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All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Chemistry and spectroscopy of the Jovian atmosphere

A comprehensive review is given of the chemistry and spectroscopic studies of the Jovian atmosphere. Thermochemical equilibrium models for determining atmospheric composition are considered along with possible disequilibrating processes, and studies of the photochemistry of H2, CH4, NH3, H2S, and PH3 using the modeling methods are summarized. It is shown that photodissociation and advection are the major disequilibrating processes in Jupiter's atmosphere, that lightning and charged-particle bombardment are relatively minor factors in the planet's bulk chemistry, and that the existence of living organisms on the planet is highly improbable. Spectroscopic investigations of Jupiter are discussed, emphasizing recent observations of absorption bands due to CH4, NH3, H2, He, and D. Spectroscopic abundance determinations are examined for H2, HD, CH4, CH3D, NH3, C2H6, C2H2, and PH3. Upper limits are given for the abundances of several unobserved gases in the visible atmosphere, including H2S, HCl, SiH4, benzene, purines, pyrimidines, and their derivatives.

Prinn, R. G.↗
NASA NTRS2001

On Interpreting the Photoelectron Spectra of MgO

The (sup 2)Sigma(+) and (sup 2)Pi states of MgO(-) and the (sup 1)Sigma(+), (sup 1)Pi, and (sup 3)Pi states of MgO are studied using the averaged coupled-pair functional (ACPF) approach. The computed spectroscopic constants are in good agreement with the available experimental data. The computed Franck-Condon factors and photodetachment overlaps are compared with experiment.

Bauschlicher, Charles W., Jr.↗
NASA NTRS2008

The Atmospheric Dynamics of Alpha Tau (K5 III) -- Clues to Understanding the Magnetic Dynamo

Using HST/GHRS, HST/STIS and FUSE archival data for (alpha) Tau and the CHIANTI spectroscopic code, we have derived line shifts, volumetric emission measures, and plasma density estimates, and calculated filling factors for a number of UV lines forming between 10,000 K and 300,000 K in the outer atmosphere of this red giant star. The data suggest the presence of low-temperature extended regions and high-temperature compact regions, associated with magnetically open and closed structures in the stellar atmosphere, respectively. The signatures of UV lines from Alpha Tau can be consistently understood via a model of upward-traveling Alfven waves in a gravitationally stratified atmosphere. These wakes cause non-thermal broadening in UV lines due to unresolved wave motions and downward plasma motions in compact magnetic loops heated by resonant .4lf\en wave heating. We discuss implications of this interpretation for understanding the nature of magnetic dynamos operating in late-type giants.

Carpenter Kenneth G.↗
NASA NTRS2008

The Atmospheric Dynamics of alpha Tau (K5 III) - Clues to Understanding the Magnetic Dynamo in Late-Type Giant Stars

Using HST/GHRS, HST/STIS and FUSE archival data for alpha Tau and the CHIANTI spectroscopic code, we have derived line shifts, volumetric emission measures, and plasma density estimates, and calculated filling factors for a number of UV lines forming between 10,000 K and 300,000 K in the outer atmosphere of this red giant star. The data suggest the presence of low-temperature extended regions and high-temperature compact regions, associated with magnetically open and closed structures in the stellar atmosphere, respectively. The signatures of UV lines from alpha Tau can be consistently understood via a model of upward-traveling Alfven waves in a gravitationally stratified atmosphere. These waves cause non-thermal broadening in UV lines due to unresolved wave motions and downward plasma motions in compact magnetic loops heated by resonant Alfven wave heating.

Carpenter, Kenneth G.↗
NASA NTRS2008

The Atmospheric Dynamics of alpha Tau (K5 III) - Clues to Understanding the Magnetic Dynamo in Late-Type Giant Stars

Using HST/GHRS, HST/STIS and FUSE archival data for alpha Tau and the CHIANTI spectroscopic code, we have derived line shifts, volumetric emission measures, and plasma density estimates, and calculated filling factors for a number of UV lines forming between 10,000 K and 300,000 K in the outer atmosphere of this red giant star. The data suggest the presence of low-temperature extended regions and high-temperature compact regions, associated with magnetically open and closed structures in the stellar atmosphere, respectively. The signatures of UV lines from alpha Tau can be consistently understood via a model of upward-traveling Alfven waves in a gravitationally stratified atmosphere. These waves cause non-thermal broadening in UV lines due to unresolved wave motions and downward plasma motions in compact magnetic loops heated by resonant Alfven wave heating.

Carpenter, Kenneth G.↗
NASA NTRS2010

Field Testing of High Current Electrokinetic Nanoparticle Treatment for Corrosion Mitigation in Reinforced Concrete

Electrokinetic Nanoparticle (EN) treatment was used as a rapid repair measure to mitigate chloride induced corrosion of reinforced concrete in the field. EN treatment uses an electric field to transport positively charged nanoparticles to the reinforcement through the concrete capillary pores. Cylindrical reinforced concrete specimens were batched with 4.5 wt % salt content (based on cement mass). Three distinct electrokinetic treatments were conducted using high current density (up to 5 A/m2) to form a chloride penetration barrier that was established in 5 days, as opposed to the traditional 6-8 weeks, generally required for electrochemical chloride extraction (ECE). These treatments included basic EN treatment, EN with additional calcium treatment, and basic ECE treatment. Field exposures were conducted at the NASA Beachside Corrosion Test Site, Kennedy Space Center, Florida, USA. The specimens were subjected to sea water immersion at the test site as a posttreatment exposure. Following a 30-day post-treatment exposure period, the specimens were subjected to indirect tensile testing to evaluate treatment impact. The EN treated specimens exhibited 60% and 30% increases in tensile strength as compared to the untreated controls and ECE treated specimens respectively. The surfaces of the reinforcement bars of the control specimens were 67% covered by corrosion products. In contrast, the EN treated specimens exhibited corrosion coverage of only 4%. Scanning electron microscopy (SEM) revealed a dense concrete microstructure adjacent to the bars of the treated specimens as compared to the control and ECE specimens. Energy dispersive spectroscopic (EDS) analysis of the polished EN treated specimens showed a reduction in chloride content by a factor of 20 adjacent to the bars. This study demonstrated that EN treatment was successful in forming a chloride penetration barrier rapidly. This work also showed that the chloride barrier was effective when samples were exposed to field conditions at one of the most severely corrosive environments in North America.

Cardenas, Henry↗
NASA NTRS2008

The Atmospheric Dynamics of Alpha Tau (K5 III) - Clues to Understanding the Magnetic Dynamo in Late-Type Giant Stars

Using HST/GHRS, HST/STIS and FUSE archival data for a Tau and the CHIANTI spectroscopic code, we have derived line shifts, volumetric emission measures, and plasma density estimates, and calculated filling factors for a number of UV lines forming between 10,000 K and 300,000 K in the outer atmosphere of this red giant star. The data suggest the presence of low-temperature extended regions and high-temperature compact regions, associated with magnetically open and closed structures in the stellar atmosphere, respectively. The signatures of UV lines from a Tau can be consistently understood via a model of upward-traveling Alfv6n waves in a gravitationally stratified atmosphere. These waves cause nonthermal broadening in UV lines due to unresolved wave motions and downward plasma motions in compact magnetic loops heated by resonant Alfven wave heating.

Carpenter, Kenneth G.↗
NASA NTRS2015

A Photometric Machine-Learning Method to Infer Stellar Metallicity

Following its formation, a star's metal content is one of the few factors that can significantly alter its evolution. Measurements of stellar metallicity ([Fe/H]) typically require a spectrum, but spectroscopic surveys are limited to a few x 10(exp 6) targets; photometric surveys, on the other hand, have detected > 10(exp 9) stars. I present a new machine-learning method to predict [Fe/H] from photometric colors measured by the Sloan Digital Sky Survey (SDSS). The training set consists of approx. 120,000 stars with SDSS photometry and reliable [Fe/H] measurements from the SEGUE Stellar Parameters Pipeline (SSPP). For bright stars (g' < or = 18 mag), with 4500 K < or = Teff < or = 7000 K, corresponding to those with the most reliable SSPP estimates, I find that the model predicts [Fe/H] values with a root-mean-squared-error (RMSE) of approx.0.27 dex. The RMSE from this machine-learning method is similar to the scatter in [Fe/H] measurements from low-resolution spectra..

machine learning↗
DOE OSTI2025

The Power of DESI for Photometric Redshift Calibration: A Case Study with KiDS-1000

Accurate redshift estimates are a critical requirement for weak lensing surveys and one of the main uncertainties in constraints on dark energy and large-scale cosmic structure. In this paper, we study the potential to calibrate photometric redshift (photo-z) distributions for gravitational lensing using the Dark Energy Spectroscopic Instrument (DESI). Since beginning its science operations in 2021, DESI has collected more than 50 million redshifts, adding about one million monthly. In addition to its large-scale structure samples, DESI has also acquired over 256k high-quality spectroscopic redshifts (spec-zs) in the COSMOS and XMM and VVDS fields. This is already a factor of 3 larger than previous spec-z calibration compilations in these two regions. Here, we explore calibrating photo-zs for the subset of KiDS-1000 galaxies that fall into joint self-organizing map (SOM) cells overlapping the DESI COSMOS footprint using the DESI COSMOS observations. Estimating the redshift distribution in KiDS-1000 with the new DESI data, we find broad consistency with previously published results while also detecting differences in the mean redshift in some tomographic bins with an average shifts of Delta Mean(z) = -0.028 in the mean and Delta Median(z) = +0.011 in the median across tomographic bins. However, we also find that incompleteness per SOM cell, i.e., groups of galaxies with similar colors and magnitudes, can modify n(z) distributions. Finally, we comment on the fact that larger photometric catalogs, aligned with the DESI COSMOS and DESI XMM and VVDS footprints, would be needed to fully exploit the DESI dataset and would extend the coverage to nearly eight times the area of existing 9-band photometry.

Blanco, Diana [UC, Santa Cruz; UC, Santa Cruz, Ins↗
NASA NTRS1995

The gaseous extent of galaxies and the origin of Lyman-alpha absorption systems: A survey of galaxies in the fields of Hubble Space Telescope spectroscopic target QSOs

We present initial results of an imaging and spectroscopic survey of faint galaxies in fields of Hubble Space Telescope (HST) spectroscopic target QSOs. The primary objectives of the survey are (1) to determine the incidence, extent, and covering factor of extended gaseous envelopes of luminous galaxies and (2) to determine the fraction of Ly(alpha) absorption systems that arise in luminous galaxies. The goal of the survey is to identify in each field under construction all objects with apparent r-band magnitudes satisfying r less than 21.5 within angular distances to the QSOs satisfying 0 less thyan 1.3'. The current observations cover six fields and are 37% complete to the goal ofthe survey. These observations identify 46 galaxies at redshifts spanning z = 0.0700-0.5526 and at impact parameters to the QSOs spanning rho = 16.6-346.9/h kpc. Of these galaxies, 11 are coincident in redshift with absorption systems and 21 do not give rise to absorption to within sensitive upper limits. Nine galaxies are coincident in redshift with 'Ly(alpha)-forest' absorption systems that show Ly(alpha) absorption but no corresponding metal-line absorption, and two galaxies are coincident in redshift with C IV absorption systems that show both Ly(alpha) and C IV absorption. Various lines of evidence demonstrate that the coincident galaxies are responsible for the corresponding absorption systems and are not present as the result of chance coincidence or merely spatial correlated with the absorption systems. The most important evidence is that there exists a statistical anti-correlation between Ly(aplha) rest-frame equivalent width and the impact parameter. Each of five galaxies with rho = 70-160/h kpc give rise to Ly(alpha) absorption, and just one of nine galaxies with rho greater than 70-160/h kpc gives rise to Ly(alpha) absorption. At least eight of 23 Ly(alpha) absorption systyems arise in galaxies. On the basis of these results we reach the following conclusions: (1) At z less than or approximately = 1 most luminosu galaxies are surrounded by extended gaseous envelopes of approximately = 160/h kpc radius and of roughly unit covering factor. This conclusion confirms previous speculation that normal luminosu galaxies possess extended gaseous halos or extended gaseous disks. (2) At z less than or approximately = 1 the fraction of Ly(aplha) absorption systems-including Ly(alpha)-forest absorption systems-that arise in luminous galaxies is at least 0.32 +/- 0.10 and may be as high as 0.60 +/- 0.19. This conclusion runs contrary to the longstanding belief that Ly(alpha)-forest absorption systems arise in intergalactic clouds.

Lanzetta, Kenneth M.↗
DOE OSTI2026

Operando Spectroscopic Analysis of Photovoltage Generation in Hematite Photoanodes

Solar-driven water splitting requires sufficient photovoltage to drive both water oxidation and proton reduction. Understanding the factors driving and limiting photovoltage generation is therefore crucial to optimizing photoelectrode design but has proven challenging to determine under operando conditions for photoanodes driving slow multiredox reactions such as water oxidation. In this work, operando optical spectroscopy is employed to measure the hole quasi-Fermi level (E F,p ) position in model hematite photoanodes as a function of applied bias and light intensity. The quasi-Fermi level splitting determined from these data are shown be in excellent agreement with the directly measured photovoltages, demonstrating the primarily electrochemical rather than primarily electrostatic origin of photovoltage in these photoelectrodes. E F,p pinning is observed at low light intensities and biases, indicative of hole trap states lying ∼0.2 eV above the valence band edge with a density of ∼1 nm −2 . Hole accumulation in these trap states is correlated with first order water oxidation. At higher light intensities and/or more anodic bias, E F,p becomes unpinned, assigned to saturation of these trap states, and correlated with the onset of third order water oxidation to molecular oxygen. Comparison with rate law analyses for other photoanodes indicates that such hole trap states may be a ubiquitous feature of metal oxides and suggests that materials processing strategies to suppress the density of such states would be a promising strategy to enhance photoanode performance.

Hematite↗
DOE OSTI2026

Gepta-EX: a multi-channel germanium detector for X-ray absorption fine structure

Fluorescence-mode X-ray absorption spectroscopy (XAS) at high photon energies requires detectors with high stopping power and excellent energy resolution to measure weak element-specific signals. Traditional silicon-based detectors suffer from poor efficiency above ∼20 keV, while most high-Z materials such as cadmium telluride, cadmium zinc telluride, and gallium arsenide have focused predominantly on imaging applications with limited spectroscopic resolution. In contrast, germanium combines excellent stopping power with superior intrinsic energy resolution due to its low Fano factor and favorable charge transport properties, making it ideal for high-resolution spectroscopy in the 15 keV to 100 keV range. To address these requirements, we report on the development, fabrication, and performance evaluation of Gepta-EX, a compact multi-channel high-purity germanium (HPGe) detector system for fluorescence-mode XAS. The Gepta-EX system features a monolithic seven-channel HPGe pixel array integrated with low-noise CUBE charge-sensitive preamplifiers, housed within a thermally isolated compact cryostat operating near 90 K. The detector achieves energy resolutions of 218 eV at 5.9 keV (from a 55 Fe source) and 373 eV at 59.5 keV (from a 241 Am source), with uniform performance across all channels. By avoiding the escape peak interference commonly associated with silicon detectors and providing stable, high-resolution performance, Gepta-EX represents a powerful tool for high-energy X-ray spectroscopy.

36 MATERIALS SCIENCE↗
DOE OSTI2025

DESI peculiar velocity survey – Fundamental Plane

The Dark Energy Spectroscopic Instrument (DESI) peculiar velocity survey aims to measure the peculiar velocities of early- and late-type galaxies within the DESI footprint using both the Fundamental Plane and optical Tully–Fisher relations. Direct measurements of peculiar velocities can significantly improve constraints on the growth rate of structure, reducing uncertainty by a factor of approximately 2.5 at redshift 0.1 compared to the DESI Bright Galaxy Survey’s redshift space distortion measurements alone. We assess the quality of stellar velocity dispersion measurements from DESI spectroscopic data. These measurements, along with photometric data from the Legacy Survey, establish the Fundamental Plane relation and determine distances and peculiar velocities of early-type galaxies. During survey validation, we obtain spectra for 6698 unique early-type galaxies, up to a photometric redshift of 0.15. 64 per cent of observed galaxies (4267) have relative velocity dispersion errors below 10 per cent. This percentage increases to 75 per cent if we restrict our sample to galaxies with spectroscopic redshifts below 0.1. We use the measured central velocity dispersion, along with photometry from the DESI Legacy Imaging Surveys, to fit the Fundamental Plane parameters using a 3D Gaussian maximum likelihood algorithm that accounts for measurement uncertainties and selection cuts. In addition, we conduct zero-point calibration using the absolute distance measurements to the Coma cluster, leading to a value of the Hubble constant, H 0 = 76.05 ± 0.35 (statistical) ±0.49 (systematic Fundamental Plane) ±4.86 (statistical due to calibration) km s –1 Mpc –1 ⁠. This H 0 value is within 2σ of Planck cosmic microwave background results and within 1σ of other low-redshift distance indicator-based measurements.

cosmological parameters↗
DOE OSTI2025

Physics-driven Explosions of Stripped High-mass Stars: Synthetic Light Curves and Spectra of Stripped-envelope Supernovae with Broad Light Curves

Stripped-envelope supernovae (SESNe) represent a significant fraction of core-collapse supernovae, arising from massive stars that have shed their hydrogen and, in some cases, helium envelopes. The origins and explosion mechanisms of SESNe remain a topic of active investigation. In this work, we employ radiative-transfer simulations to model the light curves and spectra of a set of explosions of single, solar-metallicity, massive Wolf–Rayet stars with ejecta masses ranging from 4 to 11 M ⊙ , which were computed from a turbulence-aided and neutrino-driven explosion mechanism. We analyze these synthetic observables to explore the impact of varying ejecta mass and helium content on observable features. We find that the light curve shape of these progenitors with high ejecta masses is consistent with observed SESNe with broad light curves but not the peak luminosities. The commonly used analytic formula based on rising bolometric light curves overestimates the ejecta mass of these high-initial-mass progenitor explosions by a factor of up to 2.6. In contrast, the calibrated method by Haynie et al., which relies on late-time decay tails, reduces uncertainties to an average of 20% within the calibrated ejecta mass range. Spectroscopically, the He I 1.083 μm line remains prominent even in models with as little as 0.02 M ⊙ of helium. However, the strength of the optical He I lines is not directly proportional to the helium mass but instead depends on a complex interplay of factors such as the 56 Ni distribution, composition, and radiation field. Thus, producing realistic helium features requires detailed radiative transfer simulations for each new hydrodynamic model.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

The Stellar Mass Function for Nine Massive Galaxy Clusters in the Local Universe

We measure galaxy stellar mass functions (SMFs) for nine of the most massive galaxy clusters in the local Universe (0.07 < z < 0.11) using deep and complete spectroscopy from the MAssive Cluster Survey with Hectospec (MACH). We construct the cluster SMFs down to log (M * /M ⊙ ) ≳ 8.5. For comparison, we measure the SMF for field galaxies, complete to log (M * /M ⊙ ) ≳ 10.5, based on Sloan Digital Sky Survey spectroscopy over the same redshift range. The mean MACH SMF shows a shape similar to that of the field SMF but with a significantly higher amplitude at log (M * /M ⊙ ) < 11.4. At log (M * /M ⊙ ) > 11.4, the MACH SMF shows a clear excess, indicating the contribution of massive galaxies, including brightest cluster galaxies (BCGs). Based on homogeneous MACH spectroscopy, we compare SMF shapes for quiescent and star-forming members as a function of the cluster-centric distance. The quiescent SMFs display a curved shape with a peak at log (M * /M ⊙ ) ≈ 10.5; the star-forming SMFs decline monotonically with increasing stellar mass. We further compare the mean MACH SMF with SMFs derived from similarly massive clusters in the IllustrisTNG-300 simulations. The shape of the observed and simulated SMFs agrees well overall. However, the MACH clusters contain roughly a factor of 2 more galaxies at 9.0 < log (M * /M ⊙ ) < 10.5. These results demonstrate that constructing cluster SMFs from complete spectroscopic samples can test simulations and provide powerful constraints on galaxy formation and evolution in dense environments.

Park, Jong-In [Seoul National University (Korea, R↗
NASA NTRS1990

A composition comparison between comets P/Halley and P/Brorsen-Metcalf

The appearance of comet Brorsen-Metcalf in 1989 following only a few years on the heels of comet Halley in 1986 gave an unusual opportunity to compare two comets of similar orbital elements but potentially different physical and chemical characteristics. Photometric spectral data were acquired for Brorsen-Metcalf on two dates: 13 July 1989 and 2 August 1989. The observations were performed with the 154 cm Catalina Telescope of the University of Arizona Observatories. The spectrum for 13 July 1989 is compared to a Halley spectrum. The general appearance of the spectra is very similar, both comets showing emission due to C2, NH2, OI(D-1), and CN. Neither displays any emission features that are exclusive to only one of the two. Since water is now reasonably well established as the major driving force in the activity of a comet, the H2O production rate for comet Brorsen-Metcalf was calculated. The relative ratios between the production rates of the various species obtained from the data are presented. Results are summarized in tabular form. All species are compared to the H2O production rate of the two comets. The results indicate that C2 originates from an extended source of dust particles or small polymers in addition to parent molecules. The lower production rates of C2 and CN in Brorsen-Metcalf correlate well with both the lower dust production and their smaller increase as the comet approaches the sun. Even without a mode, the spectroscopic observations of Brorsen-Metcalf allowed significant compositional conclusions to be drawn. The NH2 abundance is lower by about a factor of three which appears to be independent of heliocentric distance. Both C2 and CN are less abundant in Brorsen-Metcalf than in Halley and do not seem to participate as much in the strong increase as the comet approaches the sun. The lower H2O production rate implies that the active surface area of the comet Brorsen-Metcalf is much smaller, or equivalently the comet as a whole is much smaller. The substantially lower continuum level for Brorsen-Metcalf cannot readily be explained by smaller or larger active surface area, and must be intrinsic to the comet's embedded dust-to-ice ratio, or to an overall smaller-sized dust grain population.

Disanti, Michael A.↗
NASA NTRS2003

The Constellation-X Observatory

The Constellation X-ray mission will revolutionize X-ray spectroscopy and will provide a key component of NASA's '!Beyond Einstein" program. Over the past 35 years, X-ray astronomy has grown from infancy to near-maturity and is now an indispensable astrophysical tool. Constellation-X will transform this field from the exploratory spectroscopic era of Chandra and XMM to an era of fully comprehensive spectroscopic studies. The mission will consist of four 1.6-meter X-ray telescopes orbiting the Earth/Sun system. By providing a factor of 100 increase in throughput over previous missions, as well as high spectral resolution and a broad energy bandpass, Constellation-X will obtain high quality spectra for all classes of X-ray sources over a wide range of luminosity and redshift. It will study the warping of space and time near black holes, determine the distribution of ordinary matter, dark matter and dark energy, and probe detailed physical processes that occur at temperatures, densities and pressures far beyond those achievable in Earth-bound laboratories.

Weaver, Kimberly↗