- Two-Photon Photochemistry of CS2: Formation of S2 (v2) and CS(v10) at 308 nm
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Room-temperature CS2 is photolyzed at 308 nm in a low-pressure flow cell.Laser-excited fluorescence is used to observe both CS(v10) and S2(v2) products 10μs after the excimer laser pulse.Both products display a quadratic dependence on the excimer laser intensity.These results are consistent with a two-photon excitation of CS2 to a high-lying electronic state (near 154 nm) which predissociated to S and CS, followed by reaction of the S atom with undissociated CS2.
- Sapers, S. P.,Donaldson, D. J.
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- PHOTODISSOCIATION OF (OCS)2 AND (CS2)2: COMPETING PHOTOCHEMICAL PATHWAYS
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The photochemistry of (OCS)2 and (CS2)2 is investigated by using resonance-enhanced multiphoton ionization.The competition between van der Waals and covalent bond chemistry occurring upon electronic excitation of the dimers is probed, and the energetic and kinetic factors affecting this competition are examined.Photodissociation of the 1Σ+ state of OCS in a dimer is investigated and found to produce a significant amount of S2.Photodissotiation of the 1B2(1Σu+) state of CS2 in a dimer leads to the production of S2 and C2S2 photoproducts.These fragments are obtained as a result of covalent bond photochemistry of the respective dimers.There appears to be a greater tendency toward van der Waals bond dissociation in (CS2)2 compared with (OCS)2, in agreement with expectations based on differences in energetics and excited-state dynamics of the two dimers.
- Prinslow, Douglas A.,Vaida, Veronica
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- Thermodynamics of the Zinc Sulphide Transformation, Sphalerite -> Wurtzite, by Modified Entrainment
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The dissociative sublimation of both α- and β-zinc sulphide, ZnS(c) = Zn(g) + 1/2S2(g), has been studied by modified entrainment in the temperature range 1010-1445 K.The following free-energy equation were derived: ΔG0(α)/J mol-1 = 3
- Gardner, Peter J.,Pang, Peter
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- Product energy disposal in the nonadiabatic reaction S(1D) + CS2 --> S2 (X3Σ-g) + CS (X1Σ+)
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The product energy disposal in the reaction S(1D) + CS2 --> S2 +CS is measured via laser-induced fluorescence.Molecular sulphur is produced exclusively in its electronic ground state (3Σ-g) with up to 3 quanta of vibrational excitation and rotational excitation that roughly approximates a 1000 K Boltzmann distribution.The CS produced from the reaction is formed predominantly in its vibrationless state.The total internal energy content of the product molecular sulphur is only about 12percent of the total available energy of the reaction: the CS fragment also has minimal internal energy, implying that most of the reaction energy resides in product translation.These results are different from those observed in the isovalent S + OCS reaction and suggest that a different detailed mechanism is operative.
- Sapers, Steven P.,Andraos, Nancy,Donaldson, D.J.
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- Infrared spectroscopy and 266 nm photolysis of H2S2 in solid Ar
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The infrared spectra of H2S2 and its 266 nm photolysis products are studied in an Ar matrix at 7.5 K. The antisymmetric and symmetric HS-stretching, and the antisymmetric bending of H2S2 are assigned at 2556.6, 2553.8 and 880.3 cm-1, respectively. The absorptions appearing during the photolysis at 2463, 2460 and 903 cm-1 are tentatively assigned to the HS2 radical. The two main dissociation channels are: H2S2+hν → HS2+H and H2S2+hν → S2+H2, with a branching ratio close to 1.
- Isoniemi, Esa,Khriachtchev, Leonid,Pettersson, Mika,Raesaenen, Markku
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- Vapour pressure of solid Bi2S3
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A vaporization study of solid bismuth sulfide, carried out by using two different techniques in the temperatur range 614 to 695 K, showed that this compound vaporizes according to the reaction Bi2S3(s) = 2 Bi(l) + 3/2 S2(g).The resulting pressure-temperature equation for S2(g) is log10(p/Pa) = (15.1 +/- 0.4) - (9540 +/- 250) (K/T).The standard enthalpy of the vaporization process of Bi2S3, ΔH0 (298.15 K) = (254 +/- 10) kJ * mol-1 has been determined as average of values obtained by second- and third-law treatments of the results.
- Piacente, V.,Gianfreda, V. D.,Bardi, G.
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- Thermal analysis of heterocyclic thione donor complexes. Part VII1 1 For Part VI see ref. 1.. Palladium(II) and platinum(II) complexes of thizole-thiolates
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The thermal decomposition of benzothiazoline-2-thiolate, thiazolidine-2-thiolate and thiazoline-2-thiolate complexes of general formula M2L4, where M = Pd and Pt, were studied in air by means of TG and DTG, and by means of DTA in din
- Raper, Eric S.,Britton, Amanda M.,Creighton, James R.
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- Real-time monitoring of a photoactivated hydrogen persulfide donor for biological entities
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Hydrogen persulfide (H2S2) plays an important role in sulfur-based redox signaling mechanisms. Herein, we developed a visible light activated ESIPT based H2S2 donor using a p-hydroxyphenacyl phototrigger. The unique feature of the designed H2S2 donor system is the ability to monitor the H2S2 release in real time through a non-invasive fluorescence color change approach, with the color changing from green to blue. Next, we demonstrated the detection and quantification of H2S2 using a fluorescein based "turn-on" fluorescent probe. Furthermore, in vitro studies of the designed H2S2 donor demonstrated the real-time monitored H2S2 release and cytoprotective ability in the highly oxidizing cellular environment of MDA-MB-468 cells.
- Chaudhuri, Amrita,Venkatesh, Yarra,Jena, Bikash Chandra,Behara, Krishna Kalyani,Mandal, Mahitosh,Singh, N.D. Pradeep
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supporting information
p. 8800 - 8805
(2019/10/22)
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- Alternative pathway of H2S and polysulfides production from sulfurated catalytic-cysteine of reaction intermediates of 3-mercaptopyruvate sulfurtransferase
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It has been known that hydrogen sulfide and/or polysulfides are produced from a (poly)sulfurated sulfur-acceptor substrate of 3-mercaptopyruvate sulfurtransferase (MST) via thioredoxin (Trx) reduction in vitro. In this study, we used thiosulfate as the donor substrate and the catalytic reaction was terminated on the formation of a persulfide or polysulfides. We can present alternative pathway of production of hydrogen sulfide and/or polysulfides from (poly)sulfurated catalytic-site cysteine of reaction intermediates of MST via Trx reduction. Matrix-assisted laser desorption ionization tandem time-of-flight mass spectrometric analysis revealed that after prolonged incubation of MST with thiosulfate, a trisulfide adduct becomes predominant at the sulfurated catalytic-site cysteine. When these adducts were reduced by Trx with reducing system (MST:Escherichia coli Trx:E. coli Trx reductase:NADPH = 1:5:0.02:12.5 molar ratio), liquid chromatography with tandem mass spectrometric analysis for monobromobimane-derivatized H2Sn revealed that H2S2 first appeared, and then H2S and H2S3 did later. The results were confirmed by high-performance liquid chromatography-fluorescence analysis.
- Nagahara, Noriyuki,Koike, Shin,Nirasawa, Takashi,Kimura, Hideo,Ogasawara, Yuki
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p. 648 - 653
(2018/01/27)
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- Formation of Mo and MoSx nanoparticles on Au(1 1 1) from Mo(CO)6 and S2 precursors: Electronic and chemical properties
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Mo(CO)6 can be useful as a precursor for the preparation of Mo and MoSx nanoparticles on a Au(1 1 1) substrate. On this surface the carbonyl adsorbs intact at 100 K and desorbs at temperatures lower than 300 K. Under these conditions, the dissociation of the Mo(CO)6 molecule is negligible and a desorption channel clearly dominates. An efficient dissociation channel was found after dosing Mo(CO)6 at high temperatures (400 K). The decomposition of Mo(CO)6 yields the small coverages of pure Mo that are necessary for the formation of Mo nanoclusters on the Au(1 1 1) substrate. At large coverages of Mo (0.15 ML), the dissociation of Mo(CO)6 produces also C and O adatoms. Mo nanoclusters bonded to Au(1 1 1) exhibit a surprising low reactivity towards CO. Mo/Au(1 1 1) surfaces with Mo coverages below 0.1 ML adsorb the CO molecule weakly (desorption temperaturex nanoparticles. The formed MoSx species are more reactive towards thiophene than extended MoS2(0002) surfaces, MoSx films or MoSx/Al2O3 catalysts. This could be a consequence of special adsorption sites and/or distinctive electronic properties that favor bonding interactions with sulfur-containing molecules.
- Rodriguez, José A.,Dvorak, Joseph,Jirsak, Tomas,Hrbek, Jan
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p. 315 - 326
(2008/10/08)
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- Low-temperature thermoluminescence in solid argon: Short-range mobility of atoms
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The 193-nm photolysis of S2 (produced from H2S2) and SO2 in solid argon and the changes introduced by annealing are monitored by using Fourier-transform infrared spectroscopy and laser-induced fluorescence. The results highlight short-range atomic mobility distinguished from global long-range mobility. It is shown that under the 193-nm irradiation a small part of S2 and SO2 molecules undergo photodecomposition yielding quasi-isolated pairs where the fragments are in close vicinity to each other. In annealing, the short-range mobility results in recombination of these pairs at rather low temperatures (a static Ar lattice support this scenario, demonstrating that the photofragments can be gently separated by a low potential barrier which favors their recombination in annealing. In particular, this quasistable configuration occurs when the two atoms occupy substitutional sites separated by the lattice parameter of 5.31 A.
- Khriachtchev, Leonid,Pettersson, Mika,Pehkonen, Susanna,Isoniemi, Esa,Raesaenen, Markku
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p. 1650 - 1657
(2007/10/03)
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- S2 (a 1Δ ) production in the photolysis of reduced sulfides: Production chemistry, spectroscopy and interference potential in the LIF detection of OH
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Production of S2 (a 1Δ, v=2) has been observed in the UV photolysis of several reduced sulfur compounds by monitoring the f 1Δ-a 1Δ (2-3) laser excitation spectrum. There appears to be at least three production mechanisms including reaction of S (1D) with the precursor. The f-a (2-3) band shows several spectral overlaps with the OH A 2Σ-X 2Π (1-0) band including the Q11 line. Since a significant fraction of the f-a emission from f 1Δ (v=2) overlaps the OH A-X (1-1) and (0-0) bands the potential for a significant 'interference' signal exists if the two species are produced simultaneously.
- Hynes,Richter,Rosendahl,Clark
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- The adsorption of sulfur on Rh(111) and Cu/Rh(111) surfaces
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The reaction of S2 with Rh(111) and Cu/Rh(111) surfaces has been investigated using synchrotron-based high-resolution photoemission, thermal desorption mass spectroscopy and ab initio self-consistent-field calculations. At 100 K, the adsorption of S2 on Rh(111) produces multilayers of Sn species (n = 2-8) that desorb between 300 and 400 K, leaving a film of RhSx on the sample. S2 dissociates upon adsorption on clean Rh(111) at 300 K. An adsorption complex in which S2 is bridge bonded to two adjacent Rh atoms (Rh-S-S-Rh) is probably the precursor state for the dissociation of the molecule. The larger the electron transfer from Rh(111) into the S2(2πg) orbitals, the bigger the adsorption energy of the molecule and the easier the cleavage of the S-S bond. On Rh(111) at 300 K, chemisorbed S is bonded to two dissimilar adsorption sites (hollow and probably bridge) that show well separated S 2p binding energies and different bonding interactions. Adsorption on bridge sites is observed only at S coverages above 0.5 ML, and precedes the formation of RhSx films. The bonding of S to Rh(111) induces a substantial decrease in the density of d states that the metal exhibits near the Fermi level, but the electronic perturbations are not as large as those found for S/Pt(111) and S/Pd(111). Cu adatoms significantly enhance the rate of sulfidation of Rh(111) through indirect Cu?Rh?S2 and direct Cu?S-S?Rh interactions. In the presence of Cu there is an increase in the thermal stability of sulfur on Rh(111). The adsorption of S2 on Cu/Rh(111) surfaces produces CuSy and RhSx species that exhibit a distinctive band structure and decompose at temperatures between 900 and 1100 K: CuSy/RhSx/Rh(111)→S2(gas) + Cu(gas) + S/Rh(111).
- Rodriguez, Jose A.,Chaturvedi, Sanjay,Kuehn, Mark
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p. 3064 - 3073
(2007/10/03)
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- The bonding of sulfur to Pd surfaces: Photoemission and molecular-orbital studies
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The adsorption and dissociation of S2 on Pd(111) and polycrystalline Pd were studied using synchrotron-based high-resolution photoemission spectroscopy and ab initio SCF calculations. The photoemission results show several sulfur species with distinct electronic properties. The formation of Pd-S bonds induces large positive binding-energy shifts in the core and valence levels of Pd. After chemisorbing sulfur on the Pd surfaces, there is a substantial decrease in the electron density that the metal exhibits near the Fermi level and a simultaneous drop in the electron population of its 4d band. Pd is more sensitive to sulfur than other metals frequently used in automotive exhaust catalysts (Rh and Pt).
- Rodriguez, Jose A.,Chaturvedi, Sanjay,Jirsak, Tomas
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p. 421 - 428
(2008/10/08)
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- Reaction of H2S and S2 with metal/oxide surfaces: band-gap size and chemical reactivity
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The adsorption and dissociation of H2S and S2 on a series of oxide (Al2O3, Cr2O3, Cr3O4, Cu2O, ZnO) and metal/oxide (Cu/Al2O3, Cu/ZnO) surfaces have been studied using synchrotron-based high-resolution photoemission. H2S and S2 mainly interact with the metal centers of the oxides. At 300 K, H2S undergoes complete decomposition. The rate of decomposition on Al2O3 is much lower than those found on Cr3O4, Cr2O3, ZnO, and Cu2O. For these systems, the smaller the band gap in the oxide, the bigger its reactivity toward S-containing molecules. The results of ab initio SCF calculations for the adsorption of H2S, HS, and S on clusters that resemble the (0001) face of α-Al2O3, α-Cr2O3, and ZnO show that the S-containing species interact stronger with Cr or Zn than with Al centers. These theoretical results and the trends seen in the experimental data indicate that the reactivity of an oxide mainly depends on how well its bands mix with the orbitals of H2S or HS. The electrostatic interactions between the dipole of H2S and the ionic field generated by the charges in the oxide play only a secondary role in the adsorption process. Photoemission results show that the rate of adsorption of H2S and S2 on Cu/Al2O3 and Cu/ZnO surfaces is much faster than on the pure oxides. A simple model based on perturbation theory and orbital mixing is able to explain the effects of the band-gap size on the reactivity of an oxide and the behavior of metal/oxide surfaces in the presence of S-containing molecules.
- Rodriguez,Chaturvedi,Kuhn,Hrbek
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p. 5511 - 5519
(2008/10/08)
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- Reaction of S2 with ZnO and Cu/ZnO surfaces: Photoemission and molecular orbital studies
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The adsorption of S2 on ZnO and Cu/ZnO has been investigated using synchrotron-based high-resolution photoemission spectroscopy. On dosing a clean ZnO surface with S2 at 300 K, the molecule dissociates. The S is associated first with Zn and at medium coverages with Zn-O sites. When the sulfur coverage is increased to θs = 0.5 ML, evidence is found for sulfur bound purely to the O sites of ZnO. The sulfur species associated with O and the Zn-O sites are unstable at temperatures above 500 K. Possible reaction pathways for the dissociation of S2 on ZnO(0001)-Zn and Zn(1010) surfaces were studied using ab initio SCF calculations. At low sulfur coverages, an adsorption complex in which S2 is bridge bonded to two adjacent Zn atoms (Zn-S-S-Zn) is probably the precursor state for the dissociation for the molecule. It is possible to get much higher coverages of sulfur on ZnO (0.7 ML) than on Al2O3 (0.1 ML) at similar S2 exposures. This, in conjunction with results previously reported for H2S adsorption on Cr2O3 and Cr3O4, indicates that the reactivity of metal oxides toward sulfur is inversely proportional to the size of their band gap. Oxides with a large band gap (e.g., Al2O3, ~9.0 eV) are less susceptible to sulfur adsorption than oxides with a small band gap (e.g., ZnO, ~3.4 eV). The presence of Cu atoms on both metal oxides enhances their respective reactivities toward S2. Upon dosing Cu/ZnO with S2 at 300 K, sulfur prefers to attack supported Cu followed by reaction with the Zn sites of the oxide, and at large sulfur coverages the adsorbate bonds simultaneously to metal and oxygen sites on the surface. The sulfur bonded to both the metal and oxygen sites on the surface is relatively weakly bound and desorbs by 500 K. The Cu ?? S interactions are strong and lead to the formation of copper sulfides that exhibit a distinctive band structure and decompose at temperatures above 700 K.
- Chaturvedi, Sanjay,Rodriguez, Jose A.,Hrbek, Jan
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p. 10860 - 10869
(2007/10/03)
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- Adsorption of sulfur on Ag/Al2O3 and Zn/Al2O3 surfaces: Thermal desorption, photoemission, and molecular orbital studies
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The interaction of S2 with Ag/Al2O3 and Zn/Al2O3 surfaces has been investigated using thermal desorption mass spectroscopy, core- and valence-level photoemission, and ab initio self-consistent-field calculations. The sticking coefficient of S2 on clean alumina is small (2/Al2O3 system, there is an energy mismatch between the orbitals of the molecule and the bands of the oxide, and the reactivity of S2 on pure alumina is very low. The adsorption of sulfur on Ag/Al2O3 and Zn/Al2O3 surfaces induces strong perturbations in the electronic properties of the admetals and oxide support. In the Ag/Al2O3 and Zn/Al2O3 systems, the supported metal clusters (or particles) provide a large number of electronic states that are very efficient at donating charge into the S2(2πg) orbitals, inducing in this way the breaking of the S-S bond and the formation of admetal sulfides (AgSx and ZnSy). The larger the electron transfer from the supported metal into the S2(2πg) orbitals, the bigger the adsorption energy of the molecule and the easier the cleavage of the S-S bond. The AgSx and ZnSy species decompose at temperatures between 750 and 900 K following two different reaction pathways: AgSx,solid → S2,gas + Agsolid and ZnSy,solid → S2,gas + Zngas.
- Rodriguez, José A.,Kuhn, Mark
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p. 3187 - 3195
(2007/10/03)
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- A deperturbation analysis of the B3∑u- =(v′ = 0-6) and the B″ 3∏u(v′ = 2-12) states of S2
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Laser-induced fluorescence spectra of 32S2 have been obtained, covering v′=0-6 of the B 3-∑u- X 3∑g- transition and v′=2-12 of the B″ 3∏u-X 3∑g- transition, using static cell and supersonic free jet techniques. The spectra include transitions to the previously unseen B″ 3∏2,u components. Analysis of the many perturbations between the two upper electronic states has been carried out using a Hamiltonian matrix including all the B and B″ states simultaneously rather than deperturbing individual pairs of vibronic states. This takes into account longer range interactions and gives deperturbed molecular constants that vary smoothly with vibrational state. Our model for the B″ v′ = 2-12 and B v′=0-6 levels covering J up to 100 can fit all 3320 observed transitions with an average error of 0.064 cm-1. The widely ranging fluorescence lifetimes of the B″ state vibronic levels provide independent information about the state mixing and confirm the model, since the observed B″-X fluorescence arises almost entirely via this mixing. However, lifetime measurements of the newly observed Ω=2 components of the B″ state showed little variation in lifetimes, about an average of 4.2±0.4 μs. This indicates a small intrinsic B″-X transition strength as the Ω=2 components are essentially not mixed with the B state. A model for the perturbation parameters is developed, based on Franck-Condon factors between the two states. The magnitude of the perturbations and transition moments are discussed in relation to the electronic configurations of the B and B″ states. 1996 American Institute of Physics.
- Green,Western
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p. 848 - 864
(2007/10/03)
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- Study on sulfur vaporization from covellite (CuS) and anilite (Cu1.75S)
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Covellite decomposes according to the reaction: 4.667CuS → 2. 667Cu1.75S(s) + S2(g). The sulfur vapour pressures measured in the temperature range 551.5-627 K by the torsion-effusion method are represented by the equation; log p (kPa
- Brunetti, B.,Piacente, V.,Scardala, P.
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p. 113 - 120
(2008/10/08)
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- Chemistry and thermodynamics of solid and vapor phases in the barium-sulfide, gallium-sulfide system
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The technologically important BaS-Ga2S3 solid system was studied and interpreted with a generalized acid-base theory counting BaS(s) as a strong base and Ga2S3(s) as an acid. The strongest bonding in any MS-Ga2S3 system was found. Vaporization of solid samples whose initial composition was BaGa2S4(s) was studied in the temperature range 1234-1361 K by the simultaneous Knudsen-effusion and Volmer-effusion methods. The sample vaporized incongruently and the composition of the solid changed successively to yield a number of phases The vaporization reactions and the average third-law ΔvH°(298 K) in kJ are presented, as well as the enthalpies of ternary phases with respect to those of the binary constituents BaS(s) and Ga2S3(s) in kJ per mole of Ga2S3.
- Mukdeeprom-Burckel,Edwards
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p. 163 - 172
(2008/10/08)
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- Incongruent effusion of ZnGa8S13(s)
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The chemistry and thermodynamics of vaporization in a Knudsen effusion cell of the phase ZnGa8S13 was studied in the range 1115 - 1246 K where the vapor pressure ranged from 0.25 to 10.0 Pa. Samples prepared by sealed-tube methods and characterized by X-ray diffraction were studied by the simultaneous Knudsen and torsion (Volmer) effusion method. ZnGa8S13(s) effused incongruently in equilibrium with a saturated solid solution (sss) of ZnS in Ga2S3, Ga2S(g), Zn(g), and S2(g), always on the ZnS-Ga2S3 join. Ga2S3(sss) then effused with net loss of ZnS to the vapor until the composition of Ga2S3 was reached. Vapor analysis by combining measured rates of mass loss and momentum loss allowed analysis of the vapor and calculation of equilibrium constants of the effusion equations.
- Edwards, Jimmie G.,Ferro, Daniela,Weber, J. K. Richard
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p. 369 - 386
(2008/10/08)
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- Vaporization and Stability of Phases in the SrS-Ga2S3 System
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Vaporization of solid samples whose initial composition was SrGa2S4 were studied in the temperature range 1256-1364 K by the simultaneous Knudsen- and torsion-effusion methods.The effusing vapor was taken to be composed of Ga2S(g) and S2(g) in equimolar a
- Kapias, Piotr,Edwards, Jimmie G.
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p. 3649 - 3656
(2007/10/02)
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- State-resolved photodissociation of OCS monomers and clusters
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Photodissociation of OCS in the region from 222-248 nm has been investigated by monitoring the CO and S(1D2) primary photoproducts; as well as the secondary production of S(3P2), S(3P1), and S(3P0) using fluorescence induced by a tunable vacuum ultraviolet laser source based on four-wave mixing in magnesium vapor.The quantum yield of S(3P) was found to be 0.00 +/- 0.02 at 222 nm.Thus, in contrast to our preliminary report, the present more detailed investigation shows that the sole sulfur product appears to be S(1D).The CO photofragment is produced almost exclusively in ν = O 0.02>, but the rotational distribution is inverted and peaked at very high rotational levels.The peak shifts from J = 56 for dissociation at 222 nm to J = 31 at 248 nm.Doppler profiles of the CO rotational transitions reveal ( I ) that all observed levels are produced in coincidence with S (1D), (2) that for 222 nm photolysis the fragment recoil anisotropy shifts from a distribution characterized by β = 1.9 at J = 67 toward one characterized by β = O near J = 54, ( 3 ) that the CO velocity vector is aligned nearly perpendicular to its angular momentum vector, and (4) that the CO angular momentum vector is also aligned parallel to that component of the transition dipole which lies perpendicular to the recoil velocity.These results are interpreted in terms of a model for the dissociation in which excitation takes place to two surfaces of A ' and A N symmetry derived from a bent 1D configuration.Dissociation of OCS clusters was also investigated and was found to produce a photochemistry completely different from that of the monomers.Rotationally cold CO as well as S2 in both the X 3Σ-g and a1 δsg states was observed.
- Sivakumar, N.,Hall, G. E.,Houston, P. L.,Hepburn, J. W.,Burak, I.
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p. 3692 - 3708
(2007/10/02)
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- Vaporization of (SN)x: He I Photoelectron Spectrum and ab Initio Calculations for the S3N3 Radical
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The S3N3 radical, never previously characterized, is shown to be the major semistable component of the vaporization products of the (SN)x polymer, as identified by He I photoelectron spectroscopy and in situ quadrupole mass spectrometry.This species can be recondensed to yield the (SN)x polymer and other colored materials.Revaporization produces S3N3 in addition to S4N4, S4N2, and S2N2.Ab initio calculations with better than a double-ζ basis set and including configuration interaction provide evidence for a 2A2 radical with a planar ring geometry close to D3h.The ground-state cation also has a planar ring geometry with 3A2' favored over 1A1'.
- Lau, W. M.,Westwood, N. P. C.,Palmer, M. H.
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p. 3229 - 3237
(2007/10/02)
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- INFLUENCE OF THE REACTION MEDIUM ON THE PROPERTIES OF CARRIER-SUPPORTED OXIDE CATALYSTS IN THE REDUCTION OF SULFUR DIOXIDE WITH CARBON MONOXIDE.
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The results of this investigation show that the catalysts are partially reduced during their formation in a stream of the reaction mixture. The degree of reduction of SO//2 with carbon monoxide hereby increases. The formation of catalysts in a stream of the reaction mixture at elevated temperatures enhances their activation: A counterclockwise hysteresis is observed on the curve representing the activity as a function of temperature. A reaction of the carbon monoxide with oxygen on the catalyst surface precedes the reaction of CO with sulfur dioxide. Oxygen inhibits the reduction of SO//2 by carbon monoxide; carbon dioxide has no effect on the reaction rate.
- Zanevskaya,Denisov,Vlasenko,Raksha
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p. 2234 - 2238
(2008/10/08)
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- STUDY OF THE GAS PHASE DURING REDUCTION OF MAGNESIUM SULFATE BY GASEOUS REDUCTANTS.
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Theoretical and experimental studies of the gas phase during reduction of magnesium sulfate by gaseous reductants (methane, hydrogen, and carbon monoxide) showed that oxidation of the reductants occurs predominantly with formation of CO//2 and H//2O. Under the conditions of sulfate reduction the principal volatile sulfur-containing product is elemental sulfur. The yields of elemental sulfur, hydrogen sulfide, and sulfur dioxide depend on the amounts of reductants, their variations with time, the reduction conditions, and rates of cooling of the gaseous products. The yield of elemental sulfur is lowered mainly by its interaction with water vapor and as the result of presence of excess reductant during cooling of the gaseous products.
- Kriklivyi,Klimovich,Shpak
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p. 2241 - 2247
(2008/10/08)
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- STUDY OF THE DISPROPORTIONATION OF SODIUM THIOSULFATE BY X-RAY PHOTOELECTRON SPECTROSCOPY.
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The disproportionation of sodium thiosulfate to form sodium sulfite and elemental sulfur has been studied in the temperature range 495-548 degree K by means of X-ray photoelectron spectroscopy (XPS). The disproportionation started with an induction period, followed by a steady-state disproportionation rate regime, and ended up with a diffusion rate-controlling process. The duration of the induction period was inversely proportional to the temperature of heating. The disproportionation in the steady-state regime followed a first-order reaction rate law with the enthalpy and entropy of activation H* equals 26. 0 kcal/mol and S* equals minus 14. 9 eu.
- Xu,Chang
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p. 165 - 170
(2008/10/08)
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- Thermochemical Splitting of Sulfur Dioxide with Cerium(IV) Oxide
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Ce2(SO3)2SO4*4H2O thermally decomposes in several steps to yield H2O, sulfur, SO2, and O2 as gaseous products, plus Ce2O(SO4)2, Ce2O2SO4, CeOSO4, and CeO2 as intermediate products.The terminal solid product above 1250 K is CeO2.Reaction pathways are described in detail.A thermochemical cycle for splitting SO2 into sulfur and oxygen with CeO2 is described, in which sulfur and/or oxygen and /or cerium all change valence in four different reactions.
- Peterson, E. J.,Foltyn, E. M.,Onstott, E. I.
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p. 7572 - 7573
(2007/10/02)
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- Reactivity of Fe2O3 and Fe2O3-Al2O3 Mixture for Reduction of SO2 with CO
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Catalytic reactivities of α-Fe2O3 powder (-200 mesh) and a α-Fe2O3-γ-Al2O3 powder mixture prepared by mechanical mixing, which were preheated at 360-700 deg C, were studied for the reduction of SO2 with CO by means of both a reaction gas-chromatographic technique using CO, SO2, and 2CO-SO2 pulses and the powder X-ray analysis.The reactivity of Fe2O3 decreases with increasing preheating temperature, which is explained on the basis of redox reactions between Fe2O3 and nascent (Fe3O4): 6Fe2O3+2CO->4(Fe3O4)+2CO2 and 4(Fe3O4)+SO2->6Fe2O3+1/2S2.It is considered that the reactivity of Fe2O3 is attributable to the activity of (Fe3O4).The lifetime of active (Fe3O4) is within about 1 min, and the activity and lifetime of (Fe3O4) is increased by interfacial reaction between Fe2O3 and Al2O3 at 700 deg C.The activity maximum in the Fe2O3-Al2O3 system preheated at 700 deg C is attained at 70-75 wtpercent Fe2O3.
- Ishii, Tadao,Furuichi, Ryusaburo,Shikano, Koji
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p. 1447 - 1453
(2007/10/02)
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- UV and visible emission produced from S2Cl2 in the rare gas flowing afterglow
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The energy transfer reactions of metastable Ar(3P0,2), Ne(3P0,2), and He(2 3S) atoms with S2Cl2 have been studied by optical spectroscopy in a flowing afterglow apparatus.In the Ar(3P0,2) + S2Cl2 reaction, ArCl*, S2(B-X), and Cl2* emissions were observed, whereas SI and Cl2* emissions were detected in the Ne(3P0,2) + S2Cl2 reaction.The He(2 3S) + S2Cl2 reaction produced a new extensive S2+ (A 2Πu -X 2Πg,r) emission in the 350-700 nm region, in addition to SI, ClI, and Cl2* emissions.Vibrational analysis of the S2+(A-X) band system provided molecular constants of the S2+(A, X) states.By using these constants, Morse potential Franck-Condon factors and r centroids of the S2+(A-X) transition have been calculated.The relative electronic transition moments and vibrational populations of S2+(A) have also been determined.The vibrational populations for 0 v' 6 were nearly exponential with an effective vibrational temperature of 1020 +/- 50 K.
- Tsuji, Masaharu,Murakami, Isao,Nishimura, Yukio
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p. 5373 - 5380
(2007/10/02)
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- Vaporization Chemistry, Kinetics, and Thermodynamics of Compounds in the Manganese Monosulfide-Gallium Sesquisulfide System
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The vaporization reactions of MnGa2S4(s) and Mn3Ga2S6(s) were established to be 3/2 MnGa2S4(s)=1/2 Mn3Ga2S6(s) + Ga2S(g) + S2(g) and Mn3Ga2S6(s)=3MnS(s) + Ga2S(g)+ S2(g) in the temperature range 1150-1315 K.The simultaneous Knudsen-effusion and dynamic to
- Gates, Alfred S.,Edwards, Jimmie G.
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p. 3263 - 3270
(2007/10/02)
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- The preparation, properties, and crystal structures of some scandium sulfides in the range Sc2S3-ScS
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Scandium sesquisulfide, Sc2S3, was prepared by the high-temperature reaction of hydrogen sulfide with scandium sesquioxide. Due to the problem of stoichiometry associated with the high melting point, 1775°, stoichiometric crystals of Sc2S3 were prepared by chemical transport with I2 at 950°. A nonstoichiometric material containing an excess of scandium compared with Sc2S3 was prepared by heating Sc2S3 under vacuum at 1650°. Crystals of ScS were prepared by the reaction of scandium metal with sulfur. The crystal structure of Sc2S3 is closely related to that of NaCl, but the unit cell is twelve times as large due to a complex ordering arrangement of the cation voids. Each octahedron surrounding sulfur has two vertices empty, and the bond angles are all very close to 90°. The nonstoichiometric material has a much simpler structure which is also closely related to that of NaCl, with Sc1.37S2 per rhombohedral unit cell. This structure, in which one cation site is filled and the other is only partially occupied, could exist over the whole range between Sc2S3 and ScS, which was found to have the NaCl structure. Stoichiometric Sc2S3 is a semiconductor with a band gap of about 2 e.V., but the materials between Sc2S3 and ScS are good electrical conductors. Electrical conduction in the latter materials appears to involve a 3d band.
- Dismukes,White
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p. 1220 - 1228
(2008/10/08)
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