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NASA NTRS1993

Possible near-IR channels for remote sensing precipitable water vapor from geostationary satellite platforms

Remote sensing of troposheric water vapor profiles from current geostationary weather satellites is made using a few broadband infrared (IR) channels in the 6-13 micron region. Uncertainties greater than 20% exist in derived water vapor values just above the surface from the IR emission measurements. In this paper, we propose three near-IR channels, one within the 0.94-micron water vapor band absorption region, and the other two in nearby atmospheric windows, for remote sensing of precipitable water vapor over land areas, excluding lakes and rivers, during daytime from future geostationary satellite platforms. The physical principles are as follows. The reflectance of most surface targets varies approximately linearly with wavelength near 1 micron. The solar radiation on the sun-surface-sensor ray path is attenuated by atmospheric water vapor. The ratio of the radiance from the absorption channel with the radiances from the two window channels removes the surface reflectance effects and yields approximately the mean atmospheric water vapor transmittance of the absorption channel. The integrated water vapor amount from ground to space can be obtained with a precision of better than 5% from the mean transmittance. Because surface reflectances vary slowly with time, temporal variation of precipitable water vapor can be determined reliably. High spatial resolution, precipitable water vapor images are derived from spectral data collected by the Airborne Visable-Infrared Imaging Spectrometer, which measures solar radiation reflected by the surface in the 0.4-2.5 micron region in 10-nm channels and has a ground instantaneous field of view of 20 m from its platform on an ER-2 aircraft at 20 km. The proposed near-IR reflectance technique would complement the IR emission techniques for remote sensing of water vapor profiles from geostationary satellite platforms, especially in the boundary layer where most of the water vapor is located.

Gao, B.-C.↗

NASA NTRS2001

Detection of Soluble and Fixed NH4+ in Clay Minerals by DTA and IR Reflectance Spectroscopy : A Potential Tool for Planetary Surface Exploration

Nitrogen is an essential element for life. It is the only element among the six major biogenic elements, C, O, S, O, P, H, whose presence in the Martian soil has not been positively and directly established. We describe here a study assessing the ability to detect NH4 in soils by two methods: differential thermal analysis (DTA) and infrared (IR) reflectance spectroscopy. Four standard clay minerals (kaolinite, montmorillonite, illite and attapulgite) and an altered tephra sample from Mauna Kea were treated with NH4 in this study. Samples of the NH4-treated and leached clays were analyzed by DTA and infrared (IR) reflectance spectroscopy to quantify the delectability of soluble and sorbed/fixed NH4. An exotherm at 270-280 C was clearly detected in the DTA curves of NH4-treated (non-leached) samples. This feature is assigned to the thermal decomposition reaction of NH4. Spectral bands observed at 1.56, 2.05, 2.12, 3.06, 3.3, 3.5, 5.7 and 7.0 microns in the reflectance spectra of NH4-treated and leached samples are assigned to the sorbed/fixed ammonium in the clays. The montmorillonite has shown the most intense absorbance due to fixed ammonium among the leached samples in this study, as a result of its high cation sorption capacity. It is concluded that the presence of sorbed or fixed NH4 in clays may be detected by infrared (IR) reflectance or emission spectroscopy. Distinction between soluble and sorbed NH4 may be achieved through the presence or absence of several spectral features assigned to the sorbed NH4 moietyi and, specifically, by use of the 4.2 micrometer feature assigned to solution NH4. Thermal analyses furnish supporting evidence of ammonia in our study through detection of N released at temperatures of 270-330 C. Based on these results it is estimated that IR spectra measured from a rover should be able to detect ammonia if present above 20 mg NH4/g sample in the surface layers. Orbital IR spectra and thermal analyses measured on a rover may be able to detect ammonia in soils as well but at higher abundances. The spectral features at 3.06 and 7.0 microns due to bound NH4 in clays and altered Hawaiian tephra appear to be the most promising for detection by orbital spectrometers. If N species are present on Mars the sedimentary deposits may be the best regions to look for them.

Janice, Bishop↗

NASA NTRS1997

Mid-IR Spectra Herbig Ae/Be Stars

Herbig Ae/Be stars are intermediate mass pre-main sequence stars, the higher mass analogues to the T Tauri stars. Because of their higher mass, they are expected form more rapidly than the T Tauri stars. Whether the Herbig Ae/Be stars accrete only from collapsing infalling envelopes or whether accrete through geometrically flattened viscous accretion disks is of current debate. When the Herbig Ae/Be stars reach the main sequence they form a class called Vega-like stars which are known from their IR excesses to have debris disks, such as the famous beta Pictoris. The evolutionary scenario between the pre-main sequence Herbig Ae/Be stars and the main sequence Vega-like stars is not yet revealed and it bears on the possibility of the presence of Habitable Zone planets around the A stars. Photometric studies of Herbig Ae/Be stars have revealed that most are variable in the optical, and a subset of stars show non-periodic drops of about 2 magnitudes. These drops in visible light are accompanied by changes in their colors: at first the starlight becomes reddened, and then it becomes bluer, the polarization goes from less than 0.1 % to roughly 1% during these minima. The theory postulated by V. Grinnin is that large cometary bodies on highly eccentric orbits occult the star on their way to being sublimed, for systems that are viewed edge-on. This theory is one of several controversial theories about the nature of Herbig Ae/Be stars. A 5 year mid-IR spectrophotometric monitoring campaign was begun by Wooden and Butner in 1992 to look for correlations between the variations in visible photometry and mid-IR dust emission features. Generally the approximately 20 stars that have been observed by the NASA Ames HIFOGS spectrometer have been steady at 10 microns. There are a handful, however, that have shown variable mid-IR spectra, with 2 showing variations in both the continuum and features anti-correlated with visual photometry, and 3 showing variations in the emission features only while the continuum level remained unchanged. The first 2 stars mentioned probably have reprocessing envelopes. The other 3 stars gives important clues to the controversy over the geometry of the gas and dust around these pre-main sequence stars: the steady underlying 10 microns continuum and variable features indicates that an optically thick continuum probably arising from an accretion disk is decoupled from the optically thin emission features which may arise in a disk atmosphere. Bernadette Rodgers has joined this monitoring campaign in the near-IR using GRIMII with the goal of detecting variations in the hot dust continuum and the gas density in the dense accretion region close to these stars.

Wooden, Diane↗

NASA NTRS2003

NASA's Far-IR/Submillimeter Roadmap Missions SAFIR and SPECS

The far-IR is rich with information about star, disk and planet formation because protostars emit predominantly in this spectral range, and the radiation can escape from the inherently dusty stellar birth sites. Spectral lines contain particularly valuable information about the cooling, collapse, and chemistry of molecular cloud cores and protostars. However, the interpretation of line intensities and profiles is model-dependent; ultimately, high angular resolution is needed to break model degeneracy and definitively characterize the source. Processes occurring on scales smaller than 10,000 AU (72 arcsec at 140 pc, where the nearest protostellar objects are found) likely affect the stellar initial mass function and determine the product of cloud collapse (Binary star or planetary system? How many planets, and what kind will they be?) The next-generation far-IR observatories SIRTF, SOFIA, and Herschel will revolutionize star formation studies and leave the community yearning for telescopes that operate in this spectral region but provide many orders of magnitude better angular resolution. NASA's space science roadmap includes the JWST-scale Single Aperture Far-IR (SAFIR) telescope and the 1 km maximum baseline far-IR interferometer, SPECS (the Submillimeter Probe of the Evolution of Cosmic Structure). I will give the scientific motivation for these missions, describe mission concepts and telescope measurement capabilities, and compare these capabilities with those of the next-generation IR telescopes and with the complementary JWST and ALMA. I will also describe the Space Infrared Interferometric Telescope (SPIRIT), a science and technology pathfinder for SPECS, which could be ready to launch in about a decade. At 100 microns, SAFIR will provide 2.5 arcsec resolution (10 times better than SIRTF), SPIRIT will provide 0.25 arcsec resolution, and SPECS will provide 10 milli-arcsec resolution, which is comparable to that of the Hubble Space Telescope.

Leisawitz, David↗

NASA NTRS2004

Atmospheric Trace Gas Abundances and Stable Isotope Ratios via IR-LIF

We propose to develop new technologies with support provided by PIDDP that will enable the in situ measurements of abundances and stable isotope ratios in important radiatively and biogenically active gases such as carbon dioxide, carbon monoxide, water, methane, nitrous oxide, and hydrogen sulfide to very high precision (0.1 per mil or better for the isotopic ratios, for example). Such measurements, impossible at present, could provide pivotal new constraints on the global (bio)geochemical budgets of these critical species, and could also be used to examine the dynamics of atmospheric transport on Mars, Titan, and other solar system bodies. We believe the combination of solid state light sources with imaging of the IR laser induced fluorescence (IR-LIF) via newly available detector arrays will make such in situ measurements possible for the first time. Even under ambient terrestrial conditions, the LIF yield from vibrational excitation of species such as water and carbon dioxide should produce emission measures well in excess of ten billion photons/sec from samples volumes of order 1 c.c. These count rates can, in principle, yield detection limits into the sub-ppt range that are required for the in situ isotopic study of atmospheric trace gases. While promising, such technologies are relatively immature, but developing rapidly, and there are a great many uncertainties regarding their applicability to in situ IR-LIF planetary studies. We therefore feel PIDDP support will be critical to developing these new tools, and propose a three-year program to combine microchip near-IR lasers with low background detection axes and state-of-the-art HgCdTe detectors developed for astronomical spectroscopy to investigate the sensitivity of IR-LIF under realistic planetary conditions, to optimize the optical pumping and filtering schemes for important species, and to apply the spectrometer to the non-destructive measurement of stable isotopes in a variety of test samples. These studies form the necessary precursors to the development of compact, lightweight stable isotope/trace gas sensors for future planetary missions.

Blake, Geoffrey A.↗

NASA NTRS2013

Cross-correlating Cosmic IR and X-ray Background Fluctuations: Evidence of Significant Black Hole Populations Among the CIB Sources

In order to understand the nature of the sources producing the recently uncovered cosmic infrared background (CIB) fluctuations, we study cross-correlations between the fluctuations in the source-subtracted CIB from Spitzer/IRAC data and the unresolved cosmic X-ray background from deep Chandra observations. Our study uses data from the EGS/AEGIS field, where both data sets cover an approx = 8' x 45' region of the sky. Our measurement is the cross-power spectrum between the IR and X-ray data. The cross-power signal between the IRAC maps at 3.6 micron and 4.5 micron and the Chandra [0.5-2] keV data has been detected, at angular scales approx >20'', with an overall significance of approx = 3.8 sigma and approx. = 5.6 sigma, respectively. At the same time we find no evidence of significant cross-correlations at the harder Chandra bands. The cross-correlation signal is produced by individual IR sources with 3.6 micron and 4.5 micron magnitudes m(sub AB) approx. > 25-26 and [0.5-2] keV X-ray fluxes << 7 × 10(exp -177 erg sq. cm/ s. We determine that at least 15%-25% of the large scale power of the CIB fluctuations is correlated with the spatial power spectrum of the X-ray fluctuations. If this correlation is attributed to emission from accretion processes at both IR and X-ray wavelengths, this implies a much higher fraction of accreting black holes than among the known populations. We discuss the various possible origins for the cross-power signal and show that neither local foregrounds nor the known remaining normal galaxies and active galactic nuclei can reproduce the measurements. These observational results are an important new constraint on theoretical modeling of the near-IR CIB fluctuations. local foregrounds, nor the known remaining normal galaxies and active galactic nuclei (AGN) can reproduce the measurements. These observational results are an important new constraint on theoretical modeling of the near-IR CIB fluctuations

Cosmic X-ray Background (CXB)↗

DOE OSTI2020

Materials Data on Ir(SeBr3)3 by Materials Project

Ir(SeBr2)3(Br)3 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of twelve hydrobromic acid molecules and four Ir(SeBr2)3 clusters. In each Ir(SeBr2)3 cluster, Ir3+ is bonded in a distorted T-shaped geometry to three Se2- atoms. There are one shorter (2.41 Å) and two longer (2.42 Å) Ir–Se bond lengths. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a distorted trigonal non-coplanar geometry to one Ir3+ and two Br+0.33+ atoms. There are one shorter (2.38 Å) and one longer (2.40 Å) Se–Br bond lengths. In the second Se2- site, Se2- is bonded in a distorted trigonal non-coplanar geometry to one Ir3+ and two Br+0.33+ atoms. There are one shorter (2.37 Å) and one longer (2.41 Å) Se–Br bond lengths. In the third Se2- site, Se2- is bonded in a distorted trigonal non-coplanar geometry to one Ir3+ and two Br+0.33+ atoms. There are one shorter (2.39 Å) and one longer (2.41 Å) Se–Br bond lengths. There are six inequivalent Br+0.33+ sites. In the first Br+0.33+ site, Br+0.33+ is bonded in a single-bond geometry to one Se2- atom. In the second Br+0.33+ site, Br+0.33+ is bonded in a single-bond geometry to one Se2- atom. In the third Br+0.33+ site, Br+0.33+ is bonded in a single-bond geometry to one Se2- atom. In the fourth Br+0.33+ site, Br+0.33+ is bonded in a single-bond geometry to one Se2- atom. In the fifth Br+0.33+ site, Br+0.33+ is bonded in a single-bond geometry to one Se2- atom. In the sixth Br+0.33+ site, Br+0.33+ is bonded in a single-bond geometry to one Se2- atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Ir(N3O4)3 by Materials Project

(Ir(NO2)6)2(N2)3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is zero-dimensional and consists of twelve ammonia molecules and four Ir(NO2)6 clusters. In each Ir(NO2)6 cluster, Ir3+ is bonded in a cuboctahedral geometry to twelve equivalent O2- atoms. All Ir–O bond lengths are 2.26 Å. N+2.33+ is bonded in a 4-coordinate geometry to four equivalent O2- atoms. All N–O bond lengths are 1.95 Å. O2- is bonded in a 3-coordinate geometry to one Ir3+ and two equivalent N+2.33+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Ir(NCl)4 by Materials Project

Ir(NCl)4 crystallizes in the triclinic P1 space group. The structure is zero-dimensional and consists of one Ir(NCl)4 cluster. Ir4+ is bonded in a distorted trigonal bipyramidal geometry to three N and two Cl1- atoms. There are a spread of Ir–N bond distances ranging from 1.73–2.01 Å. There are one shorter (2.33 Å) and one longer (2.47 Å) Ir–Cl bond lengths. There are four inequivalent N sites. In the first N site, N is bonded in a distorted bent 120 degrees geometry to one Ir4+ and one Cl1- atom. The N–Cl bond length is 1.57 Å. In the second N site, N is bonded in a water-like geometry to two Cl1- atoms. There is one shorter (1.60 Å) and one longer (2.05 Å) N–Cl bond length. In the third N site, N is bonded in a single-bond geometry to one Ir4+ atom. In the fourth N site, N is bonded in a single-bond geometry to one Ir4+ atom. There are four inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a single-bond geometry to one Ir4+ atom. In the second Cl1- site, Cl1- is bonded in a distorted single-bond geometry to one Ir4+ atom. In the third Cl1- site, Cl1- is bonded in a single-bond geometry to one N atom. In the fourth Cl1- site, Cl1- is bonded in a water-like geometry to two N atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Carbon monoxide chemistry of α-V70I Mo-nitrogenase: Evidence from EPR- and IR-monitored photolysis – or, what a difference a methyl makes

A critical step in the global nitrogen cycle is the conversion of dinitrogen into biologically accessible ammonia. In Nature this is accomplished by the nitrogenase (N 2 ase) family of enzymes. Carbon monoxide (CO) has long been known as an inhibitor of dinitrogen reduction by N 2 ase, but it can also be a substrate of the enzyme, when it is catalytically reduced to hydrocarbons. Understanding the CO interactions with N 2 ases are thus relevant to both dinitrogen fixation and Fischer-Tropsch-like chemistry. Here, in this work, the interaction of CO with the α-V70I variant of Azotobacter vinelandii MoFe N 2 ase was investigated using electron paramagnetic resonance (EPR) and infrared (IR) monitored photolysis of bound CO under cryogenic conditions. This was supplemented by further analysis of stopped-flow Fourier transform IR (SF-FT-IR) data under turnover conditions. The α-V70I variant adds a single methyl group close to the FeMo-cofactor active site, and the results show that this inhibits and slows, but does not substantially chemically change, the binding of CO to the FeMocofactor. The EPR spectra of both the hi-CO and lo-CO states closely resemble those from the wild-type enzyme. Similarly, the SF-FT-IR spectra of CO inhibited α-V70I and wild-type enzyme are strikingly similar, showing only small shifts in band energies which allow better interpretation of the published wild-type spectra. The extra carbon does, however, impact and inhibit the photochemical release and migration of CO at cryogenic temperatures, resulting in novel CO-bound species. These include a product species, termed Lo-1*, which may involve CO photochemically migrating on the FeMo-cofactor.

Carbon monoxide↗

DOE OSTI2017

Mock Target Window OTR and IR Design and Testing

In order to fully verify temperature measurements made on the target window using infrared (IR) optical non-contact methods, actual comparative measurements are made with a real beam distribution as the heat source using Argonne National Laboratory’s (ANL) 35 MeV electron accelerator. Using Monte Carlo N-Particle (MCNP) simulations and thermal Finite Element Analysis (FEA), a cooled mock target window with thermocouple implants is designed to be used in such a test to achieve window temperatures up to 700°C. An uncoated and blackcoated mock window is designed to enhance the IR temperature measurements and verify optical transmitted radiation (OTR) imagery. This allows us to fully verify and characterize our temperature accuracy with our current IR camera method and any future method we may wish to explore using actual production conditions. This test also provides us with valuable conclusions/concerns regarding the calibration method we developed using our IR test stand at TA-53 in MPF-14.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

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↗

DOE OSTI2024

NO Reduction with CO on Low‐loaded Platinum‐group Metals (Rh, Ru, Pd, Pt, and Ir) Atomically Dispersed on Ceria

Abstract Low‐loaded platinum‐group single‐atom catalysts on CeO 2 (M 1 /CeO 2 ) were synthesized via high‐temperature atom trapping (AT) and tested for the NO+CO reaction under dry and wet conditions. The activity of these catalysts for NO+CO reaction follows the order Rh>Pd≈Ru>Pt>Ir. For Rh, Ru, and Pd single‐atom catalysts, the N 2 O byproduct is formed but not clearly observed in Ir and Pt cases, which may result from the higher reaction temperature (>200 °C) required for Pt and Ir catalysts. The presence of water can promote the activity of these M 1 /CeO 2 catalysts for the NO+CO reaction. Under wet conditions, significant NH 3 formation occurred during the reaction, which is due to the co‐existence of water‐gas‐shift reaction on these catalysts. Compared with Pt, Pd and Ir, the Rh and Ru single‐atom catalysts show higher selectivity to NH 3 species, resulting from the hydride species on the surface. Among all tested catalysts, Ru 1 /CeO 2 shows the highest production of ammonia and highest CO conversion due to excellent water‐gas‐shift activity, whereas Pd 1 /CeO 2 shows lowest ammonia production. Rh 1 /CeO 2 shows the best low temperature NO reduction activity among all tested catalysts.

Tian, Jinshu↗

DOE OSTI2016

Open EFTs, IR effects & late-time resummations: systematic corrections in stochastic inflation

Though simple inflationary models describe the CMB well, their corrections are often plagued by infrared effects that obstruct a reliable calculation of late-time behaviour. Here we adapt to cosmology tools designed to address similar issues in other physical systems with the goal of making reliable late-time inflationary predictions. The main such tool is Open EFTs which reduce in the inflationary case to Stochastic Inflation plus calculable corrections. We apply this to a simple inflationary model that is complicated enough to have dangerous IR behaviour yet simple enough to allow the inference of late-time behaviour. We find corrections to standard Stochastic Inflationary predictions for the noise and drift, and we find these corrections ensure the IR finiteness of both these quantities. The late-time probability distribution, P(Φ), for super-Hubble field fluctuations are obtained as functions of the noise and drift and so these too are IR finite. We compare our results to other methods (such as large-N models) and find they agree when these models are reliable. In all cases we can explore in detail we find IR secular effects describe the slow accumulation of small perturbations to give a big effect: a significant distortion of the late-time probability distribution for the field. But the energy density associated with this is only of order H 4 at late times and so does not generate a dramatic gravitational back-reaction.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2017

IR-study of hydrated surface of oxide photocatalysts

IR spectroscopy combined with thermogravimetry was used to investigate the effect of the pretreatment temperature on the degree of coverage of the surface of oxide photocatalysts, TiO{sub 2}, ZnO, CeO{sub 2}, and Zn{sup 2+}/TiO{sub 2}, with water. At room temperature, the amount of adsorbed water per unit area of photocatalysts in the air decreases in the row: ZnO ≥ CeO{sub 2} > TiO{sub 2}, whereas the temperature needed for complete removal of physically adsorbed water from the studied oxides decreases in the reverse order. Water is removed from the ZnO surface by evacuation at room temperature; in the case of CeO{sub 2} and TiO{sub 2}, it desorbs at 200 and 300 °С, respectively. The terminal OH groups on the oxide surface are the most strongly bonded with adsorbed water. In the zinc modified TiO{sub 2}, the terminal OH groups are firstly replaced by Zn cations, which causes both hydrophobization of the samples under atmospheric conditions and a decrease in the temperature at which physically adsorbed water is released from the surface. Evacuation of ZnO at 350 °C removes the surface oxygen and results in the generation of the surface defect sites. This causes strong absorption in the IR spectra in the region of 1000—4000 cm{sup –1}. The formation of surface defects probably causes the appearance of donor levels in the band gap. The energy of the transition of electrons from these levels to the conduction band corresponds to the energy of the IR radiation. After oxidation of such samples in O{sub 2} at 350 °C, strong absorption in the IR spectra disappears.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Structure sensitivity of n -butane hydrogenolysis on supported Ir catalysts

Hydrogenolysis of alkanes has been widely reported as structure sensitive reaction on transition metal heterogeneous catalysts with metal particle sizes ranging between 1 and 20 nm. In this work, a series of Ir/MgAl 2 O 4 and Ir/SiO 2 catalysts with different Ir particle sizes ranging from subnanometer clusters (<1 nm) to nanoparticles (1–3 nm) were prepared and tested for n-butane hydrogenolysis. Our results show that the activity towards n-butane hydrogenolysis increases as Ir particle size increases in the lower particle size range, goes through a maximum at ~1.4–1.6 nm and then drops with a further increase in particle size. In this work, the product distribution at low temperature (170–190 °C) is dominated by central and terminal CAC bond cleavage of n-butane, and less by two CAC bond cleavage or further hydrogenolysis of the propane and ethane products. The selectivity to central CAC bond cleavage is highly dependent on the size of Ir and increases with a decrease in particle size down to ~1.4 nm but remains constant with further decrease in size. The results show that an Ir size of ~1.4 nm is optimum for n-butane hydrogenolysis activity and selectivity towards ethane.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2013

Two Keggin-type heteropolytungstates with transition metal as a central atom: Crystal structure and magnetic study with 2D-IR correlation spectroscopy

Two Keggin-type heteropolytungstates, [Co(phen)₃]₃[CoW₁₂O₄₀]·9H₂O 1 (phen=1,10-phenanthroline) and [Fe(phen)₃]₂[FeW₁₂O₄₀]·H₃O·H₂O 2, have been synthesized via the hydrothermal technique and characterized by single crystal X-ray diffraction analyses, IR, XPS, TG analysis, UV–DRS, XRD, thermal-dependent and magnetic-dependent 2D-COS IR (two-dimensional infrared correlation spectroscopy). Crystal structure analysis reveals that the polyanions in compound 1 are linked into 3D supramolecule through hydrogen bonding interactions between lattice water molecules and terminal oxygen atoms of polyanion units, and [Co(phen)₃]²⁺ cations distributed in the polyanion framework with many hydrogen bonding interactions. The XPS spectra indicate that all the Co atoms in 1 are +2 oxidation state, the Fe atoms in 2 existing with +2 and +3 mixed oxidation states. - Graphical abstract: The magnetic-dependent synchronous 2D correlation IR spectra of 1 (a), 2 (b) over 0–50 mT in the range of 600–1000 cm⁻¹, the obvious response indicate two Keggin polyanions skeleton susceptible to applied magnetic field. Highlights: • Two Keggin-type heteropolytungstates with transition metal as a central atom has been obtained. • Compound 1 forms into 3D supramolecular architecture through hydrogen bonding between water molecules and polyanions. • Magnetic-dependent 2D-IR correlation spectroscopy was introduced to discuss the magnetism of polyoxometalate.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2018

PbGa6Te10 crystals for IR laser operated piezoelectricity

Highlights: • High-quality single crystals PbGa{sub 6}Te{sub 10} grown by Bridgman method. • PbGa{sub 6}Te{sub 10} crystals were characterized by X-ray photoelectron spectroscopy. • Temperature dependent thermal conductivity was investigated . • Was discovered a rare possibility to improve piezoelectric features using the external infrared laser beams. • The observed effect opens a new stage for the production of the IR operated devices including piezotronics. - Abstract: A ternary compound PbGa{sub 6}Te{sub 10} grown by Bridgman method was studied with respect to IR induced piezoelectricity. We have found an opportunity to induce piezoelectric features using the external infrared laser (IR) beams for PbGa{sub 6}Te{sub 10} crystals. The three principal wavelengths corresponding to fundamental 10.6 μm, doubled frequency 5.3 μm and third harmonic 3.5 μm laser beams were explored as photoinduced beams. Maximally achieved IR induced piezoelectricity was observed at laser induced wavelength 5.3 μm. The optimal photoinduced power density was varied within 150–160 MW/cm{sup 2} . The observed space gratings are very crucial for the observed photo-induced piezoelectricity, which is indicated, that we deal with interference of the photoinduced coherent beams. The role of the surface states was discussed based on the XPS spectra. Additionally, the temperature dependence of thermal diffusivity was measured. The determined thermal conductivity indicates prevailingly the phonon contribution and possesses very low values in the measured temperature ranges.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗