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201 - 225 of 338
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CreatorTitleDescriptionSubjectDate
201 Wight, Charles AlbertThermal dissociation kinetics of solid and liquid ammonium nitrateThermogravimetry has been used to study the kinetics of the thermal dissociation of solid and liquid ammonium nitrate. Model-fitting and model-free kinetic methods have been applied to the sets of isothermal and nonisothermal measurements to derive kinetic characteristics of the processes. The appli...Thermal dissociation kinetics2001
202 Stang, Peter J.One-dimensional coordination polymers based on first-row transition metals: a solid-state study of weak backbone interactionsWe present further data on the solid-state structures of one-dimensional coordination polymers based upon dipositive transition metal hexafluoroacetylacetonate (hfacac) complexes. A variety of linking subunits are employed in order to investigate and probe the relatively weak interactions that make...Hexafluoroacetylacetonate complexes; Coordination polymers2001
203 Miller, Joel Steven; Epstein, Arthur J.Dynamic spin fluctuations in the molecular ferromagnet (DMeFc)(TCNE)The static and dynamic magnetic properties of the molecular ferromagnet decamethylferrocenium tetracyanoethenide (DMeFc)(TCNE) are studied via the muon-spin-relaxation technique. Spontaneous order is observed in the ferromagnetic ground state below 5 K, while the muon-spin-relaxation rate in the par...Magnetic; Magnetization; Paramagnetic2001
204 Voth, Gregory AlanFurther developments in the local-orbital density-functional-theory tight-binding methodQuantum-mechanical methods have become increasingly reliable as a complementary tool to experimental research. A variety of methods exist ranging in complexity from semiempirical methods to density-functional-theory (DFT) methods [using either the local-density approximation (LDA) or the generalize...Sankey-Niklewaki method; Fireball method; Pseudopotential; Exchange-correlation interactions; Gallium nitride; H20 dimer; Copper; gas-phase HMX2001-10
205 Armentrout, Peter B.Reactions of Pt+ with H2, D2, and HD: effect of lanthanide contraction on reactivity and thermochemistryA guided ion beam tandem mass spectrometer is used to examine the kinetic energy dependence of reactions of the third-row transition metal cation, Pt1, with molecular hydrogen and its isotopologs. A flow tube ion source produces Pt1 ions in its electronic ground state term and primarily in the lowes...Metal clusters; Platinum ions; Lanthanide contraction; Bond energies; Endothermic reactions; Transition metal ions; Dihydrogen2002
206 Morse, Michael DavidRotationally resolved spectra of Pt?High-resolution laser-induced fluorescence spectroscopy has been used to investigate the 18 163 cm21 band of Pt2 in a supersonically cooled molecular beam. Rotational constants of the ground and excited states were extracted from the rotationally resolved spectrum and determined to be B0'=0.031 754(...2002
207 Miller, Joel Steven; Epstein, Arthur J.Photoinduced magnetization in the organic-based magnet Mn(TCNE)x.y(CH2Cl2)Photoinduced magnetization in a magnet based on organic species is reported for the first time. Upon optical excitation in the blue region of spectrum, Mn (tetracyanoethylene)x .y(CH2Cl2) (x=2,y-0.8) exhibits increased magnetic susceptibility at temperatures as high as 75 K, accompanied with photo-i...Absorption; Magnetic; Infrared2002
208 Miller, Joel StevenNovel coordination of dicyanamide, [N(CN)2]-: preferential binding of the amide nitrogenCoII[N(CN)2]2(H2BiIm)2, 1, and {CoII[N(CN)2](H- 2BiIm)2}Cl, 2 (H2BiIm = 2,2'-biimidazole) have been structurally, spectroscopically, and magnetically characterized with both containing dicyanamides bound in unprecedented manners; namely, solely via the amide nitrogen for 1, and via an imide N form...Magnetic; Dicyanamide; Electron2002
209 Miller, Joel Steven; Epstein, Arthur J.Optical control of magnetic order in molecule-based magnet Mn(TCNE)x.y(CH2Cl2)Studies of photoinduced magnetization and photoinduced absorption in molecule-based magnet Mn(TCNE)x•y(CH2Cl2) (x=2, y-0.8, TCNE=tetracyanoethylene) are reported. Optical excitation in the blue region of spectrum leads to increased magnetization, accompanied by changes in the electronic spectrum...Spectrum; Absorption; Illumination2002
210 Armentrout, Peter B.Reactions of Ta+ and W+ with H2, D2, and HD: effect of lanthanide contraction and spin-orbit interactions on reactivity and thermochemistryA guided ion beam tandem mass spectrometer is used to examine the kinetic energy dependence of reactions of the third-row transition metal cations, Ta1, and W1, with molecular hydrogen and its isotopologs. A flow tube ion source produces Ta1 and W1 ions in their electronic ground state term and p...Metal clusters; Tantalum ions; Tungsten ions; Lanthanide contraction; Bond energies; Endothermic reactions; Transition metal ions; Dihydrogen2002
211 Miller, Joel Steven1H NMR investigation of the magnetic spin configuration in the molecule-based ferrimagnet [MnTFPP][TCNE]1H NMR line-shape measurements have been performed in the linear chain molecule-based ferrimagnet [MnTFPP][TCNE].xPhMe (TFPP=tetrakis(4-fluorophenyl)porphinato; TCNE=tetracyanoethylene) as a function of temperature. Hyperfine shifts of opposite sign were observed indicating the presence of two oppo...Magnetization; Magnets; Paramagnetic2002
212 Morse, Michael DavidResonant two-photon ionization spectroscopy of NiCA spectroscopic investigation of jet-cooled diatomic NiC has revealed a complex pattern of vibronic levels in the wave number range from 21 700 to 27 000 cm-1. Of the more than 50 vibronic bands observed, 31 have been rotationally resolved and analyzed. All are ?'=0+??"=0+ transitions, consistent wi...2002
213 Miller, Joel StevenOn the existence of long C-C bonds between pairs of anions which repel: when and why? A test case on the [TCNE]22- dimers found in ionic crystals*Many of the Cm[TCNE]n (C = cation) salts have intradimer C-C interactions in the range of 2.9 to 3.5 A(°) and show the electronic fingerprints associated with C-C bond formation (IR and UV spectra, magnetic properties, structural changes), despite the fact that two [TCNE].- anions should repel each...Electron; Spectroscopic; Salts2002
214 Armentrout, Peter B.Guided ion beam studies of the reactions of Vn+ (n = 2-13) with D2: cluster-deuteride bond energies as a chemical probe of cluster electronic structureThe kinetic energy dependencies of the reactions of Vn+ (n=2 - 13) with D2 are studied in a guided ion beam tandem mass spectrometer. Products observed are VnD1 for all clusters and VnD2 + for n=4 - 13. All reactions are observed to exhibit thresholds, except for formation of VnD2 + for n =4,5,7,9,1...Metal clusters; Vanadium ions; Bond energies; Endothermic reactions; Collision-induced dissociation; Transition metal ions; Deuterides2002
215 Morse, Michael DavidOptical spectroscopy of tungsten carbide (WC)Resonant two-photon ionization spectroscopy has been used to study the diatomic transition-metal carbide, WC. A low-resolution scan revealed a five-member vibrational progression beginning with the 0-0 band at 17 585 cm-1. Analysis of this progression yielded a vibrational frequency of ?'e8(184W12C)...2002
216 Miller, Joel StevenIsolation of two salts from the reduction of TCNE with [(n-C3H7)4N]I. A further example of long 2.87 Ã pi-C-C bonding in pi-[TCNE]22-Reduction of tetracyanoethylene, TCNE, with tetrakis(n-propyl)ammonium iodide, [Pr4N]I, results in a new example of long pi*-CC bonded pi-[TCNE]22- dimers with a 2.870(4) A(°) intradimer CC bond, which is structurally and spectroscopically characterized. This reaction also results in isolation of ...Synthesis; Intradimer; Crystals2002
217 Armentrout, Peter B.Thermochemistry of small cationic iron-sulfur clustersThe kinetic energy dependences of the reactions of Fen 1 with COS (n=2-6) and CS2 (n=2-5) are studied in a guided-ion beam tandem mass-spectrometer. The main products arise from sulfur transfer and subsequent losses of Fe atoms. In the case of CS2 , this reactant also formally replaces one Fe atom ...Iron-sulfur clusters; Endothermic reactions; Bond energy2002
218 Armentrout, Peter B.Reactions of Ta+, W+, and Pt+ with H2, D2, and HD: effect of lanthanide contraction and spin-orbit interactions on reactivity and thermochemistryThere have been extensive experimental studies of the reactions of atomic first-row and second-row transition metal cations with dihydrogen and its isotopic analogues in our group. For third-row transition metal cations, however, only La+ and Lu+ systems have been studied experimentally although t...Lanthanide contraction; Spin-Orbit interactions; Reactivity2002
219 Miller, Joel StevenCharge transfer complexes of 2,4,6-tricyano-s-triazine with tetrathiafulvalene (TTF) and N,N,N' ,N'-tetramethyl-p-phenylenediamine (TMPD)Reaction of 2,4,6-tricyano-s-triazine (TCT) with tetrathiafulvalene (TTF) and N,N,N',N'-tetramethylp-phenylenediamine (TMPD) leads to 1 : 1 charge transfer complexes. The crystal structures of the TTF[TCT], as well as the decomposition product due to hydrolysis of the [TMPD][TCT], i.e. HTMPD]+[2,4-d...Electron; Solution; Hydrolysis2002
220 Miller, Joel StevenInnovation in crystal engineeringThe first CrystEngComm discussion meeting on crystal engineering has demonstrated that the field has reached maturity in some areas (for example: design strategies, characterization of solid compounds, topological analysis of weak and strong non-covalent interactions), while the quest for novel pro...Research; Design; Molecular2002
221 Wight, Charles AlbertThermal activation of the high explosive NTO: sublimation, decomposition, and autocatalysisThermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) show that the heating of 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (NTO) leads to competitive sublimation and condensed-phase exothermic decomposition. Model-free isoconversional analysis has determined activation energies...NTO; Thermal activation; Differential scanning calorimetry; Exothermic decomposition; Competitive sublimation2002
222 Wight, Charles AlbertThermal decomposition of a melt-castable high explosive: isoconversional analysis of TNAZThe thermal decomposition kinetics of the high explosive 1,3,3-trinitroazetidine (TNAZ) have been measured by nonisothermal differential scanning calorimetry (DSC). Samples of TNAZ in open pans and pierced pans undergo mainly melting (?Hfus = 27 ± 3 kJ mol-1) and vaporization (?Hvap = 74 ± 10 kJ m...Thermal decomposition; Melt-castable high explosive; TNAZ; Nonisothermal differential scanning calorimetry; Exothermic decomposition2002
223 Miller, Joel Steven; Epstein, Arthur J.Viscous behavior in a quasi-1D fractal cluster glassThe spin glass transition of a quasi-1D organic-based magnet ([MnTPP][TCNE]) is explored using both ac and dc measurements. A scaling analysis of the ac susceptibility shows a spin glass transition near 4 K, with a viscous decay of the thermoremanent magnetization recorded above 4 K.We propose an ex...Transition; Magnet; Magnetization2002
224 Armentrout, Peter B.Guided ion beam studies of the reaction of Nin+ (n=2-16) with D2: nickel cluster-deuteride bond energiesThe kinetic-energy dependences of the reactions of Nin+ (n=2-16) with D2 are studied in a guided ion beam tandem mass spectrometer. The products observed are NinD+ for all clusters and NinD2 + for n=5-16. Reactions for formation of NinD+ are observed to exhibit thresholds, whereas cross sections for...Metal clusters; Nickel ions; Bond energies; Deuterides; Collision-induced dissociation; Endothermic reactions2002
225 Armentrout, Peter B.Thermodynamics of ammonia activation by iron cluster cations: guided ion beam studies of the reactions of Fen+ (n=2-10,14) with ND3The kinetic energy dependences of the reactions of Fen 1 (n52 - 10,14) with ND3 are studied in a guided ion beam tandem mass spectrometer over the energy range of 0-10 eV. Dehydrogenation of ammonia to form FenND1 is found to be efficient and exothermic for n54 in agreement with previous FT-ICR stu...2003
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