. In this work, we analyze 36 Chandra High Energy Transmission Grating observations to search for and measure the ISM absorption lines along sight lines to 11 low-mass X-ray binaries. We correct the Galactic rotation velocity to the rest frame for every observation and then use two different methods to merge all the corrected spectra to a co-added spectrum. However, the co-added spectra obtained by this method exhibit biases, toward to either observations with high counts or lines with high signal-to-noise ratios. We do a Bayesian analysis of several significantly detected lines to obtain the systematic uncertainty and the bias correction for other lines. Compared to previous studies, our results improve the wavelength accuracy by a factor of two to five and significantly reduce the systematic uncertainties and biases. Several weak transitions (e.g., 1s-2p of Mg IV and Mg V; 1s-3p of Mg III and Mg V) are also detected for the first time, albeit with low significance; future observations with improved accuracy are required to confirm these detections.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

HUBBLE SPACE TELESCOPE EMISSION-LINE GALAXIES AT z ∼ 2: THE MYSTERY OF NEON

We use near-infrared grism spectroscopy from the Hubble Space Telescope to examine the strength of [Ne III] λ3869 relative to Hβ, [O II] λ3727, and [O III] λ5007 in 236 low-mass (7.5 ≲ log (M {sub *}/M {sub ☉}) ≲ 10.5) star-forming galaxies in the redshift range 1.90 < z < 2.35. By stacking the data by stellar mass, we show that the [Ne III]/[O II] ratios of the z ∼ 2 universe are marginally higher than those seen in a comparable set of local Sloan Digital Sky Survey galaxies, and that [Ne III]/[O III] is enhanced by ∼0.2 dex. We consider the possible explanations for this ∼4σ result, including higher oxygen depletion out of the gas phase, denser H II regions, higher production of {sup 22}Ne via Wolf-Rayet stars, and the existence of a larger population of X-ray obscured active galactic nuclei at z ∼ 2 compared to z ∼ 0. None of these simple scenarios, alone, are favored to explain the observed line ratios. We conclude by suggesting several avenues of future observations to further explore the mystery of enhanced [Ne III] emission.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

Quantum beat oscillations in the two-color-photoionization continuum of neon and their dependence on the intensity of the ionizing laser pulse

We investigate quantum beat oscillations in the photoionization continuum of Ne atoms that are photoionized by absorption of two photons via a group of excited bound states using ultrashort extreme ultraviolet and infrared laser pulses. The extreme ultraviolet pulse starts an excited-state wave packet that is photoionized by a high-intensity infrared pulse after a variable time delay. We analyze the continuum quantum beats from this two-step photoionization process and their dependence on the photoelectron kinetic energy. We find a pronounced dependence of the quantum beat amplitudes on the photoelectron kinetic energy. The dependence changes significantly with the applied infrared laser-pulse intensity. The experimental results are in good qualitative agreement with a model calculation that is adapted to the experimental situation. It accounts for the intensity dependence of the quantum beat structure through the coupling of the excited-state wave packet to other bound Ne states induced by the high-intensity infrared laser pulse.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2016

Neon and [C II] 158 μm emission line profiles in dusty starbursts and active galactic nuclei

A sample of 379 extragalactic sources is presented that has mid-infrared, high-resolution spectroscopy from the Spitzer Infrared Spectrograph (IRS) and also spectroscopy of the [C ii] 158 μm line from the Herschel Photodetector Array Camera and Spectrometer (PACS). The emission line profiles of [Ne ii] 12.81 μm, [Ne iii] 15.55 μm, and [C ii] 158 μm are presented, and intrinsic line widths are determined (full width half maximum of Gaussian profiles after instrumental correction). All line profiles, together with overlays comparing the positions of PACS and IRS observations, are made available in the Cornell Atlas of Spitzer IRS Sources. Sources are classified from active galactic nucleus (AGN) to starburst based on equivalent widths of the 6.2 μm polycyclic aromatic hydrocarbon feature. It is found that intrinsic line widths do not change among classifications for [C ii], with median widths of 207 km s{sup −1} for AGNs, 248 km s{sup −1} for composites, and 233 km s{sup −1} for starbursts. The [Ne ii] line widths also do not change with classification, but [Ne iii] lines are progressively broader from starburst to AGN. A few objects with unusually broad lines or unusual redshift differences in any feature are identified.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Neon-like Iron Ion Lines Measured in NIFS/Large Helical Device (LHD) and Hinode /EUV Imaging Spectrometer (EIS)

Line intensities emerging from the Ne-sequence iron ion (Fe xvii) are measured in the laboratory, by the Large Helical Device at the National Institute for Fusion Science, and in the solar corona by the EUV Imaging Spectrometer (EIS) on board the Hinode mission. The intensity ratios of Fe xvii λ 204.6/ λ 254.8 are derived in the laboratory by unblending the contributions of the Fe xiii and xii line intensities. They are consistent with theoretical predictions and solar observations, the latter of which endorses the in-flight radiometric calibrations of the EIS instrument. The still remaining temperature-dependent behavior of the line ratio suggests the contamination of lower-temperature iron lines that are blended with the λ 204.6 line.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1993

Dependence of the multiplicities of secondary particles on the impact parameter in collisions of high-energy neon and iron nuclei with photoemulsion nuclei

A method is proposed for finding the dependence of mean multiplicities of secondaries on the nucleus-collision impact parameter from the data on the total interaction ensemble. The impact parameter has been shown to completely define the mean characteristics of an individual interaction event. A difference has been found between experimental results and the data calculated in terms of the cascade-evaporation model at impact-parameter values below 3 fm.

Non-NASA Center↗