Search NASA⌕ Search

SEARCH · Search NASA

Results for “Spectral lines”

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.

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

At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Spectral line profiles for a planetary corona

The Lyman and Balmer emission of a planetary corona depend on the exospheric temperature, the integrated column density of solar-illuminated hydrogen, and the region of phase space occupied by particles. Measurements of the intensity alone are incapable of defining the exosphere unambiguously. Line profiles, with high spectral resolution, can show whether a nonthermal component of the escaping hydrogen is present, and can indicate at what altitude satellite orbits of hydrogen atoms are depleted.

Chamberlain, J. W.↗
NASA NTRS1976

Spectral line profiles for a planetary corona

The Lyman and Balmer emissions of a planetary corona depend on the exospheric temperature, the integrated column density of solar-illuminated hydrogen, and the region of phase space occupied by particles. Measurements of the intensity alone are incapable of defining the exosphere unambiguously. Line profiles with high spectral resolution can show whether a nonthermal component of the escaping hydrogen is present and can indicate at what altitude orbits of hydrogen atoms are depleted. It is necessary, however, to plan the observations carefully if they are to be fitted usefully to a model.

Chamberlain, J. W.↗
NASA NTRS2023

The Influence of Line Mixing on the j and k Dependencies of Halfwidths and Temperature Exponents in N2-broadening Coefficients of CH3F Spectral Lines

The N2-broadening halfwidths of CH 3 F in the ν 5 and ν 6 perpendicular bands have been calculated, along with their temperature exponents. These calculations utilize a modified and refined version of the Robert-Bonamy formalism, developed by the current authors within a semi-classical line shape framework. Extensive comparisons between the predicted halfwidths from the model and experimental measurements at 296 K and 183 K are presented. Our latest model accurately predicts the dependencies of the halfwidths on both the j and k quantum numbers. Furthermore, by extending our calculations to two additional temperatures, namely 240 K and 350 K, the temperature exponent N is determined for various sub-branches. The dependencies of N on j and k are analyzed, and theoretical explanations are provided to elucidate the predicted behaviors of N.

Methyl fluoride↗
NASA NTRS1991

M.S.L.A.P. Modular Spectral Line Analysis Program documentation

MSLAP is a software for analyzing spectra, providing the basic structure to identify spectral features, to make quantitative measurements of this features, and to store the measurements for convenient access. MSLAP can be used to measure not only the zeroth moment (equivalent width) of a profile, but also the first and second moments. Optical depths and the corresponding column densities across the profile can be measured as well for sufficiently high resolution data. The software was developed for an interactive, graphical analysis where the computer carries most of the computational and data organizational burden and the investigator is responsible only for all judgement decisions. It employs sophisticated statistical techniques for determining the best polynomial fit to the continuum and for calculating the uncertainties.

Joseph, Charles L.↗
NASA NTRS2024

Sun-as-a-Star Spectral Line Variability in the 300–2390 nm Wavelength Range

Combining the near-daily Ozone Monitoring Instrument (OMI) and Tropospheric Monitoring Instrument (TROPOMI) measurements of solar spectra, we construct line indices (line-core to line-flanks ratios) for various transitions (mainly Fe I) in the 300–2390 nm spectral domain. The indices are supplemented by the wavelength-binned fluxes from OMI and Total and Spectral Solar Irradiance Sensor (TSIS-1). To study the short-term (solar-rotational) patterns, we normalize the indices and fluxes to the minimum-activity epoch, then de-trend them with 81 day running means. Comparisons of the de-trended TSIS-1 and OMI fluxes with the NASA-NOAA-LASP SSI (NNLSSI1) model show excellent agreement, to (0.5–2.2) × 10 -4 in the normalized and de-trended data. The data are subjected to a multiregression analysis against quantities representing the facular brightening and the sunspot darkening. The de-trended line indices and average fluxes show different sensitivities to these two solar magnetic-activity manifestations, with the fluxes being far more susceptible to the sunspot component. The de-trended line indices experience a rapid drop of activity levels towards longer wavelengths, albeit with a large rebound in the short-wave infrared (SWIR) domain that is caused by the ubiquitous, temperature-sensitive CO transitions. The wavelength-dependent activity also falls, however much slower, in the de-trended average fluxes. Qualitatively similar behavior is captured by semiempirical models.

Solar spectral Irradiance↗
NASA NTRS2019

NICER Discovers Spectral Lines During Photospheric Radius Expansion Bursts from 4U 1820-30: Evidence for Burst-Driven Winds

We report the discovery with the Neutron Star Interior Composition Explorer (NICER) of narrow emission and absorption lines during photospheric radius expansion (PRE) X-ray bursts from the ultracompact binary 4U 1820 −30. NICER observed 4U 1820−30 in 2017 August during a low-flux, hard spectral state, accumulating about 60 ks of exposure. Five thermonuclear X-ray bursts were detected, of which four showed clear signs of PRE. We extracted spectra during the PRE phases and fit each to a model that includes a Comptonized component to describe the accretion-driven emission, and a blackbody for the burst thermal radiation. The temperature and spherical emitting radius of the fitted blackbody are used to assess the strength of PRE in each burst. The two strongest PRE bursts (burst pair 1) had blackbody temperatures of ≈0.6 keV and emitting radii of ≈100 km (at a distance of 8.4 kpc). The other two bursts (burst pair 2) had higher temperatures (≈0.67 keV) and smaller radii (≈75 km). All of the PRE bursts show evidence of narrow line emission near 1 keV. By coadding the PRE phase spectra of burst pairs 1 and, separately, 2, we find, in both coadded spectra, significant, narrow, spectral features near 1.0 (emission), 1.7, and 3.0 keV (both in absorption). Remarkably, all the fitted line centroids in the coadded spectrum of burst pair 1 appear systematically blueshifted by a factor of 1.046±0.006 compared to the centroids of pair 2, strongly indicative of a gravitational shift, a wind-induced blueshift, or more likely some combination of both effects. The observed shifts are consistent with this scenario in that the stronger PRE bursts in pair 1 reach larger photospheric radii, and thus have weaker gravitational redshifts, and they generate faster outflows, yielding higher blueshifts. We discuss possible elemental identifications for the observed features in the context of recent burst-driven wind models.

Strohmayer, T. E.↗
NASA NTRS2020

Eta Carinae & the Homunculus: Far Infrared Sub-millimeter Spectral Lines detected with the Herschel Space Observatory

The evolved massive binary star η Carinae underwent eruptive mass loss events that formed the complex bi-polar “Homunculus” nebula harboring tens of solar masses of unusually nitrogen-rich gas and dust. Despite expectations for the presence of a significant molecular component to the gas, detections have been observationally challenged by limited access to the far-infrared and the intense thermal continuum. A spectral survey of the atomic and rotational molecular transitions was carried out with theHerschel Space Observatory, revealing a rich spectrum of broad emission lines originating in the ejecta. Velocity profiles of selected PACS lines correlate well with known substructures: Hi in the central core; NH and weak [Cii] within the Homunculus; and [Nii] emissions in fast-moving structures external to the Homunculus.We have identified transitions from [Oi], Hi, and 18 separate light C- and O-bearing molecules including CO, CH, CH+, and OH, and a wide set of N-bearing molecules,NH, NH+, N2H+, NH2, NH3, HCN, HNC, CN, and N2H+. Half of these are new detections unprecedented for any early-type massive star environment. A very low ratio[12C/13C]≤4 is estimated from five molecules and their isotopologues. We demonstrate that non-LTE effects due to the strong continuum are significant. Abundance patterns are consistent with line formation in regions of carbon and oxygen depletions with nitrogen enhancements, reflecting an evolved state of the erupting star with efficient transport of CNO-processed material to the outer layers. The results offer many opportunities for further observational and theoretical investigations of the molecular chemistry under extreme physical and chemical conditions around massive stars in their final stages of evolution.

T. R. Gull↗
NASA NTRS1992

Factor analysis as a tool for spectral line component separation 21cm emission in the direction of L1780

The spectra of the 21cm HI radiation from the direction of L1780, a small high-galactic latitude dark/molecular cloud, were analyzed by multivariate methods. Factor analysis was performed on HI (21cm) spectra in order to separate the different components responsible for the spectral features. The rotated, orthogonal factors explain the spectra as a sum of radiation from the background (an extended HI emission layer), and from the L1780 dark cloud. The coefficients of the cloud-indicator factors were used to locate the HI 'halo' of the molecular cloud. Our statistically derived 'background' and 'cloud' spectral profiles, as well as the spatial distribution of the HI halo emission distribution were compared to the results of a previous study which used conventional methods analyzing nearly the same data set.

Toth, L. V.↗
NASA NTRS1984

Absolute intensities of spectral lines in carbon dioxide bands near 2050/cm

The absolute intensities of individual lines of eleven relatively weak bands of (C-12)(O-16)2, (C-13)(O-16)2, (O-16)(C-12)(O-18), and (O-16)(C-12)(O-17) near 2050/cm were measured and recorded at room temperature and 0.01/cm resolution with the Fourier transform spectrometer located in the McMath solar telescope complex located at the National Solar Observatory on Kitt Peak. Each spectrum was obtained with an integration time of one hour, the temperature and pressure were monitored during this time, and the signal-to-rms noise in the 5 micron region was approximately 4000 for all scans. The intensities were determined from analysis of 1-2/cm segments of spectra using nonlinear least-squares spectral curve fitting, and analyzed to determine the vibrational band intensity and F-factor coefficients for each of the bands. The results are pertinent to a wide variety of problems in atmospheric physics and for the analysis of remote-sensing data.

Rinsland, C. P.↗