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The four-center reaction F2 + Na2 ---> F + NaF + Na(32P) has been studied in a crossed molecular-beam experiment.The excitation function for the production of this electronically excited state has been measured over two ranges of collisiomn energy -5.8-6.8 and 9.4-15.4 kcal/mol.This cross section has been scaled for comparison with that of the three-center reaction F + Na2 ---> NaF + Na*(32P) (see the experimental results reported in the preceeding paper in this issue).The three-center reaction cross section to form Na*(32P) is also a rising function of collision energy.The three-center reaction to form Na*(32P) is connected adiabatically to the ground reactant state while the four-center reaction increases from ca. 1 to 8 Angstroem2, while that for the three-center reaction increases from ca.4 to 125 Angstroem2.Both reactions appear to involve a barrier to the production of the Na*(32P).In the case of four-center reaction, the steeply rising excitation function may result from the changing nonadiabatic behavior with increasing collision energy.

Chemiluminescence from the reaction F + Na2 ---> NaF + Na*(i) has been measured for six electronically excited states of Na: the upper state of the D line, 32P, and the more energetic states i=32D, 52S, 42D, 6s

A crossed-molecular-beam study has been performed of the three-center reaction F + Na2 ---> NaF + Na(i). The relative cross sections for producing many of the electronic states of Na ( states i ranging from 32P to 72P) have been measured at two collision energies 4.7 and 122.8 kcal/mol.The crosss sections decreased rapidly with increasing electronic excitation, the falloff being less steep at higher collision energy.The excitation function for populating the 32P state was measured and found to increase with increasing collision energy, suggesting tha presence of a barrier to the production of this lowest electronically excited state.The barrier height for this pathway was 4.5 kcal/mol.The excitation function for 32D, 52S, and 42D states could be inferred from the measured relative cross sections; they also increased with increasing collision energy.We have performed phase space and information theory calculations at the same level of approximation to obtain distributions over electronically excited states of sodium reaction products and have compared these with experimental results.Information theory predicts a much more rapid decrease in the cross sections with increassing electronic excitation than does the phase space theory.Comparing the experimental results with phase space theory, we find that, for enhanced reagent collision energy, the distribution of the reaction product over electronically excited states is nonstatistical.In particular the first excited state (32P) is populated at at rate an order of magnitude greater than would be expected from statistical considerations.Higher states are formed in an approximately statistical distribution.The observed dynamical bias may originate in the fact that only the 32P state can be accessed by an adiabatic pathway.

Porous carbon materials with pore sizes from 3 to 200 nm were synthesized by reacting hexafluorobenzene with Na liquid at 623 K. NaF crystals, a byproduct formed in the reaction, acted as nanotemplate to assist the pore formation. By employing hexafluorobenzene to react with Na incorporated within the channels (diameter 200 nm) of anodized aluminum oxide (AAO) membranes at 323-623 K, the carbon material can be fabricated into aligned porous nanotube arrays (ca. 250 nm in diameter, ca. 20 nm in wall thickness, ca. 0.06 mm in length, and ca. 3-90 nm in pore diameter). These materials were characterized by X-ray diffraction, scanning and transmission electron microscopy, X-ray energy dispersive spectroscopy, electron diffraction, thermal gravimetric analysis, and nitrogen physical adsorption experiments.

The chemiluminescent reaction products of the (Na,Na2)+Br halogenation system at concentrations in excess of 1012 cm-3 are considered. In a purely reaction driven environment evidence is obtained for the formation of the Na2 23Πg excited state and bound-free emission associated with the 23Πg-13Σu+ band system.

An experimental investigation of the fragmentation mechanisms of Na+3 cluster ions in collision with He atoms at 263 eV centre-of-mass energy is presented. The relative populations of the three fragmentation pathways are determined. In particular, the kinematics of the three-body breakup is studied in detail. The analysis of the correlation between the velocity vectors of the fragments allows one to estimate the relative role of the electronic excitation or momentum transfer in the population of each pathway. The discussion of the fragmentation dynamics is based on a concomitant theoretical study.

Confirming experiments of Walker et al. and Hart et al., we show by flash photolysis and pulse radiolysis that the decay of hydrated electrons in aqueous alkaline solutions leads to an intermediate which by illumination with soft UV light (λ > 250 nm) rev

Studies on ternary phase diagrams of the Na-Fe-O system have been carried out from the thermodynamic point of view. Thermodynamic data of main ternary Na-Fe oxides Na4FeO3(s), Na3FeO3(s), Na5FeO4(s) and Na8Fe2O 7(s) have been assessed. A user database has been created by reviewing literature data together with recent DSC and vapor pressure measurements by the present authors. New ternary phase diagrams of the Na-Fe-O system have been constructed from room temperature to 1000 K. Stable conditions of the ternary oxides at 800 K were presented in predominance diagram as functions of oxygen pressure and sodium pressure.

Reacting Ba and N2 in the stoichiometric ratio 6 : 1 at 670 K, homogenizing the product at 570 K in the presence of Na and subsequently distilling off the Na yields Ba3N. This new subnitride decomposes into Ba2N and Ba at 830 K. Its structure represents a hexagonal rod packing of Ba6/2N chains (anti-TiI3 type, space group P63/mcm; a = 764.18(2) pm, c = 705.01(5) pm; Ba in 6 g with x = 0.2721(2), N in 2 b). The peculiarity of a very spaceous packing of these rods is addressed and discussed as possibly due to a quantum size effect.

Chemical bonding in glass-to-metal combination was investigated for maximum adherence conditions. Thermogravimetric and sessile drop measurements were used to study kinetics of redox reactions between sodium disilicate glass and iron. This study was undertaken to evaluate the nature of the reactions between iron and sodium disilicate (NS//2) as a function of time, temperature, and nature of the ambient atmosphere.

The potential syntheses of pure nitrogen materials may involve photolysis of azide compounds. In this work, compressed solid samples of NaN3 were photolyzed in gem anvil cells at pressures up to 5.0 GPa. Reaction rates and mechanisms for the photolytic processes were studied using single-shot time-resolved (microsecond scale) absorption spectroscopy. Two broad absorption bands due to reaction intermediates were observed at 300 and 700 nm. Tentative assignments of the reaction intermediates and their reaction rates were used to help elucidate the potential for high-pressure syntheses of novel nitrogen structures. Finally, recovered products were analyzed with infrared and Raman vibrational spectroscopy.

The fluorescence of excited species formed in collisions between neutral magnesium atoms and sodium ions has been studied experimentally using a crossed ion-atom beam technique. The only emission detected corresponded to the Na(32P3/2,1/2)→Na(32S1/2) decay of neutral Na atoms formed by electron capture. Its strength has permitted to resolve it into its J=1/2 and J=3/2 states, and for the latter the Mj magnetic states have also been separated, cross-section dependence on collision energy or branching ratio being given for all of them.

Vaporization behavior of Na4FeO3(s) was thermodynamically studied from 590 to 717 K by means of high temperature mass spectrometry. It was found that Na4FeO3(s) decomposed into Na3FeO3(s) a

Platinum (Pt)/activated-carbon catalysts were prepared and characterized by pore-size distribution (PSD), propane-sorption dynamics, and activity of cyclohexane dehydrogenation to benzene. The batch-type frequency-response (FR) spectroscopic technique was applied to determine the mass-transport rate of propane sorption. Two parallel sorption processes of different time constants were distinguished, suggesting that adsorption proceeds in smaller and larger micropores that are not interconnected. Increasing Pt loading affected the propane mobility, but increased the dehydrogenation activity only up to ca. 1 wt-% of Pt content. It was concluded that clusters of metallic Pt-atoms are located preferentially at the narrowest pores. Blocking these micropores, the Pt reduces the carbon surface available for sorption; also, a significant fraction of the metal becomes inaccessible for the reactant.

Dark-blue sodium nitride, Na3N, was prepared by the reaction of metallic sodium or liquid Na-K alloy with plasma-activated nitrogen at low pressure. The compound crystallizes in the cubic anti-ReO3-type structure (space group Pm3m with a = 4.73301(6) A and Z = 1) according to powder and single-crystal X-ray diffraction data. Na3N decomposes above 104°C into the elements, with ΔHf estimated at +64(2) kJ/mol.

The reactions xLiNH2 + (1 - x)LiBH4 and xNaNH2 + (1 - x)NaBH4 have been investigated and new phases identified. The lithium amide-borohydride system is dominated by a body centred cubic compound of formula Li4BH4(NH2)3. In the sodium system, a new hydride of approximate composition Na2BH4NH2 has been identified with a primitive cubic structure and lattice parameter a ≈ 4.7 ?. The desorption of gases from the two amide-borohydrides on heating followed a similar pattern with the relative proportions of H2 and NH3 released depending critically on the experimental set-up: in the IGA, ammonia release occurred in two steps - beginning at 60 and 260 °C for Li4BH4(NH2)3 - the second of which was accompanied by hydrogen release; in the TPD system the main desorption product was hydrogen-again at 260 °C for Li4BH4(NH2)3 accompanied by around 5% ammonia. We hypothesize that the BH4- anion can play a similar role to LiH in the LiNH2 + LiH system, where ammonia release is suppressed in favour of hydrogen. The reaction xLiNH2 + (1 - x)LiAlH4 did not result in the production of any new phases but TPD experiments show that hydrogen is released from the mixture 2LiNH2 + LiAlH4, over a wide temperature range. We conclude that mixed complex hydrides may provide a means of tuning the dehydrogenation and rehydrogenation reactions to make viable storage systems.

NaSnN with the non-centrosymmetric layered structure type of KSnAs and featuring the new layered Zintl ion [SnN]- is the first example of a ternary nitride containing Sn-N bonds, and the first example of a nitride containing formally divalent tin. The Royal Society of Chemistry 2005.

Disclosed herein is an improved method for regenerating materials from a desulfurization/demetallation reaction. The desulfurization/demetallation reaction preferably has products including one or more of an alkali sulfide, polysulfide or hydrosulfide, or alkali earth sulfide, polysulfide, or hydrosulfide. The method includes the steps of reacting the desulfurization/demetallation products with a halogen, liberating and removing sulfur from the product, and then electrolyzing the halogenated products to separate the halogen from the alkali metal or alkali earth metal.

Reactions between alkaline earth metals or their corresponding nitrides and NaN3 as nitrogen donor in cleaned sealed Nb ampoules at different temperatures yields known phases, 'β-Ca3N2' and single crystals in the form of transparent, orange plates of Ba 5[NbN4]N. The crystal structure of this new compound was determined by means of single crystal X-ray diffraction (C2/m (no. 12), a = 1231.7(3), b = 1094.6(2), c = 853.8(2) pm,β = 113.65(3) and Z = 4). At temperatures ≥ 1000°C, the available nitrogen apparently reacts with the Nb container walls and intermetallic phases are formed. The crystal structures of AeMg2 (MgZn2 type with Ae = Ca, Yb, Sr, Eu and Ba) were re-determined by X-ray single crystal structure analyses on crystals obtained in such reactions to ascertain the presence or absence of nitrogen in structural voids. The structures of the ternary nitride and intermetallic phases are described and compared to known compounds.

Carbon is commonly added to sulfate-fined silicate-glass batches to enhance the fining process. Reactions between carbon and Na2SO4 modify the SOx emissions from Na2SO4 decomposition. Fourier-transform infrared (FTIR) spectrometry is used to analyze the emission of air pollutants from the isothermal decomposition of Na2SO4 + C undertaken using thermogravimetric analysis (TGA). The FTIR spectrometer is calibrated using standard gas mixtures containing CO, CO2, SO2, NO, and NO2. The collected spectra are quantified using the classical least-squares (CLS) approximation. The TGA-FTIR system provides SOx and COx concentrations versus time data from the isothermal decomposition of Na2SO4 in the presence of a carbon black. Mass spectrometry (MS) complements FTIR by being able to detect SO(g).

Red-orange, transparent single crystals of EuCN2 (Pnma (62), a = 1232.41(9), b = 395.26(3) and c = 539.43(4) pm, Z = 4) are obtained by the reaction of EuN, C and NaN3 in arc-welded Ta ampoules at 1300 K. The first ternary rare earth metal cyanamide is isotypic to α-SrCN2 and shows the characteristic frequencies for the CN22- unit in the optical spectra (νs = 1244; νas = 1969 and 2087; δ = 655/666 cm-1).

Theoretical and experimental Dalitz plots for three-body fragmentation of Na+ excited by He impact were studied. The fragmentation involves three adiabatic electronic states of Na3+ . Each of the three sectors of the Dalitz plots correspond to a different product adiabatic electronic state.

Molten salt mixtures containing sodium carbonate, sodium sulfide, and sodium sulfate have been electrolyzed to generate sodium oxide and sodium sulfide while removing carbon from the system in the form of gas and maintaining a sulfur balance in the melt. This investigation leads toward the development of an electrolysis-based recycle process for pulping chemicals. The molten salts are presently found in the chemical recovery process of kraft pulping. Electrolysis was performed in a divided melt/undivided atmosphere and divided melt/divided atmosphere to avoid consumption of the oxide and sulfide products. The anodic reaction was carbonate oxidation to carbon dioxide and oxygen while sulfide oxidation to polysulfides occurred to a lesser extent at less positive potentials; sulfate oxidation was not observed to occur. The cathodic reaction was sulfate reduction to sulfide and oxide, the desired molten precursors for recycled pulping liquors.

This invention pertains to a process for making α-methylenelactones and α-substituted hydrocarbylidene lactones. More specifically, the present invention obtains high yields of α-methylene-γ-butyrolactone by heating γ-butyrolactone and diethyl oxalate in the presence of a base. The second step comprises treatment of the α-oxalyl enolate salt with formaldehyde to afford the α-methylene-γ-butyrolactone.

Recent evidence has shown that the mesospheric sodium nightglow, a chemiluminescent process which produces atomic sodium D-line radiation in the Earth's upper atmosphere, proceeds through the first excited (A 2∑+) electronic state of NaO. The rate of D-line radiation production is proportional to the rate constant for the reaction of NaO(A 2∑+) + O(3P) and its branching ratio to produce excited Na(2P) rather than ground-state Na(2S). The only previously published measurement of the NaO + O(3P) reaction rate and branching ratio was performed under slow flow conditions and almost certainly primarily represents the reaction of groundstate NaO (X 2∏). We present low-pressure measurements of the NaO + O reaction kinetics using an NaO source reaction known to produce NaO in the (A 2∑+) state and determine the 290 K reaction rate constant to be (5.1 ± 1.8) × 10-10 cm3 s-1 and the branching ratio to produce Na(2P) to be 0.14 0.04. New data on the termolecular rate coefficient for the reaction Na + O2 + He → NaO2 + He at 290 K are also presented.

The reaction between Na and multilayer water on MgO(100)/Mo(100) has been studied by metastable impact electron spectroscopy (MIES), ultraviolet photoelectron spectroscopy (UPS), and temperature-programmed desorption (TPD). A water multilayer was exposed to Na at 100 K. During exposure, an attenuation of the surface water concentration concomitant with the formation of surface hydroxyls and metallic Na clusters is observed. After an anneal to 155 K, the metallic Na clusters disappear and the surface hydroxyls are essentially removed from the outermost surface, leaving water as the dominant surface species. Further annealing to >170 K leads to massive water and NaOH desorption, as indicated by TPD. After desorption of all multilayer components the species stabilized at the surface is primarily hydrated NaOH, which is stable up to 530 K.

The fragmentation of an Na3+ cluster following a collision with a fast He atom was theoretically studied. Trajectory results indicate that very different mechanisms contribute to the fragmentation process even in the simplest pathway when the cluster always stays in the ground electronic state and fragments adiabatically. The results are explained in terms of the binary, diatom, sequential, and complex mechanisms.

The specific kinetic features of a class of fast gas-phase reactions of the direct displacement of atoms from valence-saturated polyatomic molecules interacting with an atomic reactant discovered by the author are considered. An EPR-based technique for studying the kinetics of reactions of free atoms and radicals is described, which makes it possible to consider the role of longitudinal diffusion under flow conditions and requires no knowledge of absolute concentrations of the atomic reactant. For a wide temperature range, the experimental rate constants for abstraction and displacement reactions between free deuterium atoms and various types of hydrogen-containing compounds and reactions of hydrogen atoms with a number of hydrocarbons are reported. The kinetic isotope effect of the heterogeneous recombination of hydrogen and deuterium atoms on quartz is studied. It is suggested that reactions of atom displacement from molecules should be considered when studying mechanisms of complex processes with the use of isotopes.

The quantitative synthesis of four silicon and germanium compounds with the clathrate-II structure, Cs8Na16Si136 (1), Cs8Na16Ge136 (2), Rb8Na16Si136 (3), and Rb8Na16Ge36 (4), and their characterizations are reported. The corresponding Si-Si and Ge-Ge distances are determined with high accuracy from extensive single-crystal X-ray diffraction work. The compounds (cubic, space group Fd3m, a=14.7560(4), 15.4805(6), 14.7400(4), and 15.4858(6) A for 1, 2, 3, and 4, respectively) are stoichiometric, metallic, and remarkably stable. No evidence was found for vacancies in the silicon and germanium networks or partial occupancies of the alkali metal sites. The stoichiometry of these completely filled clathrates is consistent with the measured temperature-independent Pauli paramagnetism (χ = 7.2 x 10-4, 6.5 x 10-4, 6.9 x 10-5, and 1.4 x 10-4 emu/mol for 1, 2, 3, and 4, respectively) and metallic resistivity (ρ293 ? 10-5 Ω-cm). (C) 2000 Academic Press.

About 10 years ago, sodium aluminate has been found as suitable catalyst for the pure dehydrogenation of methanol to anhydrous formaldehyde. At first, the reaction was supposed to follow a heterogeneous mechanism. Later on, experimental results with a special set-up were at variance. Recent investigations revealed the loss of catalytically active species from the solid aluminate into the vapour phase where the entire reaction is likely to take place. Furthermore, evaporated elemental sodium catalyses the dehydrogenation of methanol in a homogeneous vapour-phase reaction. With respect to additional investigations carried out lately, a conclusive reaction mechanism is proposed which explains both the reaction with sodium aluminate and evaporated elemental sodium as catalysts in a proper way.

The present invention relates to sulfated polyhydroxy compounds used as anionic surfactants and to processes for their manufacture.

Novel 3-(substituted)-3-methyl-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylate, 4,4-dioxides which are of value for use in combination with beta-lactam antibiotics to increase the effectiveness of the antibiotics

Cs5[Na{W4N10}] was prepared from a mixture of NaNH2, CsNH2 and tungsten powder (molar ratio 1:10:4) at 700°C in autoclaves. After the reaction is finished the nitride is embedded in an alkali metal matrix. Dark red crystals were isolated by washing out the alkali metal with liquid ammonia at room temperature. The structure of Cs5[Na{W4N10}] was solved by X-ray single crystal data: I41 (No. 80), Z = 4, a = 13.926(3) A, c = 8.723(3) A, Z(Fo2) ≥ 3σ(Fo2) = 1535, Z(Variables) = 63, R/Rw = 0.040/0.052. The compound is highly sensitive against moisture giving oxotungstates and ammonia. It contains a framework of tetrahedra ∞3[WNN3/21.5-]. Sodium shares four terminal nitrogen ligands. Including sodium a distorted, β-cristobalite type arrangement ∞3[Na{W4N10}5-] results. It contains caesium in all interstices formed by twelve nitrogen ligands in so-called Friauf polyhedra. Johann Ambrosius Barth 1996.

A compound of the formula STR1 wherein R1 is an aliphatic hydrocarbon of 1 to 8 carbon atoms, R2 and R3 are individually hydrogen or alkyl of 1 to 4 carbon atoms, G is a hydrocarbon of 1 to 18 carbon atoms optionally containing at least one heteroatom and linked to the steroid nucleus by a carbon atom, X is XA or XB, XA is selected from the group consisting of hydrogen, alkyl of 1 to 8 carbon atoms, aralkyl of 7 to 15 carbon atoms, acyl of an organic carboxylic acid of 1 to 8 carbon atoms and Y is -B-O--CO--A-Z, B is a saturated or unsaturated, linear or branched alkylene of 1 to 8 carbon atoms, A is a saturated or unsaturated, linear or branched alkylene of 1 to 6 carbon atoms and optionally interrupted or ended by a bivalent aromatic or is a bivalent aromatic and Z is --COOH or --SO3 H which may be salified with an alkali metal, alkaline earth metal, an organic amine or --NH4 or XB is --COAZ, A and Z are defined as above and Y is selected from the group consisting of --C C--R4, --CH=CH--R4 and --CH2 --CH2 --R4, R4 is selected from the group consisting of hydrogen, halogen, alkyl of 1 to 6 carbon atoms, trialkylsilyl having 3 to 12 carbon atoms and phenyl, the alkyl and phenyl being optionally substituted and the 13-wavy line indicates that R1 can be in the α- or β-position having antiprogestomimetic and antiglucocorticoid properties among others.

The total sublimation pressure of Na2O(c) has been measured in the range 1000-1050 K by the torsion-effusion method, and the mass spectra of vapors over Na2O(c) and Na2O2(c) have been examined in order to resolve several issues regarding the thermochemical stability of the superoxide molecule NaO2.Measured torsion-effusion pressures are completely consistent with the primary sublimation process Na2O(c) = 2Na(g) + 0.5 O2(g) and set an upper limit of 200 kJ mol-1 for the bond strength D0(Na-O2).The ionization efficiency curves of Na+ and O2+ in the mass spectrumof vapor over Na2O(c) show no evidence for fragmentation contributions from NaO2.In addition, the absence of a detectable Na+/NaO2 fragment ion signal in vapor over Na2O2(c) can be used to derive an even tighter upper bound of 180 kJ mol-1 for D0(Na-O2).These results are in conflict with various kinetic analyses yielding D0(Na-O2) values of 202 to 243 kJ mol-1, but are in accord with rigorous theoretical calculations giving values near 160 kJ mol-1.

A compound selected from the group consisting of a compound of the formula STR1 wherein the dotted lines represent a possible endo or exo double bond, R1 and R2 are individually selected from the group consisting of hydrogen, alkyl of 1 to 8 carbon atoms, alkenyl and alkynyl of 2 to 8 carbon atoms, aryl of 6 to 14 carbon atoms, aralkyl of 7 to 18 carbon atoms and STR2 R'2 is alkyl of 1 to 8 carbon atoms or aryl of 6 to 14 carbon atoms, X is --O-- or --NR--, R is selected from the group consisting of hydrogen STR3 and --COOR', R' is hydrogen or alkyl of 1 to 8 carbon atoms, Y is selected from the group consisting of hydrogen, alkyl of 1 to 8 carbon atoms and alkenyl and alkynyl of 2 to 8 carbon atoms, all optionally substituted with at least one halogen or --OH, with the proviso that if Y is --OH, X is not --NH-- and their non-toxic, pharmaceutically acceptable addition salts of acids or bases having antibacterial and immunological properties.

A dithioacetal carbapenem of the formula STR1 in which R1 is hydrogen or C1-6 alkyl; n is 0, 1 or 2; R3 is hydrogen or C1-6 alkyl; R2 is C1-6 alkyl, phenyl optionally substituted with cyano, --CO2 NH2, --CH2 OH, --CH2 NH2, --CONHNH2 or with up to 5 halogen atoms, C1-6 alkyl or C1-6 alkyloxy groups, phenylmethyl optionally substituted with up to 5 halogen atoms, C1-6 alkyl or C1-6 alkyloxy groups on the phenyl ring, or a radical represented by the formula in which p is 0 or 1; X is five-membered aromatic heterocyclic ring containing up to 1 sulfur, 1 oxygen or 4 nitrogen atoms, optionally substituted with a C1-6 alkyl group, or six-membered aromatic heterocylic ring containing up to 4 nitrogen atoms, optionally substituted with a C1-6 alkyl group. or a non-toxic pharmaceutically acceptable salt, physiologically hydrolyzable ester or solvate thereof.

In connection with modeling of the chemistry of meteor-deposited sodium in the upper atmosphere, we have examined the mass spectra of severeal sodium-containing effusion sources for the evidence of gaseous NaHCO3, Na2CO3, or any other Na-C-O-H species.Alt

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The present invention relates to antitumor 4?-demethyl-epipodophyllotoxin glucosides having phosphate or sulfonate substituents on the sugar portion of the molecule.

Certain bicyclo [2.2.1] heptane and bicyclo [2.2.2] octane substituted tetrahydro-2H-pyran-2-ones and the corresponding ring-opened acids derived therefrom are potent inhibitors of the enzyme 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reduct

The production of titanium nitride, TiN, whiskers by reaction of sodium titanium bronze, NaxTiO2 (STB), with excess sodium cyanide, NaCN, at 1000°C is reported. The solubility of Ti from a STB in molten NaCN has been estimated experimentally. The TiN whiskers obtained under different experimental conditions have been examined by scanning electron microscopy and analyzed by analytical electron microscopy.

The unimolecular dissociation of metastable photoionized mass-selected heterogeneous alkali clusters is investigated using a tandem time-of-flight spectrometer.NaK+n and NanK+ are found to dissociate by evaporation of either a single neutral atom or a neutral dimer of the most abundant constituant.This behavior differs from the evaporation of heterogeneous neutral clusters which might always evaporate potassium in order to explain the sodium enrichment in the NaxKy neutral cluster distributions.This difference in the dissociation patterns of neutral and ionic heterogeneous clusters puts into evidence the influence of the charge in unimolecular dissociation processes.

Based on the carbon meter, a new technique has been developed for measuring the carbon potential of the structural materials as well as metal carbides. Some of these results are also briefly discussed in view of their importance in the transport of carbon in sodium-steel systems. Similarly, the hydrogen meter was used to investigate the Na-O-H system, which becomes important in the event of any water ingress into the sodium loops of fast reactors.

Metallic grey Li//3NaSi//6 is formed by heating the elements in stoichiometric amounts. The compound is the only stable ternary phase in the Li-Na-Si system, and does not belong to the tetrasilatetrahedrane derivatives. The novel complex layer structure is characterized by two-dimensional infinite polyanions showing polymerized tube-like structural units which are known from Hittorf's violet phosphorus and GeAs//2 respectively. The alkali metal atoms are inserted between the respective polyanionic layers Li//3NaSi//6 is a diamagnetic semiconductor with a molar susceptibility chi //m//o//l of minus 243 multiplied by 10** minus **6 emu mol** minus **1, R(300 K) equals 50 OMEGA and R(2 K) equals 3 multiplied by 10**3 OMEGA . Li//3NaSi//6 reacts with protic solvents as well as with benzophenone (in tetrahydrofuran) topotactically yielding a new metastable silicon modification, namely allo-Si.

When a chemical bond is broken in a direct dissociation reaction, the process is so rapid that it has generally been considered instantaneous and therefore unobservable.But the fragments formed interact with one another for times on the order of 10-13 s after the photon has been absorbed.On this time scale the system passes through intermediate transition configurations; the totality of such configurations have been, in the recent literature, designated as transition states. Femtosecond transition-state spectroscopy ( FTS ) is a real-time technique for probing chemical reactions.It allows the direct observation of a molecule in the process of falling apart or in the process of formation.In this paper, the first in a series on femtosecond real-time probing of reactions, we examine the technique in detail.The concept of FTS is explored, and the interrelationship between the dynamics of chemical reactions and molecular potential energy surfaces is considered.The experimental method, which requires the generation of spectrally tunable femtosecond optical pulses, is detailed.Illustrative results from FTS experiments for several elementary reactions are presented, and we describe methods for relating these results to the potential energy surface(s).

The present invention relates to a stereo-selective synthesis of leukotriene antagonists. More particularly, this invention relates to the stereo-selective synthesis of (βS,γR) and (βR,γS)--4-((3-(4-acetyl-3-hydroxy-2-propyl(phenoxy)propyl)-thio)-γ-hydroxy-β-methylbenzenebutanoic acid, and related compounds. These compounds are useful therapeutic agents for treating allergic conditions, asthma, cardiovascular disorders, inflammation and pain in mammals, especially humans. The compounds are also useful for inducing cytoprotection in mammals, especially humans.

Absolute photodissociation cross sections for gas phase NaCl are measured over the wavelength range of 189.7-359.8 nm at 300 K.Two well-resolved peaks are observed at 235 and 260 nm.The cross section also rises below 210 nm.These results are in good quali

A fast flow reactor, with an oven source and resonant fluorescence detection, was used to study the kinetics of Na atoms in the gas phase.The rate constant for Na + O3 is (7.3+/-1.4)X10-10 cm3 molecule-1 s-1 at 286 K and NaO + O2 is the predominant product channel.The rate constant for Na + N2O over the temperature range 240 to 429 K is (3.7+/-0.9)X10-10exp cm3 molecule-1 s-1.The kinetics of the NaO radical were measured directly.NaO is made in the flow tube by the reaction Na + N2O -> NaO + N2 with N2O in large excess.NaO is detected by conversion to Na atoms in the detection region by NaO + NO -> Na + NO2.NaO + O3 has two exothermic product channels, Na + 2O2 and NaO2 + O2.The rate constants are ca. 5X10-11 and (1.8+/-0.4)X10-10 cm3 molecule-1 s-1 at 296 K, respectively.Upper limits for NaO + N2O -> Na + N2 + O2 and NaO + N2O -> NaO2 + N2 are 1X10-16 and 2X10-15 cm3 molecule-1 s-1, respectively.The rate constant for NaO + NO -> Na + NO2 is ca. 1.5X10-10 cm3 molecule-1 s-1.Since wall collisions remove Na0 with near unit efficiency, Na0 diffusion coefficients can be measured.DNaO,He = 640+/-340 cm2 Torr s-1 and DNaO,N2O = 48+/-24 cm2 Torr s-1 at 295 K.The error limits in all cases represent the 95percent confidence level, including an estimate of systematic errors.

Shock-induced dissociation and the subsequent chemical relaxation processes of diatomic alkali halide molecules have been studied by time-resolved absorption spectrometry of alkali atoms, halide ions, and alkali halide molecules.The salts studied in detai

Kinetic data for the electroreduction of alkali metal cations in dimethylformamide and acetonitrile are reported at a variety of indium amalgam electrodes and at a gallium-indium electrode (eutectic composition).The kinetic parameters were found to depend markedly on the nature of the electrode material in which the product alkali metal is soluble.The data are discussed on the basis of a model in which adsorption of metal cation on the electrode and transfer of the cation from the solution phase to the metal phase are assumed to be the rate-controlling steps.This model provides an excellent description of the variation in the kinetic parparameters with electrode composition and potential.