Search NASA⌕ Search

SEARCH · Search NASA

Results for “Line Positions”

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 NTRS2022

Ames-2021 CO 2 Dipole Moment Surface and IR Line Lists: Toward 0.1% Uncertainty for CO 2 IR Intensities

A highly accurate CO 2 ab initio dipole moment surface (DMS), Ames-2021, is reported along with 12 C 16 O 2 infrared (IR) intensity comparisons approaching a 1–4‰ level of agreement and uncertainty. The Ames-2021 DMS was accurately fitted from CCSD(T) finite-field dipoles computed with the aug-cc-pVXZ (X = T, Q, 5) basis for C atom and the d-aug-cc-pVXZ (X = T, Q, 5) basis for O atoms, and extrapolated to the one particle basis set limit. Fitting σ(rms) is 3.8 × 10^(–7) au for 4443 geometries below 15 000 per cm . The corresponding IR intensity, S Ames-2021 , are computed using the Ames-2 potential energy surface (PES), which is the best PES available for CO 2 . Compared to high accuracy IR studies for 2001i–00001 and 3001i–00001 bands, S Ames-2021 matches NIST experiment-based intensities [S NIST-HIT16 or S HIT20 ] to −1.0 ± 1.3‰, or matches DLR experiment-based intensities [S DLR-HIT16/UCL/Ames ] to 1.9 ± 3.7‰. This indicates the systematic deviations and uncertainties have been significantly reduced in S Ames-2021 . The S UCL2015 (or S HITRAN2016 ) have larger deviations (vs S DLR ) and uncertainties (vs S DLR , S NIST ) which are attributed to the less accurate Ames-1 PES adopted in UCL-296 line list calculation. The S Ames-2021 intensity of 12 C 16 O 2 and 13 C 16 O 2 is utilized to derive new absolute 13 C/ 12 C ratios for Vienna PeeDee Belemnite (VPDB) with uncertainty reduced by 1/3 or 2/3. Further evaluation of S Ames-2021 are carried out on those CO 2 bands discussed in the HITRAN2020 update paper. Consistent improvements and better accuracies are found in band-by-band analysis, except for those bands strongly affected by Coriolis couplings, or very weak bands measured with relatively larger experimental uncertainties. The Ames-2021 296 K IR line lists are generated for 13 CO 2 isotopologues, with 18,000 per and S 296K > 1E–31) cm/molecule cutoff and then combined with CDSD line positions (except 14 C 16 O 2 ). The Ames-2021 DMS and 296 K IR line lists represent a major improvement over previous CO 2 theoretical IR intensity studies, including Ames-2016, UCL-296, and recent UCL DMS 2021 update. A real 1 permille level of agreement and uncertainty will definitely require both more accurate PES and more accurate DMS.

Chemical calculations↗
NASA NTRS1991

nu-2 band of H2 O-16 - Line strengths and transition frequencies

High-resolution spectra of H2 O-16 were recorded with a Fourier-transform spectrometer covering transitions in the (010)-(000) band from 1066 to 2582/cm. The measured line frequencies were used along with additional data taken from studies at microwave and far-infrared frequencies in an analysis to obtain rotational energies of levels in the (000) and (010) states. Measurements of the line strengths were fitted by least squares to a model in which the dipole moment matrix elements were represented by as many as 19 expansion coefficients. The results produced computed line strength values that are in excellent agreement, on the average, with the 874 experimental transitions included in the analysis. These results provide a more accurate representation of the line positions and strengths for the (010)-(000) band than are currently available on the HITRAN absorption line parameter compilation.

Toth, Robert A.↗
NASA NTRSDate not supplied

Reliable IR Line Lists for N2O and OCS Isotopologues for High Temperature Applications up to 2000 K

To address the needs of planetary and exoplanetary atmosphere studies towards JWST, HWO and future IR astronomy missions, theoretical IR line lists of Carbonyl Sulfide (OCS) and Nitrous Oxide (N2O) are generated to provide complete, reliable, and consistent IR reference data in the range of 0 - 15,000 cm-1, or wavelength longer than 0.67 Å, for temperature up to 2000 K. The line lists are quantum mechanically computed using spectroscopically accurate potential energy surfaces empirically refined with reliable high-resolution experimental data, and high-quality dipole moment surfaces constructed at CCSD(T) level with aug-cc-pVT/Q/5(+d)Z basis and extrapolations to complete basis set limit. The Ames N2O line list includes the primary isotopologue 14N2 16O (denoted "446") with J=0-210 and E' up to 25,000 cm-1, and 11 minor isotopologues of 15N and 17/18O with J=0-150 and lower E' cutoffs. For OCS, Ames "natural" 296 K line list includes 12 most abundant isotopologues. The intensity contribution of OCS minor isotopologues at higher temperature is non-negligible, e.g., 8.6 ± 4.9% at 1000 K. The 16O12C32S (93.7%) and 16O12C34S (4.2%) transitions are computed with J=0-240 and E'< 22,000 cm-1, plus J=0-150 and E' < 16,000 cm-1 for five more minor isotopologues. Reliable Effective Hamiltonian models (e.g., NOSL-296 for 14N2 16O), experimental data collections, and reliable HITRAN or MARVEL levels are combined with quantum rovibrational calculations to deliver accurate and consistent empirical corrections for line positions. The reliability and accuracy of our IR intensity predictions are demonstrated by comparison with available databases, line lists, and experiments, at both room temperature and at high temperature. The line lists will be freely available to public online at ZENODO and NAS data portal. We acknowledge the financial support from NASA XRP and APRA programs.

Planetary↗
NASA NTRS1980

Quantitative laboratory spectra and spectral line parameters for the nu2 and nu4 bands of PH3 applicable to spectral radiative models of the atmosphere of Jupiter

Quantitative laboratory PH3 absorption spectra were obtained in the 800-1350/cm region, at approximately 0.05/cm resolution, with gas amounts corresponding to observed PH3 absorptions in the atmosphere of Jupiter. A compilation of spectral line positions, intensities and ground state energies has been generated for the nu2 and nu4 bands of PH3. Line-by-line calculations have been compared with the experimental spectra.

Goldman, A.↗
NASA NTRS1976

Coordinated ATS 5 electron flux and simultaneous auroral observations

An attempt is made to correlate ATS 5 plasma data with all-sky photographic data taken at Thompson and Gillam, Manitoba. The fields of view of the Canadian stations cover the projected field line position of the satellite. Trapped electron fluxes at the satellite and the simultaneously measured auroral activity near the projected foot of the satellite field line were compared for several days of varying substorm activity with all-sky camera data, which was in the form of time-varying luminosity plots. The observed auroral intensification coincident with plasma injection shows that on a broad scale the auroras are correlated well with the magnetospheric trapped plasma; however, there is a lack of detailed correlation between the fine structure of the trapped plasma fluxes and the small scale auroral features.

Mende, S. B.↗
NASA NTRS2011

The Atmospheres of Titan and Saturn in the Infrared from Cassini: The Interplay Between Observation and Laboratory Studies

The Composite Infrared Spectrometer (CIRS) aboard the Cassini spacecraft has been recording spectra of Saturn and Titan since its arrival in the Saturn system in 2004. CIRS, a Fourier transform spectrometer, observes the thermal infrared spectrum of both atmospheres from 10 to 1500/cm with resolutions up to 0.5/cm (Flasar et al. 2004). From these data CIRS provides global coverage of the molecular composition of the stratosphere and troposphere, as well as maps of temperature and winds. From such studies CIRS helps reveal the chemistry and evolutionary history of Saturn and Titan and their relationships to other Solar System bodies. The Cassini mission is continuing until 2017, permitting CIRS to search for atmospheric changes during more than a Saturnian season. By combining with results from Voyager (1980, 1981) the baseline becomes more than one Saturnian year (Coustenis et al. 2011). CIRS spectroscopy of the atmospheres of Saturn and Titan has raised a variety of questions that require new laboratory studies. A complete understanding of the CIRS high-resolution atmospheric spectra cannot be fully achieved without new or improved line positions and intensities for some trace molecules (e.g., Nixon et al. 2009). Isotopic variants of some of the more abundant species often need improved line parameters in order to derive isotopic ratios (e.g., Coustenis et al. 2008 and Fletcher et a!. 2009). Isotopic ratios contain information about the history of an atmosphere if experimental fractionation rates are available (Jennings et al. 2009). Some aerosol and haze features continue to defy identification and will not be explained without better knowledge of how these materials are formed and until we obtain their laboratory spectra. The interaction between CIRS investigations and laboratory research has been productive and has already led to new discoveries.

Jennings, D. E.↗
NASA NTRS1978

Theoretical simulation of solar spectra in the middle ultraviolet and visible for atmospheric trace constituent measurements

Two balloon flights reaching float altitudes of approximately 30 and 40 km respectively, were used to obtain scans of the ultraviolet and visible solar spectra. Both flights covered the UV (2800-3500A) at approximately 0.3A resolution and the visible at approximately 0.6A. Numerous scans were obtained during ascent and from float for both flights. All spectral scans obtained at float, from high sun to low sun, were calibrated in wavelength by using several standard solar spectra for line position references. Comparisons of low sun scans and high sun scans show significant atmospheric continuum extinction and have the potential of being used to identify atmospheric lines superimposed on the attenuated solar spectrum. The resolution was mathematically degraded to approximately 5A to better see the broad band atmospheric extinction. This low resolution is also appropriate for the available low resolution absorption coefficients of NO2 and O3, allowing the identification of NO2 and O3 features on the sunset spectra.

Goldman, A.↗
NASA NTRS2000

High Resolution Spectroscopy to Support Atmospheric Measurements

The major research activities performed during the cooperative agreement enhanced our spectroscopic knowledge of molecules of atmospheric interest such as carbon dioxide, water vapor, ozone, methane, and carbon monoxide, to name a few. Measurements were made using the NASA Langley Tunable Diode Laser Spectrometer System (TDL) and several Fourier Transform Spectrometer Systems (FTS) around the globe. The results from these studies made remarkable improvements in the line positions and intensities for several molecules, particularly ozone and carbon dioxide in the 2 to 17-micrometer spectral region. Measurements of pressure broadening and pressure induced line shift coefficients and the temperature dependence of pressure broadening and pressure induced line shift coefficients for infrared transitions of ozone, methane, and water vapor were also performed. Results from these studies have been used for retrievals of stratospheric gas concentration profiles from data collected by several Upper Atmospheric Research satellite (UARS) infrared instruments as well as in the analysis of high resolution atmospheric spectra such as those acquired by space-based, ground-based, and various balloon-and aircraft-borne experiments. Our results made significant contributions in several updates of the HITRAN (HIgh resolution TRANsmission) spectral line parameters database. This database enjoys worldwide recognition in research involving diversified scientific fields.

Benner, D. Chris↗
NASA NTRS2000

High Resolution Spectroscopy to Support Atmospheric Measurements

The major research activities performed during the cooperative agreement enhanced our spectroscopic knowledge of molecules of atmospheric interest such as carbon dioxide, water vapor, ozone, methane, and carbon monoxide, to name a few. Measurements were made using the NASA Langley Tunable Diode Laser Spectrometer System (TDL) and several Fourier Transform Spectrometer Systems (FTS) around the globe. The results from these studies made remarkable improvements in the line positions and intensities for several molecules, particularly ozone and carbon dioxide in the 2 to 17-micrometer spectral region. Measurements of pressure broadening and pressure induced line shift coefficients and the temperature dependence of pressure broadening and pressure induced line shift coefficients for infrared transitions of ozone, methane, and water vapor were also performed. Results from these studies have been used for retrievals of stratospheric gas concentration profiles from data collected by several Upper Atmospheric Research satellite (UARS) infrared instruments as well as in the analysis of high resolution atmospheric spectra such as those acquired by space-based, ground-based, and various balloon- and aircraft-borne experiments. Our results made significant contributions in several updates of the HITRAN (HIgh resolution TRANsmission) spectral line parameters database. This database enjoys worldwide recognition in research involving diversified scientific fields.

Benner, D. Chris↗
NASA NTRS1999

Waves in Radial Gravity Using Magnetic Fluid

Terrestrial laboratory experiments studying various fluid dynamical processes are constrained, by being in an Earth laboratory, to have a gravitational body force which is uniform and unidirectional. Therefore fluid free-surfaces are horizontal and flat. Such free surfaces must have a vertical solid boundary to keep the fluid from spreading horizontally along a gravitational potential surface. In atmospheric, oceanic, or stellar fluid flows that have a horizontal scale of about one-tenth the body radius or larger, sphericity is important in the dynamics. Further, fluids in spherical geometry can cover an entire domain without any sidewall effects, i.e. have truly periodic boundary conditions. We describe spherical body-force laboratory experiments using ferrofluid. Ferrofluids are dilute suspensions of magnetic dipoles, for example magnetite particles of order 10 nm diameter, suspended in a carrier fluid. Ferrofluids are subject to an additional body force in the presence of an applied magnetic field gradient. We use this body force to conduct laboratory experiments in spherical geometry. The present study is a laboratory technique improvement. The apparatus is cylindrically axisymmetric. A cylindrical ceramic magnet is embedded in a smooth, solid, spherical PVC ball. The geopotential field and its gradient, the body force, were made nearly spherical by careful choice of magnet height-to-diameter ratio and magnet size relative to the PVC ball size. Terrestrial gravity is eliminated from the dynamics by immersing the "planet" and its ferrofluid "ocean" in an immiscible silicone oil/freon mixture of the same density. Thus the earth gravity is removed from the dynamics of the ferrofluid/oil interface and the only dynamically active force there is the radial magnetic gravity. The entire apparatus can rotate, and waves are forced on the ferrofluid surface by exterior magnets. The biggest improvement in technique is in the wave visualization. Fluorescing dye is added to the oil/freon mixture and an argon ion laser generates a horizontal light that can be scanned vertically. Viewed from above, the experiment is a black circle with wave deformations surrounded by a light background. A contour of the image intensity at any light sheet position gives the surface of the ferrofluid "ocean" at that "latitude". Radial displacements of the waves as a function of longitude are obtained by subtracting the contour line positions from a no-motion contour at that laser sheet latitude. The experiments are run by traversing the forcing magnet with the laser sheet height fixed and images are frame grabbed to obtain a time-series at one latitude. The experiment is then re-run with another laser-sheet height to generate a full picture of the three-dimensional wave structure in the upper hemisphere of the ball as a function of time. We concentrate here on results of laboratory studies of waves that are important in Earth's atmosphere and especially the ocean. To get oceanic scaling in the laboratory, the experiment must rotate rapidly (4-second rotation period) so that the wave speed is slow compared to the planetary rotation speed as in the ocean. In the Pacific Ocean, eastward propagating Kelvin waves eventually run into the South American coast. Theory predicts that some of the wave energy should scatter into coastal-trapped Kelvin waves that propagate north and south along the coast. Some of this coastal wave energy might then scatter into mid-latitude Rossby waves that propagate back westward. Satellite observations of the Pacific Ocean sea-surface temperature and height seem to show signatures of westward propagating mid-latitude Rossby waves, 5 to 10 years after the 1982-83 El Nino. The observational data is difficult to interpret unambiguously owing to the large range of motions that fill the ocean at shorter timescales. This series of reflections giving eastward, north- ward, and then westward traveling waves is observed cleanly in the laboratory experiments, confirming the theoretical expectations.

Ohlsen, D. R.↗
NASA NTRS2016

Ames S-32 O-16 O-18 Line List for High-Resolution Experimental IR Analysis

By comparing to the most recent experimental data and spectra of the SO2 628 ν1/ν3 bands (see Ulenikov et al., JQSRT 168 (2016) 29-39), this study illustrates the reliability and accuracy of the Ames-296K SO2 line list, which is accurate enough to facilitate such high-resolution spectroscopic analysis. The SO2 628 IR line list is computed on a recently improved potential energy surface (PES) refinement, denoted Ames-Pre2, and the published purely ab initio CCSD(T)/aug-cc-pVQZ dipole moment surface. Progress has been made in both energy level convergence and rovibrational quantum number assignments agreeing with laboratory analysis models. The accuracy of the computed 628 energy levels and line list is similar to what has been achieved and reported for SO2 626 and 646, i.e. 0.01-0.03 cm(exp −1) for bands up to 5500 cm(exp −1). During the comparison, we found some discrepancies in addition to overall good agreements. The three-IR-list based feature-by-feature analysis in a 0.25 cm(exp −1) spectral window clearly demonstrates the power of the current Ames line lists with new assignments, correction of some errors, and intensity contributions from varied sources including other isotopologues. We are inclined to attribute part of detected discrepancies to an incomplete experimental analysis and missing intensity in the model. With complete line position, intensity, and rovibrational quantum numbers determined at 296 K, spectroscopic analysis is significantly facilitated especially for a spectral range exhibiting such an unusually high density of lines. The computed 628 rovibrational levels and line list are accurate enough to provide alternatives for the missing bands or suspicious assignments, as well as helpful to identify these isotopologues in various celestial environments. The next step will be to revisit the SO2 828 and 646 spectral analyses.

Sulfur dioxide↗
NASA NTRS1985

A measurement of the vibrational band strength for the upsilon sub 3 band of the HO2 radical

The HO2 radicals generated in a discharge-flow system were observed with tunable diode laser absorption in the P-branch of the nu(3) vibrationall band at 1080/cm. The observed line positions agree with those calculated from the molecular constants for the nu(3) bland obtained from a previous study using laser magnetic resonance spectroscopy. The band strength was determined by observing line center absoptions when HO2 is produced in the reaction F + H2O2 yields HO2 + HF (k1) with a measured concentration of atomic fluorine and excess hydrogen peroxide. F-atom concentrations are measured by diode laser absorption of the spin-orbit transition at 404/cm. The analysis accounts for HO2 losses due to the reactions of HO2 + HO2 yields H2O2 + O2 (k3) and F + HO2 yields HF + O2 (k4). The line strength for the 6(15) 7(16) F(1) transition is 2.9 x 10 to the 21st power sq cm/molecule/cm which corresponds to a nu(3) band strength of 34 +/- 9 sq/cm(STP atm). This value is a factor of 6 lower than previous ab initio calculations. These results will be useful in assessing the feasibility of atmospheric measurements of HO2 using infrared absorption techniques.

Zahniser, M. S.↗
NASA NTRS1990

High resolution infrared spectroscopy of planetary molecules using diode lasers and Fourier transform spectrometers

Modern observations of infrared molecular lines in planets are performed at spectral resolutions which are as high as those available in the laboratory. Analysis of such data requires laboratory measurements at the highest possible resolution, which also yield accurate line positions and intensities. For planetary purposes the spectrometer must be coupled to sample cells which can be reduced in temperature and varied in pressure. An approach which produces the full range of required molecular line parameters uses a combination of tunable diode lasers and Fourier transform spectrometers (FTS). The FTS provides board spectral coverage and good calibration accuracy, while the diode laser can be used to study those regions which are not resolved by the FTS.

Jennings, Donald E.↗
NASA NTRS1980

Analysis of solar spectra in the middle ultraviolet and visible for atmospheric trace constituents measurements

Individual spectral line parameters including line positions, strengths, and intensities were generated for the sq Alpha Sigma - sq Chi Pi (0,0) band of OH, applicable to atmospheric and high temperatures. Energy levels and transition frequencies are calculated by numerically diagonalizing the Hamiltonian. Line strengths are calculated using the dipole matrix and eigenvectors derived from energy matrix diagonalization. The line strengths are compared to those calculated from previously published algebraic line strength formulas. Tables of line parameters are presented for 240 K and 4600 K.

Goldman, A.↗
NASA NTRS2017

Decoupled Magnetoquasistatic Non-Line-of-Sight Position and Orientation Sensing for Arbitrary Distances

Methods and systems for non-line-of-sight positioning are disclosed for arbitrarily short to long ranges, where positioning is achieved using a single anchor not requiring tri-/multi-lateration or tri-/multi-angulation. Magnetoquasistatic fields can be used to determine position and orientation of a device in two or three dimensions. Two or three axis coils can be used in receivers and transmitters. The magnetoquasistatic equations are solved in different scenarios, taking into consideration the image signals originating from the interaction between the fields and ground/earth.

Arumugam, Darmindra D.↗
NASA NTRS1991

Herman-Wallis factors in the C2H2nu5 infrared fundamental near 14 microns

The presence of acetylene has been confirmed for some time in the atmospheres of the outer planets Jupiter, Saturn, Neptune, and Saturn's satellite Titan. For these atmospheres, the determination of C2H2 abundances using its strong nu5 fundamental requires laboratory line position and intensity measurements. The 1-m Fourier transform spectrometer at McMath solar telescope of Kitt Peak National Observatory was used to measure C2H2 at an unapodized spectral resolution of 0.0025/cm. Synthetic spectra are generated by convolving a Voigt line shape with an instrument function and varying intensity parameters by means of a nonlinear least squares technique. Intensities of 37 nu5 lines spanning P18 through R20 were measured using 0.123 torr of gas in a 1-cm cell. A Herman-Wallis intensity correction parameter of 1.3(4) x 10 to the -3rd has been derived using a least squares linear fit.

Maguire, William C.↗
NASA NTRS1983

The 12 micron band of ethane: A spectral catalog from 765 cm(-1) to 900 cm(-1)

The high resolution laboratory absorption spectrum of the 12 micro band of ethane gas is studied. The data were obtained using the McMath Solar Telescope 1 meter Fourier Transform interferometer at Kitt Peak National Observatory and tunable diode laser spectrometers at the University of Tennessee and NASA/Goddard Space Flight Center. Over 200 individual vibration rotation transitions were analyzed taking into account many higher order effects including torsional splitting. Line positions were reproduced to better than 0.001/cm. Both ground and upper state molecular constants were determined in the analysis. The experimental details, the analysis procedures and the results are addressed. A list of ethane transitions occurring near (14)CO2 laser lines needed for heterodyne searches for C2H6 in extraterrestrial sources is also included. A spectral catalog of the ethane nu sub g fundamental from 765/cm to 900/cm is provided. A high dispersion (1/cm 12 in.) plot of both the Kitt Peak interferometric data and a simulated spectrum with Doppler limited resolution, a table of over 8500 calculated transitions listed quantum number assignments, frequencies and intensities are provided.

Atakan, A. K.↗