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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

AmeriFlux FLUXNET-1F US-CF2 CAF-LTAR Cook West

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site US-CF2 CAF-LTAR Cook West. This is the FLUXNET version of the carbon flux data for the site US-CF2 CAF-LTAR Cook West produced by applying the standard ONEFlux (1F) software. Site Description - CF2 has operated since May 2017 at the R.J. Cook Agronomy Farm outside of Pullman, Washington, and monitors the conventionally tilled side of a paired-catchment study that is part of the Longterm Agroecosystem Research (LTAR) site common experiment. CF2 is located in “Cook West,” a field that has been in conventional tillage since prior to 1998 and constitutes the Prevalent treatment of the common experiment. In this case, conventional tillage involves chisel plowing after the winter wheat phase of rotations (approximately every 3-4 years) and occasional harrowing. CF2 is paired with the CF1 tower location in “Cook East,” which has been in no-till since 1998 and represents the Alternative treatment of the common experiment. Both fields are planted in the same crops every year. Cook Agronomy Farm is in the high precipitation agroecological zone of the Columbia Plateau’s dryland cropping region. Crop rotations are wheat-based and include winter wheat, spring wheat, chickpea, spring canola, and winter peas. Wheat is the principal cash crop, with other crops grown in rotation for diversity, nutrient, and pest management. Soils are predominantly silt loam texture Mollisols in the Palouse, Thatuna, Naff soil series. The CF2 tower replaced US-RC2, which operated 2012-2016 in a neighboring field that was also conventionally tilled. CF2 and RC2 have distinct footprints, aspects, and soil series compositions.

Huggins, Dave↗
NASA NTRS1999

CF2 Detection in Radio-Frequency Ar/CHF3 Plasmas by Fourier Transform Infrared Spectroscopy

CFx radicals, in particular CF2, are instrumental in anisotropic etching of SiO2. In order to optimize the CFx radical population in a given process environment, it is imperative that we understand their production mechanism. Towards this goal, we have conducted a series of quantitative measurements of CF2 radicals in low pressure RF plasmas similar to those used in SiO2 etching. In this study, we present preliminary results for Ar/CHF3 plasmas operating at pressures ranging from 10-50 mTorr and powers ranging from 100-500 W in the GEC reference cell, modified for inductive (transformer) coupling. Fourier transform infrared (FTIR) spectroscop) is used to observe the absorption features of the CF2 radical in the 1114 cm-1 and 1096 cm-1 spectral regions. The FTIR spectrometer is equipped with a high-sensitivity mercury cadmium telluride (MCT) detector and has afixed resolution of 0.125 cm- 1. The CF2 concentrations are measured for a range of operating pressures and discharge power levels, and are compared to measurements of the relative CF2 concentrations made by mass spectrometry using the method of appearance potential for radical selectivity.

Kim, J. S.↗
NASA NTRS2004

A Monte Carlo Sensitivity Analysis of CF2 and CF Radical Densities in a c-C4F8 Plasma

A Monte Carlo sensitivity analysis is used to build a plasma chemistry model for octacyclofluorobutane (c-C4F8) which is commonly used in dielectric etch. Experimental data are used both quantitatively and quantitatively to analyze the gas phase and gas surface reactions for neutral radical chemistry. The sensitivity data of the resulting model identifies a few critical gas phase and surface aided reactions that account for most of the uncertainty in the CF2 and CF radical densities. Electron impact dissociation of small radicals (CF2 and CF) and their surface recombination reactions are found to be the rate-limiting steps in the neutral radical chemistry. The relative rates for these electron impact dissociation and surface recombination reactions are also suggested. The resulting mechanism is able to explain the measurements of CF2 and CF densities available in the literature and also their hollow spatial density profiles.

Bose, Deepak↗
DOE OSTI2026

AmeriFlux FLUXNET-1F CA-CF2 Churchill Fen Site 2

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site CA-CF2 Churchill Fen Site 2. This is the FLUXNET version of the carbon flux data for the site CA-CF2 Churchill Fen Site 2 produced by applying the standard ONEFlux (1F) software. Site Description - Fen site dominated by sedges. Flat, high water table. Frozen for long periods each year. Close to Arctic Ocean coast so affected by land/sea breezes and coastal weather.

Tenuta, Mario [University of Manitoba]↗
DOE OSTI2020

Materials Data on CF2 by Materials Project

CF2 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two difluoromethane molecules, two fluoroform molecules, and two fluoromethane molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2020

AmeriFlux CA-CF2 Churchill Fen Site 2

This is the AmeriFlux version of the carbon flux data for the site CA-CF2 Churchill Fen Site 2. Site Description - Fen site dominated by sedges. Flat, high water table. Frozen for long periods each year. Close to Arctic Ocean coast so affected by land/sea breezes and coastal weather.

Tenuta, Mario↗
NASA NTRS1986

CF2 and CFCl fluorescence from VUV excitation of C2F3Cl

The photoexcitation process of C2F3Cl molecule was investigated in the 106 to 230 nm region using synchrotron radiation as a light source. Photoabsorption and fluorescence cross sections were measured and used to determine the fluorescence quantum yield. Fluorescence yield starts to appear at 170 nm and increases to about 2% at 155 nm. The fluorescence spectra were dispersed to identify the emitting species. At the excitation wavelength of 155 nm, the emission system is CFCl (Hermitian conjugate of A - Hermitian conjugate of X), and at 123.9 nm, both the CF2 (Hermitian conjugate of A - Hermitian conjugate of X) and CFCl (Hermitian conjugate of A - Hermitian conjugate of X) systems are observed. The dissociation processes that produced these excited species are discussed.

Nee, J. B.↗
NASA NTRS1987

CF2 and CFCl fluorescence from VUV excitation of C2F3Cl

The photoexcitation process of the C2F3Cl molecule was investigated in the 106-230-nm region using synchrotron radiation as a light source. Photoabsorption and fluorescence cross sections were measured and used to determine the fluorescence quantum yield. Fluorescence yield starts to appear at 170 nm and increases to about 2 percent at 155 nm. The fluorescence spectra were dispersed to identify the emitting species. The (A-X) systems of CFCl (at excitation wavelengths 155 and 123.9 nm) and CF2 (at 123.9 nm) are observed. The dissociation processes that produced these excited species are discussed.

Nee, J. B.↗
DOE OSTI2020

Materials Data on Sb2H10(CF2)3 by Materials Project

C3SbH10SbF6 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of eight C3SbH10 clusters and eight SbF6 clusters. In four of the C3SbH10 clusters, there are three inequivalent C+1.33- sites. In the first C+1.33- site, C+1.33- is bonded in a distorted trigonal non-coplanar geometry to one Sb and three H1+ atoms. The C–Sb bond length is 2.12 Å. There is two shorter (1.09 Å) and one longer (1.10 Å) C–H bond length. In the second C+1.33- site, C+1.33- is bonded in a distorted trigonal non-coplanar geometry to one Sb and three H1+ atoms. The C–Sb bond length is 2.12 Å. There is two shorter (1.09 Å) and one longer (1.10 Å) C–H bond length. In the third C+1.33- site, C+1.33- is bonded in a distorted trigonal non-coplanar geometry to one Sb and three H1+ atoms. The C–Sb bond length is 2.12 Å. There is two shorter (1.09 Å) and one longer (1.10 Å) C–H bond length. Sb is bonded in a tetrahedral geometry to three C+1.33- and one H1+ atom. The Sb–H bond length is 1.69 Å. There are ten inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C+1.33- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C+1.33- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C+1.33- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one C+1.33- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one Sb atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one C+1.33- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one C+1.33- atom. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one C+1.33- atom. In the ninth H1+ site, H1+ is bonded in a single-bond geometry to one C+1.33- atom. In the tenth H1+ site, H1+ is bonded in a single-bond geometry to one C+1.33- atom. In four of the C3SbH10 clusters, there are three inequivalent C+1.33- sites. In the first C+1.33- site, C+1.33- is bonded in a distorted trigonal non-coplanar geometry to one Sb and three H1+ atoms. The C–Sb bond length is 2.12 Å. There is two shorter (1.09 Å) and one longer (1.10 Å) C–H bond length. In the second C+1.33- site, C+1.33- is bonded in a distorted trigonal non-coplanar geometry to one Sb and three H1+ atoms. The C–Sb bond length is 2.12 Å. There is two shorter (1.09 Å) and one longer (1.10 Å) C–H bond length. In the third C+1.33- site, C+1.33- is bonded in a distorted trigonal non-coplanar geometry to one Sb and three H1+ atoms. The C–Sb bond length is 2.12 Å. There is two shorter (1.09 Å) and one longer (1.10 Å) C–H bond length. Sb is bonded in a tetrahedral geometry to three C+1.33- and one H1+ atom. The Sb–H bond length is 1.69 Å. There are ten inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C+1.33- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C+1.33- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C+1.33- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one C+1.33- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one C+1.33- atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one C+1.33- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one Sb atom. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one C+1.33- atom. In the ninth H1+ site, H1+ is bonded in a single-bond geometry to one C+1.33- atom. In the tenth H1+ site, H1+ is bonded in a single-bond geometry to one C+1.33- atom. In each SbF6 cluster, Sb is bonded in an octahedral geometry to six F1- atoms. There are a spread of Sb–F bond distances ranging from 1.91–1.94 Å. There are six inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one Sb atom. In the second F1- site, F1- is bonded in a single-bond geometry to one Sb atom. In the third F1- site, F1- is bonded in a single-bond geometry to one Sb atom. In the fourth F1- site, F1- is bonded in a single-bond geometry to one Sb atom. In the fifth F1- site, F1- is bonded in a single-bond geometry to one Sb atom. In the sixth F1- site, F1- is bonded in a single-bond geometry to one Sb atom.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Quantitative evaluation of perfluorinated alkanethiol molecular order on gold surfaces

Self-assembled monolayers (SAMs) of perfluoroalkanethiols [CF3(CF2)xCH2CH2SH (x = 3, 5, 7, and 9)] on gold were characterized by x-ray photoelectron spectroscopy (XPS), near edge x-ray absorption fine structure (NEXAFS), and static time-of-flight secondary ion mass spectrometry (ToF-SIMS). Perfluoroalkanethiols of several chain lengths were synthesized using a known hydride reduction method for transforming commercially available perfluoroalkyliodides to corresponding perfluoroalkanethiols. This strategy provides improved product yields compared to other known routes based on hydrolysis from the common thioacetyl perfluoroalkyl intermediate. Angle-dependent XPS analysis revealed that CF3(CF2)xCH2CH2SH (x = 5, 7, and 9; F6, F8, and F10, respectively) SAMs on gold exhibited significant enrichment of the terminal CF3 group at the outer monolayer surface with the sulfur present as a metal-bound thiolate located at the monolayer-gold interface. XPS of the CF3(CF2)3CH2CH2SH (F4) monolayer revealed a thin film with a significant (>50%) amount of hydrocarbon contamination consistent with poorly organized monolayers, while the longest thiol (F10) showed XPS signals attributed to substantial ordering and anisotropy. ToF-SIMS spectra from all four SAMs contained molecular ions representative of the particular perfluorinated thiol used to prepare the monolayer. NEXAFS methods were used to determine degrees of ordering and average tilt for molecules comprising monolayers. The SAMs prepared from the longest (F10) thiols exhibited the highest degree of ordering with the molecular axis nearly perpendicular to the gold surface. The degree of ordering decreased significantly with decreasing length of the perfluorocarbon tail.

Biophysics↗
NASA NTRS1968

Fluorine-containing polyformals

A fluorine-containing polymeric polyformals is described which has the repeating unit O CH2 O CH2 (CF2) sub n CH2 wherein n is an integer of from about 3 to about 6 prepared by reacting trioxane with a diol having the formula HO CH2 (CF2) sub n CH2 OH. These polymeric polyformals are useful directly for impervious coatings on metals and the like.

Trischler, F. D.↗
NASA NTRS2001

Langmuir Probe and Mass Spectroscopic Measurements in Inductively Coupled CF4 Plasmas

Abstract Electron and ion energy distribution functions and other plasma parameters such as plasma potential (V(sub p)) , electron temperature (T(sub e)), and electron and ion number densities (n (sub e) and n(sub i)) in low pressure CF4 plasmas have been measured. The experiments were conducted in a GEC cell using an inductively coupled plasma (ICP) device powered by a 13.56 MHz radio-frequency (rf) power source. The measurements were made at 300 W of input rf power at 10, 30 and 50 mTorr gas pressures. Langmuir probe measurements suggest that n(sub e), n(sub i) and V(sub p) remain constant over 60% of the central electrode area, beyond which they decrease. Within the limits of experimental error (+/- 0.25 eV), T(sub e) remains nearly constant over the electrode area. T(sub e) and V(sub p) increase with a decrease in pressure. n(sub e) and n(sub i) are not affected as significantly as T(sub e) or V(sub p) by variation in the gas pressure. The electron energy distribution function (EEDF) measurements indicate a highly non-Maxwellian plasma. CF3+ is the most dominant ion product of the plasma, followed by CF2+ and CF+. The concentrations of CF2+ and CF+ are much larger than that is possible from direct electron impact ionization of the parent gas. The cross-section data suggest that the direct electron impact ionization of fragment neutrals and negative ion production by electron attachment may be responsible for increase of the minor ions.

Rao, M. V. V. S.↗
DOE OSTI2020

Materials Data on AgH9C7S2(OF)4 by Materials Project

AgC5H9(SO2)2(CF2)2 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of four difluoromethane molecules and one AgC5H9(SO2)2 cluster. In the AgC5H9(SO2)2 cluster, Ag1+ is bonded in a 5-coordinate geometry to two S2- and three O2- atoms. Both Ag–S bond lengths are 2.49 Å. There are a spread of Ag–O bond distances ranging from 2.72–2.98 Å. There are five inequivalent C+0.86+ sites. In the first C+0.86+ site, C+0.86+ is bonded in a trigonal non-coplanar geometry to three H1+ and one S2- atom. There is one shorter (1.09 Å) and two longer (1.10 Å) C–H bond length. The C–S bond length is 1.81 Å. In the second C+0.86+ site, C+0.86+ is bonded in a trigonal non-coplanar geometry to three H1+ and one S2- atom. All C–H bond lengths are 1.10 Å. The C–S bond length is 1.81 Å. In the third C+0.86+ site, C+0.86+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.24 Å) and one longer (1.28 Å) C–O bond length. In the fourth C+0.86+ site, C+0.86+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.23 Å) and one longer (1.31 Å) C–O bond length. In the fifth C+0.86+ site, C+0.86+ is bonded in a distorted water-like geometry to two H1+ and two S2- atoms. Both C–H bond lengths are 1.10 Å. There is one shorter (1.80 Å) and one longer (1.82 Å) C–S bond length. There are nine inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C+0.86+ atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C+0.86+ atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C+0.86+ atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.86+ atom. In the fifth H1+ site, H1+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.06 Å) and one longer (1.47 Å) H–O bond length. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.86+ atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one C+0.86+ atom. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.86+ atom. In the ninth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.86+ atom. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a distorted trigonal non-coplanar geometry to one Ag1+ and two C+0.86+ atoms. In the second S2- site, S2- is bonded in a trigonal non-coplanar geometry to one Ag1+ and two C+0.86+ atoms. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one Ag1+ and one C+0.86+ atom. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ag1+, one C+0.86+, and one H1+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one Ag1+ and one C+0.86+ atom. In the fourth O2- site, O2- is bonded in a water-like geometry to one C+0.86+ and one H1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AsC2S2(OF3)3 by Materials Project

(CF2)2AsSOF5SO2 crystallizes in the orthorhombic Pnma space group. The structure is zero-dimensional and consists of eight difluoromethane molecules, four sulfur dioxide molecules, and four AsSOF5 clusters. In each AsSOF5 cluster, As5+ is bonded in an octahedral geometry to one O2- and five F1- atoms. The As–O bond length is 2.02 Å. There are a spread of As–F bond distances ranging from 1.74–1.77 Å. S1+ is bonded in a single-bond geometry to one O2- atom. The S–O bond length is 1.55 Å. O2- is bonded in a distorted bent 120 degrees geometry to one As5+ and one S1+ atom. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In the third F1- site, F1- is bonded in a single-bond geometry to one As5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AgH8C7S2O2F7 by Materials Project

AgC4H8(SO)2(CF2)2CF3 crystallizes in the orthorhombic Pca2_1 space group. The structure is two-dimensional and consists of eight difluoromethane molecules; four fluoroform molecules; and one AgC4H8(SO)2 sheet oriented in the (0, 0, 1) direction. In the AgC4H8(SO)2 sheet, Ag1+ is bonded to three S2- and one O2- atom to form distorted corner-sharing AgS3O tetrahedra. All Ag–S bond lengths are 2.62 Å. The Ag–O bond length is 2.35 Å. There are four inequivalent C+0.86+ sites. In the first C+0.86+ site, C+0.86+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.24 Å) and one longer (1.27 Å) C–O bond length. In the second C+0.86+ site, C+0.86+ is bonded in a trigonal non-coplanar geometry to three H1+ and one S2- atom. There is two shorter (1.09 Å) and one longer (1.10 Å) C–H bond length. The C–S bond length is 1.81 Å. In the third C+0.86+ site, C+0.86+ is bonded in a trigonal non-coplanar geometry to three H1+ and one S2- atom. There is two shorter (1.09 Å) and one longer (1.10 Å) C–H bond length. The C–S bond length is 1.82 Å. In the fourth C+0.86+ site, C+0.86+ is bonded in a distorted water-like geometry to two H1+ and two S2- atoms. Both C–H bond lengths are 1.10 Å. There is one shorter (1.81 Å) and one longer (1.83 Å) C–S bond length. There are eight inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C+0.86+ atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C+0.86+ atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C+0.86+ atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.86+ atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.86+ atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.86+ atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one C+0.86+ atom. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.86+ atom. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded to two equivalent Ag1+ and two C+0.86+ atoms to form distorted corner-sharing SAg2C2 tetrahedra. In the second S2- site, S2- is bonded in a distorted trigonal non-coplanar geometry to one Ag1+ and two C+0.86+ atoms. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to one Ag1+ and one C+0.86+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+0.86+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on GeC4(BrF5)2 by Materials Project

GeBr2(CF2)2(CF3)2 crystallizes in the tetragonal P4_32_12 space group. The structure is zero-dimensional and consists of four dibromogermane molecules, eight difluoromethane molecules, and eight fluoroform molecules.

36 MATERIALS SCIENCE↗