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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

CS multitransitional study of density distribution in star-forming regions. 2: The S140 region

The S140 molecular cloud was observed in five transitions of CS with resolutions of 11 to 45 arcsec. The data were analyzed with both the LVG and microturbulent models of radiative transfer to derive the density structure. It was found that the CS emission comes from three components of gas: a spherical component centered on the infrared cluster, an arc component along the ionization front between the S140 H II region and the dense molecular cloud core, and a high-velocity component from the dense part of a molecular outflow. The spherical component contributes most to the CS emission and was analyzed in more detail than the other components. Using a temperature distribution derived from an analysis of the dust emission from S140, we fit a power-law density distribution of n(r) = n(sub i)(r/r(sub i))(exp -alpha) to the spherical component. The best fit was for n(sub i) = 1.4 x 10(exp 6) (density at r(sub i) = 0.026 pc) and alpha = 0.8. The density (n(sub i)) was found to be greater than or equal to the density required to account for the dust emission, depending on the dust opacity laws adopted. The presence of optical emission (Dinerstein, Lester, & Rank 1979) suggests a clumpy structure for the dense gas. Considerations of the virial mass and the lowest amount of column density required to produce dust emission put the volume filling factor (f(sub nu)) of the dense gas at approximately 0.14-0.5. We compared S140 with other regions of star formation where the density structure has been derived from excitation analysis. Source-source variations in density gradients and clumpiness clearly exist, ranging from alpha = 2 and f(sub nu) approximately 1 in B335 to alpha approximately 0, f(sub nu) approximately 0.1 in M17. There is a tendency for more massive star-forming regions to have a flatter density distribution, a more clumpy structure, and a large number of young stars. The implications of this tendency are discussed.

Zhou, Shudong↗
NASA NTRS2001

Tentative Identification of Interstellar CS by UV Absorption in the C-X Transition

Current chemical models of translucent clouds imply that sulfur is depleted with respect to its average abundance in diffuse clouds as determined by Morton (1975 ApJ,197, 85) by factors exceeding 10. Existing gigahertz emission observations yield sizable uncertainties in the column densities to background stars, and attempts to measure column densities of CS in the lines-of-sight to various stars through the absorption in the A-X (0,0) electronic transition near 257.6 nm have been unsuccessful. CS dissociates primarily through discrete absorptions into predissociating states. In analogy with CO the strongest of these is the C-X band found near 140.0 nm. We report the tentative identification of the C-X band of CS in the interstellar spectra of HD 24398 (zeta Per), HD 148184 (chi Oph), and HD 154368. The estimated column densities will be compared to the predictions of prevailing chemical models.

Smith, Andrew↗
NASA NTRS2018

The Origin of Titan's External Oxygen: Further Constraints from ALMA Upper Limits on CS and CH2NH

Titan's atmospheric inventory of oxygen compounds (H2O, CO2, CO) are thought to result from photochemistry acting on externally supplied oxygen species (O+, OH, H2O). These species potentially originate from two main sources: (1) cryogenic plumes from the active moon Enceladus and (2) micrometeoroid ablation. Enceladus is already suspected to be the major O+ source, which is required for CO creation. However, photochemical models also require H2O and OH influx to reproduce observed quantities of CO2 and H2O. Here, we exploit sulphur as a tracer to investigate the oxygen source because it has very different relative abundances in micrometeorites (S/O approx. 10(exp -2) and Enceladus' plumes (S/O approx. 10(exp -5). Photochemical models predict most sulphur is converted to CS in the upper atmosphere, so we use Atacama Large Millimeter/submillimeter Array (ALMA) observations at approx. 340 GHz to search for CS emission. We determined stringent CS 3 sigma stratospheric upper limits of 0.0074 ppb (uniform above 100 km) and 0.0256 ppb (uniform above 200 km). These upper limits are not quite stringent enough to distinguish between Enceladus and micrometeorite sources at the 3 sigma level and a contribution from micrometeorites cannot be ruled out, especially if external flux is toward the lower end of current estimates. Only the high flux micrometeorite source model of Hickson et al. can be rejected at 3 sigma. We determined a 3 sigma stratospheric upper limit for CH2NH of 0.35 ppb, which suggests cosmic rays may have a smaller influence in the lower stratosphere than predicted by some photochemical models. Disk-averaged C3H4 and C2H5CN profiles were determined and are consistent with previous ALMA and Cassini/CIRS measurements.

Teanby, N.A.↗
NASA NTRS2024

Accurate Infrared Line Lists for 20 Isotopologues of CS 2 at Room Temperature

To facilitate atmospheric and spectroscopic studies of carbon disulfide, or CS 2 , in both planetary and exoplanetary atmospheres, we adopt the “Best Theory + Reliable High-resolution Experiment” algorithm to generate semiempirical IR line lists for the 20 most abundant CS 2 isotopologues, denoted as Ames-296K. The IR lists are computed using the Ames-1 potential energy surface, refined using the experimental transition set and an ab initio dipole moment surface fitted from CCSD(T)/aug-cc-pV(T/Q/5+d)Z dipoles extrapolated to a one-particle basis set limit. The IR lists cover the range of 0–10,000 cm -1 , with an S 296K cutoff at 10 -31 cm -1 /molecule·cm -2 (abundance included). A “natural” IR line list at 296 K includes about 10 million lines of the 20 isotopologues, with their intensities scaled by the corresponding abundances. The zero-point energy, partition functions, and abundances are reported for each isotopologue. The energy levels in the global effective Hamiltonian model for 12 C 32 S 2 are adopted to improve the line position accuracy. This new IR list for the main isotopologue is denoted as A+I.296K. Reliable HITRAN2020 line positions are also utilized to improve the accuracy of the 32 S 12 C 34 S, 32 S 12 C 33 S, and 32 S 13 C 32 S isotopologue line lists. The final composite line list is validated against Pacific Northwest National Laboratory experimental cross sections, showing excellent agreement. The agreement supports the quality of the composite line list and the power of synergy between experiment and theory. The new data are proposed for use in updating and expanding the CS 2 data in HITRAN and other high-resolution IR databases. Supplementary files are available in Zenodo and AHED.

Exoplanet atmospheric composition↗
DOE OSTI2026

Online Alpha Monitoring of High Cs-137 Hanford and SRS High Level Waste with Tensioned Metastable Fluid Detectors

The Department of Energy’s Hanford and Savannah River Sites maintain millions of gallons of caustic supernate and salt high activity waste in their high-level waste (HLW) tank farm inventories. The Savannah River Site is currently treating this waste with a calixarene-based solvent extraction of Cs-137 to reduce these inventories. Hanford is employing an at-tank crystalline silico titanate (CST) based solid phase extraction methodology to reduce their liquid HLW inventories. Due to the high solubility of Cs-137 and the relative insolubility of the actinides in these caustic waste forms, the beta to alpha radioactivity ratio can often exceed six orders of magnitude in the feed solutions to these treatment processes. This unique characteristic leads to significant technical challenges in making rapid gross alpha measurements in the presence of the overwhelming beta, gamma, as well as dissolved sodium salt in these HLW matrices. Conventional radioanalytical techniques, such as liquid scintillation analysis or gas flow proportional counting require significant radiochemistry preparation prior to the radiometric measurements for gross alpha activity. These required pretreatments render these technologies untenable for rapid quantification of gross alpha activity that could be required to support on or at-line measurements ensuring a waste stream will meet regulatory requirements. The radiation measurement properties of Tensioned Metastable Fluid Detectors (TMFDs) have been studied by Purdue University’s Taleyarkhan research group for well over a decade. Fluids tensioned to the appropriate degree will rupture when struck by radiation, resulting in a measurable cavitation event. The negative pressure generating this tension can be adjusted by centrifugal rotation or by acoustic means in such a way that these cavitation events can be generated from alpha radiation but will not be generated by beta or gamma radiation. Purdue University and the Savannah River National Laboratory are currently collaborating to develop a gamma/beta blind, spectroscopic alpha measurement system based on the Tensioned Metastable Fluid Detector technology to provide a potential solution for performing rapid gross alpha measurements on these high gamma/beta sample matrices. Measurements using the Indirect Drive Acoustically Tensioned Metastable Fluid Detectors developed as part of this collaboration were performed with an alpha emitting radionuclide. Successful determination of gross alpha activity was observed, indicating a potential pathway for rapid gross alpha measurements in remote-handled shielded cells or in process situations requiring online alpha monitoring. Measurements using this system have been conducted on high beta activity solutions, demonstrating the beta blind capability of this system. Measurements are currently underway to test the system’s capability to measure gross alpha activity on Savannah River Site high level waste high Cs-137 samples that have been measured by the SRNL radiochemistry team. This work was supported by the DOE EM Technology Development program.

DiPrete, David [Savannah River National Laboratory↗
DOE OSTI2020

Materials Data on Cs(MnP)2 by Materials Project

Cs(MnP)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Cs1+ is bonded in a distorted body-centered cubic geometry to eight equivalent P+2.50- atoms. All Cs–P bond lengths are 3.66 Å. Mn2+ is bonded to four equivalent P+2.50- atoms to form a mixture of edge and corner-sharing MnP4 tetrahedra. All Mn–P bond lengths are 2.28 Å. P+2.50- is bonded in a 4-coordinate geometry to four equivalent Cs1+ and four equivalent Mn2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cs(SbSe2)2 by Materials Project

Cs(SbSe2)2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. Cs1+ is bonded in a 9-coordinate geometry to nine Se+1.75- atoms. There are a spread of Cs–Se bond distances ranging from 3.67–4.06 Å. There are two inequivalent Sb3+ sites. In the first Sb3+ site, Sb3+ is bonded to five Se+1.75- atoms to form distorted edge-sharing SbSe5 square pyramids. There are a spread of Sb–Se bond distances ranging from 2.59–3.34 Å. In the second Sb3+ site, Sb3+ is bonded in a see-saw-like geometry to four Se+1.75- atoms. There are a spread of Sb–Se bond distances ranging from 2.62–3.11 Å. There are four inequivalent Se+1.75- sites. In the first Se+1.75- site, Se+1.75- is bonded in a distorted rectangular see-saw-like geometry to one Cs1+ and three Sb3+ atoms. In the second Se+1.75- site, Se+1.75- is bonded in a 5-coordinate geometry to two equivalent Cs1+ and three Sb3+ atoms. In the third Se+1.75- site, Se+1.75- is bonded in a 1-coordinate geometry to three equivalent Cs1+, one Sb3+, and one Se+1.75- atom. The Se–Se bond length is 2.41 Å. In the fourth Se+1.75- site, Se+1.75- is bonded in a 2-coordinate geometry to three equivalent Cs1+ and two Sb3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cs(CoS)2 by Materials Project

Cs(CoS)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Cs1+ is bonded in a body-centered cubic geometry to eight equivalent S2- atoms. All Cs–S bond lengths are 3.55 Å. Co+1.50+ is bonded to four equivalent S2- atoms to form a mixture of corner and edge-sharing CoS4 tetrahedra. All Co–S bond lengths are 2.23 Å. S2- is bonded in a 4-coordinate geometry to four equivalent Cs1+ and four equivalent Co+1.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cs(WCl3)3 by Materials Project

Cs(WCl3)3 crystallizes in the trigonal P-3 space group. The structure is three-dimensional. Cs1+ is bonded in a 6-coordinate geometry to six equivalent Cl1- atoms. There are three shorter (3.65 Å) and three longer (3.68 Å) Cs–Cl bond lengths. W+2.67+ is bonded to five Cl1- atoms to form corner-sharing WCl5 square pyramids. There are a spread of W–Cl bond distances ranging from 2.41–2.49 Å. There are three inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a 3-coordinate geometry to two equivalent Cs1+ and one W+2.67+ atom. In the second Cl1- site, Cl1- is bonded in a 2-coordinate geometry to two equivalent W+2.67+ atoms. In the third Cl1- site, Cl1- is bonded in a 2-coordinate geometry to two equivalent W+2.67+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cs(AsRu)2 by Materials Project

Cs(RuAs)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Cs1+ is bonded in a body-centered cubic geometry to eight equivalent As3- atoms. All Cs–As bond lengths are 3.76 Å. Ru+2.50+ is bonded to four equivalent As3- atoms to form a mixture of corner and edge-sharing RuAs4 tetrahedra. All Ru–As bond lengths are 2.44 Å. As3- is bonded in a 8-coordinate geometry to four equivalent Cs1+ and four equivalent Ru+2.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cs(CoSe)2 by Materials Project

Cs(CoSe)2 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Cs1+ is bonded in a body-centered cubic geometry to eight equivalent Se2- atoms. All Cs–Se bond lengths are 3.64 Å. Co+1.50+ is bonded to four equivalent Se2- atoms to form a mixture of edge and corner-sharing CoSe4 tetrahedra. All Co–Se bond lengths are 2.36 Å. Se2- is bonded in a 8-coordinate geometry to four equivalent Cs1+ and four equivalent Co+1.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cs(SbS2)2 by Materials Project

Cs(SbS2)2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. Cs1+ is bonded in a 9-coordinate geometry to nine S+1.75- atoms. There are a spread of Cs–S bond distances ranging from 3.52–3.88 Å. There are two inequivalent Sb3+ sites. In the first Sb3+ site, Sb3+ is bonded in a rectangular see-saw-like geometry to four S+1.75- atoms. There are a spread of Sb–S bond distances ranging from 2.46–2.96 Å. In the second Sb3+ site, Sb3+ is bonded in a distorted rectangular see-saw-like geometry to four S+1.75- atoms. There are a spread of Sb–S bond distances ranging from 2.44–2.85 Å. There are four inequivalent S+1.75- sites. In the first S+1.75- site, S+1.75- is bonded in a 4-coordinate geometry to two equivalent Cs1+ and two Sb3+ atoms. In the second S+1.75- site, S+1.75- is bonded in a 2-coordinate geometry to three equivalent Cs1+ and two Sb3+ atoms. In the third S+1.75- site, S+1.75- is bonded in a 1-coordinate geometry to three equivalent Cs1+, one Sb3+, and one S+1.75- atom. The S–S bond length is 2.09 Å. In the fourth S+1.75- site, S+1.75- is bonded to one Cs1+ and three Sb3+ atoms to form distorted edge-sharing SCsSb3 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cs(NpSe3)2 by Materials Project

Cs(NpSe3)2 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Cs1+ is bonded to eight equivalent Se2- atoms to form face-sharing CsSe8 hexagonal bipyramids. All Cs–Se bond lengths are 3.77 Å. Np+5.50+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Np–Se bond distances ranging from 2.89–2.96 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to four equivalent Np+5.50+ atoms to form a mixture of distorted corner and edge-sharing SeNp4 trigonal pyramids. In the second Se2- site, Se2- is bonded in a 2-coordinate geometry to two equivalent Cs1+, two equivalent Np+5.50+, and two equivalent Se2- atoms. There are one shorter (2.68 Å) and one longer (2.81 Å) Se–Se bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cs(CoAs)2 by Materials Project

Cs(CoAs)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Cs1+ is bonded in a distorted body-centered cubic geometry to eight equivalent As3- atoms. All Cs–As bond lengths are 3.66 Å. Co+2.50+ is bonded to four equivalent As3- atoms to form a mixture of edge and corner-sharing CoAs4 tetrahedra. All Co–As bond lengths are 2.31 Å. As3- is bonded in a 8-coordinate geometry to four equivalent Cs1+ and four equivalent Co+2.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cs(PRu)2 by Materials Project

Cs(RuP)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Cs1+ is bonded in a body-centered cubic geometry to eight equivalent P3- atoms. All Cs–P bond lengths are 3.75 Å. Ru+2.50+ is bonded to four equivalent P3- atoms to form a mixture of edge and corner-sharing RuP4 tetrahedra. All Ru–P bond lengths are 2.32 Å. P3- is bonded in a 8-coordinate geometry to four equivalent Cs1+ and four equivalent Ru+2.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cs(ThTe3)2 by Materials Project

Cs(ThTe3)2 crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. Cs1+ is bonded to eight Te+1.50- atoms to form distorted face-sharing CsTe8 hexagonal bipyramids. There are four shorter (3.90 Å) and four longer (3.99 Å) Cs–Te bond lengths. There are two inequivalent Th4+ sites. In the first Th4+ site, Th4+ is bonded in a 8-coordinate geometry to eight Te+1.50- atoms. There are a spread of Th–Te bond distances ranging from 3.20–3.34 Å. In the second Th4+ site, Th4+ is bonded in a 8-coordinate geometry to eight Te+1.50- atoms. There are a spread of Th–Te bond distances ranging from 3.20–3.33 Å. There are four inequivalent Te+1.50- sites. In the first Te+1.50- site, Te+1.50- is bonded to four Th4+ atoms to form a mixture of distorted edge and corner-sharing TeTh4 trigonal pyramids. In the second Te+1.50- site, Te+1.50- is bonded to four Th4+ atoms to form a mixture of distorted edge and corner-sharing TeTh4 trigonal pyramids. In the third Te+1.50- site, Te+1.50- is bonded in a 2-coordinate geometry to two equivalent Cs1+, two equivalent Th4+, and two equivalent Te+1.50- atoms. There are one shorter (3.08 Å) and one longer (3.19 Å) Te–Te bond lengths. In the fourth Te+1.50- site, Te+1.50- is bonded in a 4-coordinate geometry to two equivalent Cs1+, two equivalent Th4+, and two equivalent Te+1.50- atoms. There are one shorter (3.04 Å) and one longer (3.23 Å) Te–Te bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cs(ThSe3)2 by Materials Project

Cs(ThSe3)2 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Cs1+ is bonded to eight equivalent Se+1.50- atoms to form face-sharing CsSe8 hexagonal bipyramids. All Cs–Se bond lengths are 3.79 Å. Th4+ is bonded in a 8-coordinate geometry to eight Se+1.50- atoms. There are a spread of Th–Se bond distances ranging from 2.99–3.03 Å. There are two inequivalent Se+1.50- sites. In the first Se+1.50- site, Se+1.50- is bonded in a 2-coordinate geometry to two equivalent Cs1+, two equivalent Th4+, and two equivalent Se+1.50- atoms. There are one shorter (2.76 Å) and one longer (2.82 Å) Se–Se bond lengths. In the second Se+1.50- site, Se+1.50- is bonded to four equivalent Th4+ atoms to form a mixture of distorted corner and edge-sharing SeTh4 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cs(FeP)2 by Materials Project

Cs(FeP)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Cs1+ is bonded in a distorted body-centered cubic geometry to eight equivalent P3- atoms. All Cs–P bond lengths are 3.70 Å. Fe+2.50+ is bonded to four equivalent P3- atoms to form a mixture of edge and corner-sharing FeP4 tetrahedra. All Fe–P bond lengths are 2.19 Å. P3- is bonded in a 4-coordinate geometry to four equivalent Cs1+ and four equivalent Fe+2.50+ atoms.

36 MATERIALS SCIENCE↗