SEARCH · Engineering Papers

Results for “LINE WIDTHS”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 325 records · Page 18

All sources NASA NTRS DOE OSTI

NASA NTRS1976

Ozone spectroscopy with a CO2 waveguide laser

Ozone spectral measurements were conducted with a waveguide CO2 laser, which was continuously tunable over a + or - 450-MHz region, about several lines in the P-branch of the band near the 9.5-micron wavelength region. A passively stabilized low-pressure CO2 laser was also used to provide reference CO2 frequencies. The frequencies of several ozone lines were determined in the nu-3 band, which are near CO2 laser line frequencies in the 9.5-micron wavelength region. The absolute measurement accuracy is estimated to be + or - 6 MHz, and the measurements indicate that the ozone line frequencies listed in currently available spectral compilations are 0.003-0.006 per cm too high. The size of this error is small by conventional IR standards, but extremely important when CO2 laser instruments are used to monitor stratospheric ozone, where line widths in this spectral region are typically 0.001/cm. Empirically determined absorption curves must be constructed in order to calibrate laser differential absorption instrument properly when low-altitude ozone measurements are conducted.

Menzies, R. T.↗

NASA NTRS1977

The Lyman alpha coronagraph

The rocket-borne Lyman alpha coronagraph (RLAC) is to be used in the absence of a natural solar eclipse to determine coronal temperatures from measurements of the line width of Lyman-alpha and to determine neutral hydrogen densities of coronal material from the absolute intensity. The coronagraph consists of a 75-cm Fastie-Ebert scanning spectrometer with an AMR 641 photoelectric detection system, an off-axis parabolic primary mirror, and an occulting system. A special optical arrangement achieves rejection of radiation from the solar disk.

Kohl, J. L.↗

NASA NTRS1977

Evolution of the high-temperature plasma in the 15 June 1973 flare

The evolution of the high-temperature plasma in the solar flare of June 15, 1973, is analyzed using XUV spectroheliograms obtained from Skylab. Preflare enhancement of loops in the active region is discussed, and the temperature and density of the hot plasma are determined as a function of time. The turbulent velocity in the high-temperature plasma is deduced from a comparison of line widths of the Fe XXIV doublet at 192 and 255 A. The results indicate that: (1) the flare occurred in a low-lying loop or loops; (2) the large-scale magnetic-field configuration of the active region did not change significantly; (3) the hot plasma observed in Fe XXIII-XXIV showed considerable dynamic activity, including an initial upward motion of the whole plasma with a velocity of about 80 km/s; (4) large turbulent mass motions took place in the Fe XXIII-XXIV plasma with random velocities of 100 to 160 km/s; (5) the temperature of the hot plasma was 14 million K at peak X-ray intensity, decreased slightly, and then remained at 12.6 million K before dropping to below 10 million K; and (6) there was a temperature gradient along the length of the loop, with the 14 million-K plasma near the top and progressively lower-temperature plasmas on either side.

Cheng, C.-C.↗

NASA NTRS1978

IUE observations of cool stars - Alpha Aurigae, HR1099, Lambda Andromedae, and Epsilon Eridani

Initial IUE observations of four cool stars are reported. Observed fluxes and surface fluxes are given for several UV emission lines in the spectral range 1175-2000 A, obtained at low and high dispersion with the short-wavelength spectrograph and camera. These lines are formed in the outer atmospheres of these stars, in regions presumably analogous to the solar chromosphere and transition region. The surface fluxes in the lines increase along the sequence: quiet sun, Epsilon Eri, Lambda And, Alpha Aur, and HR1099. The 2.8-d RS CVn-type binary HR1099, observed on 1 March 1978 near the end of a major flaring episode, has line surface fluxes roughly 100 times that of the quiet sun, similar to those seen in solar flares. Line profiles and flux ratios in multiplets for Capella are presented, and comments given on the opacity of the lines and on a tendency of line width to increase with temperature of formation.

Linsky, J. L.↗

NASA NTRS1980

improving maser frequency stability

Hydrogen maser frequency standard is more stable by addition of parallel pyrex capillary tube array collimator. With collimator, maser line width has been made as narrow as 0.24 hertz representing fivefold improvement over maser without collimator. Fluorocarbon coating in tubes virtually eliminates energy loss in collimator.

Crampton, S. B.↗

NASA NTRS1979

Molecules of significance in planetary aeronomy

This monograph is basically devoted to spectroscopic information of the molecules of planetary interest. Only those molecules have been dealt with which have been confirmed spectroscopically to be present in the atmosphere of major planets of our solar system and play an important role in the aeronomy of the respective planets. An introduction giving the general conditions of planets and their atmospheres including the gaseous molecules is given. Some typical planetary spectra is presented and supported with a discussion on some basic concepts of optical absorption and molecular parameters that are important to the study of planetary atmospheres. Quantities like dipole moments, transition probabilities, Einstein coefficients and line strengths, radiative life times, absorption cross sections, oscillator strengths, line widths and profiles, equivalent widths, growth curves, bond strengths, electronic transition moments, Franck-Condon factors and r-centroids, etc., are discussed. Spectroscopic information and relevant data of 6 diatomic (HF, HCL, CO, H2, O2, N2) and 6 polyatomic (CO2, N2), O3, HeO, NH3, CH4) molecules are presented.

Mohan, H.↗

NASA NTRS1978

Voltage tunable differential heterodyne spectroscopy in the far-infrared with Josephson junctions

The basic methods of differential heterodyne spectroscopy with Josephson junctions are described. A technique is outlined for bridging the gap between a local oscillator frequency and a signal frequency through the use of a voltage-tunable internal oscillation frequency in a Josephson junction structure. It is shown that an intermediate frequency can be converted to a conveniently low frequency by double frequency conversion carried out directly in a Josephson junction. The expected conversion efficiency is estimated qualitatively. Experiments are discussed in which the differential heterodyne frequency-conversion technique was demonstrated at a wavelength of 0.4 mm and a voltage-tunable oscillation in a double Josephson junction structure was observed, with oscillation line widths as narrow as 0.5 Hz, for a resistance of 3.3 nanohms and an estimated inductance of the order of 1 nH.

Ulrich, B. T.↗

NASA NTRS1979

Jovian sodium emission from Region C2

Observations of emission from sodium presumed to have been ejected from Io in the orbital plane of the Gallilean satellites and extending outward to at least 35 Jupiter radii are reported. Spectra of the sodium D line were observed to have an intensity of 20 to 30 R. Mechanisms for the escape of sodium from Io after sputtering from the surface are: (1) ejection from Io at velocities greater than Jupiter escape velocity, (2) ejection at velocities corresponding to orbits with apoapses of 35 Jupiter radii, and (3) ionization followed by magnetic field sweeping and recombination. The relative contributions of each mechanism are estimated and used to predict the sodium emission intensity at 35 Jupiter radii to be 7 to 8 R, a value considered to be in reasonable agreement with observations. Observations of emission line width and the correlation of intensity with the orbital phase of Io would provide further means of evaluating the proposed mechanisms of sodium ejection.

Pilcher, C. B.↗

NASA NTRS1979

Gyroharmonic emissions induced by energetic ions in the equatorial plasmasphere

A theoretical investigation shows that MeV ions observed in the plasmasphere which have a power law distribution function possessing strong pitch angle anisotropy can give rise to emissions at frequencies near the harmonics of the ion gyrofrequencies observed in the same region. These emissions are sustained by the low-beta sub c plasma in the plasmasphere. It is found that only emissions with frequencies along the fast magnetosonic branch may occur and that these waves are essentially perpendicularly propagating. Growth is restricted to frequencies immediately below the ion gyroharmonics by the resonance condition and implies line widths of about 0.001 Omega sub alpha. Observations of ion gyroharmonic emissions with spacings of 1/16, 1/8, and 3/16 of the proton gyrofrequency may indicate the existence of energetic ion O(+), O(2+), and O(3+), respectively.

Curtis, S. A.↗

NASA NTRS1979

An atomic model for neutral and singly ionized uranium

A model for the atomic levels above ground state in neutral, U(0), and singly ionized, U(+), uranium is described based on identified atomic transitions. Some 168 states in U(0) and 95 in U(+) are found. A total of 1581 atomic transitions are used to complete this process. Also discussed are the atomic inverse lifetimes and line widths for the radiative transitions as well as the electron collisional cross sections.

Maceda, E. L.↗

NASA NTRS1979

The 4-8 micron spectrum of the infrared source W33 A

The spectrum of the highly obscured infrared source W33 A from 4.5 to 8 microns is measured in order to investigate the intervening cold, dense interstellar material. Spectrophotometry at a relative spectral resolution of about 0.015 by an airborne filter-wheel infrared spectrometer reveals strong absorption features at 4.61, 5.99 and 6.78 microns. The absorption at 4.61 microns is attributed primarily to the fundamental vibration-rotation band of CO at a column density (at least 10 to the 19th/sq cm) which is 10% of the carbon inferred from silicate abundances. The strengths and line widths of the absorption agt 5.99 and 6.78 microns are interpreted as evidence of absorption in the resonance bands of carbonyl, carbon-carbon double, methyl and methylene bonds of hydrocarbons associated with interstellar dust.

Soifer, B. T.↗

NASA NTRS1979

Effect of ionophores on the rate of intramolecular cation exchange in durosemiquinone ion pairs

The effects of the ionophores 15-crown-5 (15C5), 18-crown-6 (18C6), dibenzo-18-crown-6 (DBC) and cryptand 222 (C222) on intramolecular cation exchange in ion pairs of the sodium salt of the durosemiquinone anion in benzene solution are investigated. Electron paramagnetic resonance spectra of the 18C6 and 15C5 complexes with durosemiquinone reduced by contact with a sodium mirror show an alternating line width which indicates that the sodium ion is being exchanged between equivalent sites near the oxygens of the semiquinone with activation energies of 8.7 and 6.0 kcal/mole and Arrhenius preexponential factors of 9 x 10 to the 12th/sec and 10 to the 12th/sec, respectively. Spectra obtained for the DBC complexes show no evidence of exchange, while those of C222 indicate rapid exchange. It is also noted that the hyperfine splitting constants measured do not change over the 50-K temperature interval studied.

Eastman, M. P.↗

NASA NTRS1979

Observations of emission lines in M supergiants

Copernicus observations of Mg 2 h and k emission lines from M giants and supergiants are described. Supergiants with extensive circumstellar gas shells show an asymmetric k line. The asymmetry is ascribed to superimposed lines of Fe 1 and Mn 1. The Mg 2 line width fit the Wilson-Bappu relation derived from observations of G and K Stars. Results of correlated ground-based observations include (1) the discovery of K 1 fluorescent emission from the Betelgeuse shell; (2) extimates of the mass-loss rates; and (3) the proposal that silicate dust grains must account for the major fraction of the Si atoms in the Betelgeuse shell.

Lambert, D. L.↗

NASA NTRS1980

Heterodyne signal-to-noise ratios in acoustic mode scattering experiments

The relation between the signal to noise ratio (SNR) obtained in heterodyne detection of radiation scattered from acoustic modes in crystalline solids and the scattered spectral density function is studied. It is shown that in addition to the information provided by the measured frequency shifts and line widths, measurement of the SNR provides a determination of the absolute elasto-optical (Pockel's) constants. Examples are given for cubic crystals, and acceptable SNR values are obtained for scattering from thermally excited phonons at 10.6 microns, with no external perturbation of the sample necessary. The results indicate the special advantages of the method for the study of semiconductors.

Cochran, W. R.↗

NASA NTRS1979

Ultraviolet and X-ray observations of Seyfert galaxies and low z QSOs

An analysis of IUE observations of Seyfert galaxies and QSOs indicates that they have the same energy source and heating mechanisms. Neither collisional de-excitation nor simple dust models are sufficient to explain the small L alpha/H beta ratio of Seyfert galaxies and low z QSOs, which is below the recombination value. For Seyfert galaxies, the Log nu (1450) correlates well with Log W lambda (C IV), with a slope similar to that of QSOs. Regarding X-ray fluxes, which were obtained by the A2 experiment onboard the HEAO-1 satellite, the L alpha luminosity correlates well with the continuum luminosity at 1450 A, and there is a positive correlation between the X-ray luminosity and the full line width at zero intensity.

Wu, C.-C.↗

NASA NTRS1979

X-ray spectrometer spectrograph telescope system

A new sounding rocket payload that has been developed for X-ray spectroscopic studies of the solar corona is described. The instrument incorporates a grazing incidence Rowland mounted grating spectrograph and an extreme off-axis paraboloic sector feed system to isolate regions of the sun of order 1 x 10 arc seconds in size. The focal surface of the spectrograph is shared by photographic and photoelectric detection systems, with the latter serving as a part of the rocket pointing system control loop. Fabrication and alignment of the optical system is based on high precision machining and mechanical metrology techniques. The spectrograph has a resolution of 16 milliangstroms and modifications planned for future flights will improve the resolution to 5 milliangstroms, permitting line widths to be measured.

Bruner, E. C., Jr.↗

NASA NTRS1980

Atmospheric opacity in the Schumann-Runge bands and the aeronomic dissociation of water vapor

Knowledge of the aeronomic production of odd hydrogen in the dissociation of water vapor is limited by uncertainties in the penetration of solar irradiance in the Schumann-Runge bands of O2 and by incomplete information concerning the products of photolysis at Lyman alpha. Consideration of all error sources involved in computing the H2O dissociation rate in the wavelength region 175-200 nm leads to an estimated uncertainty of plus or minus 35% at an altitude of 90 km for an overhead sun. The uncertainty increases with decreasing altitude such that the true dissociation rate at 60 km for an overhead sun lies between 0.45 and 1.55 times the results computed using the best input parameters currently available. Calculations of the H2O dissociation rate by Lyman alpha should include the variation in O2 opacity across the solar line width. Neglect of this can lead to errors as large as 50% at altitudes where the process is the major source of odd hydrogen.

Frederick, J. E.↗

NASA NTRS1979

Theoretical performance of multi-layer grid patterns for solar cells

Multilayer grid patterns consist of fine closely spaced grid lines overlaid by coarser patterns of wider and thicker grid lines to collect the current from the finer grids with low series voltage drop and low active-layer sheet losses. An analytical approach leads to closed form solutions with simple relationships between the power losses in the active layer, in the grid and shadowing losses for optimum design proportions. The results show that multilayer grids, with line thickness equal to line width, greatly reduce losses in cell efficiency under concentration conditions of high current collection. (AlGa)As-pn GaAs cells of areas 1-25 sq cm and sheet resistance 40 ohms/square are considered. Also the performance of a n/p GaAs cell of dimensions 10 x 10 cm is studied. With optimized grid patterns high efficiencies are predicted for large area cells.

Flat, A.↗