- Mode specific internal and direct rotational predissociation in HeHF, HeDF, and HeHCl: van der Waals complexes in the weak binding limit
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The near-infrared vibration-rotation spectra of the weakly bound complexes HeHF, HeDF, and HeHCl are observed in a slit supersonic expansion.The spectra correspond to simultaneous excitation of vibration and internal rotation of the H(D)X subunit within the complex.The HeHF and HeDF P/R branch transitions show J-dependent excess linewidths, which are attributed to rapid predissociation of the excited states from intramolecular rotation-translation energy transfer.The corresponding P/R branch transitions in HeHCl are not observed despite good S/N on the Q branch, suggesting even more rapid predissociation for the upper state of this complex.The Q branch transitions for all three complexes abruptly terminate at low J, yielding lower limits to the number of bound rotational states and good estimates of the dissociation energies D0 = 7.1 +/- 0.1 cm-1 for HeHF and HeDF, and 10.1 +/- 1.2 cm-1 for HeHCl.In addition to isotropic intermolecular potentials, the HeHF/HeDF data yield considerable information on the potential anisotropy in the region sampled by the bound and quasibound states.The information so obtained is complementary to results from scattering studies and provides sensitive tests for refining trial potential energy surfaces.
- Lovejoy, Christopher M.,Nesbitt, David J.
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- INFRARED SPECTRA OF DIATOMIC HALOGEN COMPLEXES WITH HYDROGEN FLUORIDE IN SOLID ARGON AND NEON
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Chlorine was condensed at 12 K with HF in excess argon, which produced two 1:1 complexes of the form HF-Cl2 and Cl2-HF on the basis of infrared spectra.Increasing the HF concentration favored secondary 1:2 complexes with both (HF)2-Cl2 and Cl2-(HF)2 arran
- Hunt, Rodney D.,Andrews, Lester
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- Infrared spectra of the very weak H2--HF and O2--HF complexes in solid neon
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Very weak, hydrogen bonded complexes of molecular hydrogen and oxygen with HF have been prepared by condensing the neon diluted reagents at 4-5 K.Infrared spectra of the H2-- HF complex revealed a νs (HF) mode at 3938 cm-1 and νc(H2) mode at 4155 cm-1 which are red shifted from isolated molecule values in agreement with theoretical predictions.Increasing the HF concentration produced a 1:2 complex, H2-(HF)2.Similar experimental results were obtained for molecular oxygen complexes using HF and DF; the oxygen fundamental in this complex, however, exhibited a 6 cm-1 blue shift.Spectra of these complexes in argon matrices showed that argon is not an effectively inert medium for very weak complexes where interaction with the solid argon environment is competitive with the H2-HF and O2-HF interactions.
- Hunt, Rodney D.,Andrews, Lester
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- H/D isotope exchange between methane and magic acid (HSO 3F-SbF5): An in situ NMR study
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The kinetics of hydron exchange between methane and a series of DSO 3F-SbF5 superacids were measured by in situ 2H decoupled 1H NMR spectroscopy. The rates of exchange showed a strong dependence on antimony pentafluoride concentration, with the free energy of activation ΔG# (30°C) decreasing from 97 to 84 kJ mol -1 over the range of concentration 19 to 49 mol % SbF5. The constant free enthalpy of activation ΔH# (ca. 65 kJ mol-1) and the decreasing entropy of activation ΔS# seem to indicate that an increase in acidity of the superacid system does not substantially change the nature of the transition state but rather acts on its solvation.
- Walspurger, Stephane,Goeppert, Alain,Haouas, Mohamed,Sommer, Jean
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- Infrared Spectra of Cyanogen Halide Complexes with Hydrogen Fluoride in Solid Argon
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Cyanogen chloride was condensed at 12 K with HF in excess argon, producing two 1:1 complexes of the form ClHN--HF (1) and HF--ClCN (2).Increasing the HF concentration produced a 1:2 complex, ClCN--(HF)2, while increasing the ClCN concentration produced a 2:1 complex, ClCN--HF--ClCN.The HF submolecule stretching frequency for the major primary 1:1 complex (1) was observed at 3597 cm-1, and a single HF liberational mode appeared at 602 cm-1.These fundamentals are comparable to the HF modes for alkyl cyanide complexes.In sharp contrast, the second 1:1 complex (2), which is similar to the HF--ClF and HF--Cl2 complexes, displayed a HF stretching frequency at 3912 cm-1.Similarresults were obtained for cyanogen bromide and cyanogen iodide complexes with hydrogen fluoride and deuterium fluoride.In addition, the photolysis of hydrogen cyanide and fluorine produced the complex FCN--HF with no evidence for a complex analogous to 2.The HF stretching and liberational modes for this complex were observed at 3662 and 553 cm-1, respectively.Similarly, the reaction between cyanogen and HF formed only the NCCN--HF complex.The HF modes for this complex were observed at 3757 and 460 cm-1, which indicate a weaker interaction than found for the cyanogen halides and HF.
- Hunt, Rodney D.,Andrews, Lester
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- XeOF2, F2OXeN≡CCH3, and XeOF 2·nHF: Rare examples of Xe(IV) oxide fluorides
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The syntheses of XeOF2, F2OXeN≡CCH3, and XeOF2·nHF and their structural characterizations are described in this study. All three compounds are explosive at temperatures approaching 0 °C. Although XeOF2 had been previously reported, it had not been isolated as a pure compound. Xenon oxide difluoride has now been characterized in CH3CN solution by 19F, 17O, and 129Xe NMR spectroscopy. The solid-state Raman spectra of XeOF2, F2OXeN≡CCH3, and XeOF 2-nHF have been assigned with the aid of 16O/ 18O and 1H/2H enrichment studies and electronic structure calculations. In the solid state, the structure of XeOF2 is a weakly associated, planar monomer, ruling out previous speculation that it may possess a polymeric chain structure. The geometry of XeOF2 is consistent with a trigonal bipyramidal, AX2YE2, VSEPR arrangement that gives rise to a T-shaped geometry in which the two free valence electron lone pairs and Xe-O bond domain occupy the trigonal plane and the Xe-F bond domains are trans to one another and perpendicular to the trigonal plane. Quantum mechanical calculations and the Raman spectra of XeOF 2·nHF indicate that the structure likely contains a single HF molecule that is H-bonded to oxygen and also weakly F-coordinated to xenon. The low-temperature (-173 °C) X-ray crystal structure of F 2OXeN≡CCH3 reveals a long Xe-N bond trans to the Xe-O bond and a geometrical arrangement about xenon in which the atoms directly bonded to xenon are coplanar and CH3C≡N acts as a fourth ligand in the equatorial plane. The two fluorine atoms are displaced away from the oxygen atom toward the Xe-N bond. The structure contains two sets of crystallographically distinct F2OXeN≡CCH3 molecules in which the bent Xe-N-C moiety lies either in or out of the XeOF2 plane. The geometry about xenon is consistent with an AX2YZE 2 VSEPR arrangement of bond pairs and electron lone pairs and represents a rare example of a Xe(IV)-N bond.
- Brock, David S.,Bilir, Vural,Mercier, Helene P. A.,Schrobilgen, Gary J.
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- Infrared spectra of HF complexes with methane, silane, and germane
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HF complexes with methane, silane, and germane were prepared in nobIe gas matrices and studied using infrared spectroscopy and Hartree-Fock (SCF) calculations.The spectra indicate that two types of 1:1 complexes were formed, a normal one in which the hydrogen of HF is interacting with one hydrogen of silane or germane, and a reverse complex in which the fluorine of HF is interacting with one hydrogen atom of methane.The IR inactive symmetric C-H stretch in CH4 was observed in the CH4--FH complex as a weak band at 2914 cm-1.In the silane--HF and germane--HF complexes, the Si-H and Ge-H stretches were perturbed approximately 50 cm-1 to higher energy relative to the antisymmetric stretch ν3 in each parent molecule, but the ν1, modes were masked by the strong ν3 parent bands.Higher order 1:2 (AH4:HF) complexes were also observed and support the normal or reverse-type geometry of the 1:1 complexes.
- Davis, Steven R.,Andrews, Lester
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- OPERATING CHARACTERISTICS OF A TRANSVERSE-FLOW DF- CO2 PURELY CHEMICAL LASER
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Experimental results are presented giving the operating characteristics of a newly developed DF-CO//2 purely chemical laser. The present oscillator is capable of a maximum cw output power of 162 w at 10. 6 U with no external energy source used to initiate or sustain laser excitation. An optical axis has been employed aligned transverse to the flow direction with a view toward achieving operation which can be directly scaled to high output powers. Measurements of saturation parameter, unsaturated gain coefficients,and vibration-rotation state populations for P- and R- branch CO//2 (001) to CO (100) transitions, power output, operating temperatures and pressures, and chemical efficiency are presented.
- COOL TA,SHIRLEY JA,STEPHENS RR
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- Slit jet infrared spectroscopy of hydrogen bonded N2HF isotopomers: Rotational Rydberg-Klein-Rees analysis and H/D dependent vibrational predissociation rates
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High resolution IR laser direct absorption spectra in a slit jet are presented and analyzed for nitrogen (15N14N-HF, 14N15N-HF, 15N15N-HF), and deuterium (14N14N-DF) substituted N2HF isotopomers.Both 14N15N-HF and 15N14N-HF isomers are observed, indicating a sufficiently deep minimum in the hydrogen bonding potential energy surface to quench internal rotation of the N2.The vibrationally averaged stretching potentials for each substituted species are recovered from rotational Rydberg-Klein-Rees (RKR) analysis.Features of the onedimensional (1D) potential surface such as hydrogen bond length (RH-bond), harmonic force constant (k?), and well depth (De) are then tested for isotopic invariance by direct comparison of the different isotopomers.Agreement among the various N substituted species for HF based complexes for either υHF = 0 or 1 is excellent, and provides effective 1D potentials for the stretching coordinate between 3.39 and 3.75 Angstroem.There is a 43 cm-1 (ca. 10percent) strengthening of the hydrogen bond upon HF vibrational excitation, as quantitatively reflected in the experimental redshifts and the shape of the RKR potentials for υHF = 0 and 1.The hydrogen bond is further strengthened by D/H isotopic substitution; this is a result of reduced vibrational averaging over DF vs HF bending motion, yielding a more linear, and hence stronger, hydrogen bond geometry.In contrast to the nearly apparatus-limited linewidths (Δνprediss ca 7 MHz) observed for each of the N2HF isotopomers, the N2DF complexes yield significantly broadened lines with 73 +/- 9 MHz homogeneous linewidths due to vibrational predissociation.This tenfold increase in predissociation rates upon deuteration is in contrast to previous measurements in other HF/DF containing complexes, and indicates the importance of a near resonant vibrational channel to form N2(υ = 1) + DF(υ = 0).The energetic accessibility of this V -> V channel would suggest an upper limit on the N2DF binding energy of D0 547 cm-1, which is also consistent with upper limits on D0 from the rotational RKR analysis.
- Nesbitt, David J.,Lindeman, Theodore G.,Farrell, John T.,Lovejoy, Chris M.
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- Deuterium labeling, FTIR, and ab initio investigation of the solution-phase thermal reactions of alcohols and alkenes with hydrogen-terminated silicon surfaces
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The reactions of alcohols and alkenes with hydrogen-terminated silicon surfaces have been investigated using infrared spectroscopy and deuterium labeling of the reagents and the surface termination. Transmission FTIR spectra were obtained on samples of electrochemically grown porous silicon or mechanically abraded silicon wafers to obtain a sufficient signal-to-noise ratio. The spectral assignments are supported by ab initio calculations on small molecule models at the MP2/6-311++G(d,p) level of theory. A convenient method for the preparation of fully deuterated (D-terminated) silicon wafers is reported; however, fully deuterated porous silicon could not be prepared this way. The spectrum of partially deuterated porous silicon could be assigned on the basis of the computed harmonic vibration frequencies for Q3Si-SiH2-SiQ3 and Q3Si-SiHD-SiQ3 where Q is a pseudo-hydrogen atom with the atomic mass of Si. The reaction of O-deuterated alcohols and water on porous silicon produced Si-D stretching and Si-HD scissor modes in the infrared spectrum. The kinetics were consistent with either a dissociative adsorption or an electrochemical corrosion mechanism for this reaction. However, in all cases a net decrease of Si-H/D species on the surface was observed. The magnitude of this decrease is consistent with hydrogen evolution from a hydridic reactivity of the surface termination analogous to the formation of SiO2 via hydrolysis of molecular hydrosilanes. The Si-H/D, OxSi-H, and Si-O vibrations could be assigned using small molecule models of the form QOSiH2SiQ3, QOSiH2OQ, and (QO)3SiH. Significant amounts of silicon alkoxide species are formed even in the presence of water, but the major process in wet solvents is hydrogen evolution and oxide formation. The currently accepted mechanism for the hydrosilylation of alkenes by hydrogen-terminated silicon surfaces involves the attack of a silyl radical on the double bond to produce a Si-C bond and a carbon-centered radical. In principle, this carbon radical may abstract a hydrogen atom from the surface and propagate a chain; however, using deuterated silicon wafers no C-D stretching vibrations could be detected. This indicates that under the conditions employed (1 M alkene solutions in refluxing toluene) the carbon radical abstracts a hydrogen atom from the solvent or another alkene molecule. Ab initio calculations on small molecule models were used to investigate theoretically the shift to low frequency in the Si-H vibrations on the formation of Si-C bonded species at the surface and this effect is attributed to the replacement of Si-H2 with C-Si-H functionality at the surface.
- Bateman,Eagling,Horrocks,Houlton
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- HF stretching-bending combination bands for small complexes in solid argon
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Infrared spectra of HF (with DF substitution) in solid argon contain weak HF stretching-bending combination bands for N2-HF, (HF)2, and (HF)3 that are higher than the sum of fundamentals. This is in accord with stronger hy
- Andrews, Lester,Souter, Philip F.
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- Infrared Spectra of Amide-HF Complexes in Solid Argon
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Hydrogen-bonded complexes of amides and hydrogen fluoride have been prepared in solid argon.FTIR spectra of these complexes compared to spectra of similar carbonyl and amine complexes show that HF is hydrogen bonded to the carbonyl oxygen in the primary i
- Bohn, Robert B.,Andrews, Lester
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- The protonation of dimethyl sulfoxide: Spectroscopic examinations of [(CX3)2SOX]+MF6- (X=H, D; M=As, Sb) and the X-Ray Structure of [(CH3)2SOH+]4Ge3F16 4-
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Dimethyl sulfoxide (DMSO) reacts with the superacidic solutions of XF/MF5 and XF/GeF4 (X=H, D; M=As, Sb) under formation of the corresponding salts [(CX3)2SOX+]MF6- and [(CH3)2SOH+]4Ge3F16 4-, respectively. The salts are characterized by vibrational and NMR spectroscopy, and in the case of [(CH3)2SOH+]4Ge3F16 4- also by single-crystal X-ray analysis. The salt [(CH3)2SOH+]4Ge3F16 4- crystallizes in the monoclinic space group P21/c with two formula units in the unit cell. The crystal structure possesses an unusual anion consisting of a chain of three slightly distorted fluorine-bridged GeF6 octahedra. The vibrational spectra are compared to the quantum chemically calculated free [(CX3)2SOX+] cations. The described salts are isolated examples of completely protonated DMSO molecules in the condensed phase.
- Hopfinger, Mathias,Lux, Karin,Kornath, Andreas
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- Reactions of formic acid methylester in the super acidic system XF/MF5 (X = H, D: M = As, Sb) and the crystal structure of HC(OH)(OCH3)+asf6-
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The reaction of formic acid methyl ester in the superacidic system XF/MF5 (X = H, D: M = As, Sb) leads to the hydroxy methoxy carbenium hexafluorometallates. The very hydrolysable and thermo labile salts are characterized by vibrational and NMR spectroscopic methods. Under inert conditions they are stable at -20°C for some weeks. HC(OCH3)(OH)+AsF6- crystallizes in the monoclinic space group P21/c (No. 14) with a = 5.275(1) A, b = 11.059(1) A, c = 12.113(1) A und β= 96.64(1)° and four formula units per cell.
- Minkwitz, Rolf,Neikes, Frank,Ruettershoff, Dirk
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- Synthesis of water-soluble hypervalent iodine reagents for fluoroalkylation of biological thiols
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New open-chain and water-soluble hypervalent iodine reagents were synthesized and used for the transfer of fluoroalkyl groups to sulfur atoms of cysteine and cysteine-containing peptides under biocompatible conditions. Some of the reagents displayed excellent reactivity despite their limited stability in aqueous media. In reactions with a short cysteine-containing peptide, in addition to the expected S-fluoroalkylated product, a range of side-products were obtained. The amount of side-products depended on the conditions used (type of reagent, concentration, and pH). With highly activated hypervalent iodine reagents, a new reactive mode was observed-reaction with disulfides to form fluoroalkyl thiols.
- Klimánková, Iveta,Hubálek, Martin,Matou?ek, Václav,Beier, Petr
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supporting information
p. 10097 - 10102
(2019/12/23)
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- The Existence of Tricyanomethane
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Calcium tricyanomethanide reacts with hydrogen fluoride under formation of tricyanomethane and Ca(HF2)2. Tricyanomethane is stable below -40 °C and was characterized by IR, Raman, and NMR spectroscopy. The vibrational spectra were compared to the quantum-chemical frequencies at the PBE1PBE/6-311G(3df,3dp) level of theory and confirm the predicted C3v symmetry of the molecule with regular C-H (109.8pm), C-C (146.7pm), and C-N (114.7pm) bonds.
- Soltner, Theresa,H?usler, Jonas,Kornath, Andreas J.
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supporting information
p. 13775 - 13776
(2015/11/11)
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- The rate constants of the two channels of the reaction of F atoms with HD in the temperature range 193-300 K
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The rate constants for the two channels of the reaction of F atoms with HD, kF + HD and kF + DH, have been determined in the temperature range 193-300 K. The sum of rate constants kF + HD + kF + DH was determined by a competitive method and a discharge-flow-mass spectrometric technique, using the F + D2 reaction as a reference reaction. By combining the results for this sum of rate constants with published results for the rate constant kF+D2 and for the ratio of rate constants kF + HD/kF + DH, values were derived for the individual rate constants kF + HD and kF + DH. The experimental results are compared with published results of quantum mechanical calculations and of quasiclassical calculations on the Stark-Werner potential energy surface.
- Persky, Avigdor
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p. 455 - 458
(2008/10/09)
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- Rovibrational and dynamical properties of the hydrogen bonded complex (CH2)2S-HF: A combined free jet, cell, and neon matrix-Fourier transform infrared study
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The infrared study of the rovibrational and dynamical properties of the hydrogen bonded complex (CH2)2S-HF dimer was analyzed. It was observed that the combination of controlled temperature effects over a range of 40-250 K and a sophisticated band contour simulation program allowed the separation of homogeneous and inhomogeneous contributions. It was also observed that with the strengthening of the hydrogen bond upon vibrational excitation of HF, the sign of the coupling constants remained consistent. It was found that effective linewidth provides a lower bound for the predissociation lifetime of 10 ps.
- Asselin,Goubet,Lewerenz,Soulard,Perchard
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p. 5241 - 5252
(2008/01/27)
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- Deuterium fluoride synthesis by deuterolysis of chlorine trifluoride
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An original method for the synthesis of anhydrous deuterium fluoride DF of high chemical and isotopic purity was developed and implemented. This method involves the controlled hydrolysis (deuterolysis) of chlorine trifluoride by 99.8% heavy water in an originally designed vacuum installation. One DF mole of 98.2% D isotopic purity was obtained in an about 90% yield based on D2O.
- Parbuzin,Sukhoverkhov,Yakovlev
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p. 1783 - 1784
(2008/10/08)
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- Deuterium fluoride synthesis in the system D2-AgF2-ClF3
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Two pathways to obtaining deuterium fluoride in the system D2-AgF2-ClF3 that exclude direct con-tact of D2 with ClF3 are investigated: (1) DF synthesis by the action of D2 on AgF2 and AgF2 regeneration by the action of ClF3 on Ag and (2) a three-stage synthesis simultaneously producing two deuterium halides (DF + DCl).The two-stage process is recommended as a convenient route to obtain DF of high chemical and isotopic (99% D) purity on a laboratory scale from commercially available reagents.
- Parbuzin,Sukhoverkhov,Yakovlev
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p. 1466 - 1468
(2008/10/08)
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- Isotope effects in the deactivation of O( 1 D) atoms by XCl and XF (X=H,D)
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The method of time-resolved laser magnetic resonance (LMR) was used to study the deactivation of O(1D) by HCl, DCl, HF, and DF at room temperature. For O(1D)+XF(X=H,D), the effect of deuteration on the rates of physical quenching and
- Chichinin
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p. 425 - 432
(2008/10/08)
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- Observation of a transition state resonance in the integral cross section of the F+HD reaction
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We have studied the reaction F+HD at low collision energies using a combination of experimental and theoretical methods. Clear evidence for a reactive resonance is found in the integral cross section for the reactive channel F+HD→HF+D. Using a crossed molecular beam apparatus, the total reactive cross sections for the HF+D and DF+H channels were obtained in the collision energy range of 0.2-5 kcal/mol. In addition, Doppler profiles were obtained over this range of energies, which provide information about the angularly resolved distribution of final vibrational states. The cross section shows a distinctive steplike feature near 0.5 kcal/mol. Furthermore, the Doppler profiles reveal a dramatic change in the angular distribution of products over a narrow energy range centered at 0.5 kcal/mol. This feature is shown to arise from a reactive resonance localized near the transition state. Theoretical scattering calculations have been carried out using the Stark-Werner potential energy surface, which accurately reproduce the shape of the resonance feature. A detailed analysis of quantum dynamics using the spectral quantization method reveals that a quantum resonance exists near 0.52 kcal/mol, which is localized about the collinear FHD geometry. At collision energies below 1 kcal/mol, the reaction was found to proceed almost exclusively through resonant tunneling with very little contribution from direct, over the barrier, reaction. The properties of the quantum resonance, such as the position, lifetime, and partial widths were found to correlate well with the experimental results and the quantum scattering calculations.
- Skodje, Rex T.,Skouteris, Dimitris,Manolopoulos, David E.,Lee, Shih-Huang,Dong, Feng,Liu, Kopin
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p. 4536 - 4552
(2007/10/03)
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- Kinetics of the reactions F + H2S and F + D2S at 298 K
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The rate constants for the reactions F + H2S and F + D2S at 298 K were determined by a competitive method using the reaction F + CH4 as a reference reaction. The ratios of rate constants kF + H2S/kF + CH4 and kF + D2S/kF + CH4 were determined by a discharge-flow-mass spectrometric technique. By combining the values for these ratios with the value for kF + CH4 at 298 K, the values kF + H2S = (1.46 ± 0.12) × 10-10 cm3 molecule-1 s-1 and kF + D2S = (1.42 ± 0.12) × 10-10 cm3 molecule-1 s-1 were obtained. The kinetic isotope effect kF + H2S/kF + D2S was determined directly and the value 1.04 ± 0.02 was obtained. The results of this study are compared with previous literature data.
- Persky, Avigdor
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p. 390 - 394
(2008/10/08)
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- An Experimental Study of the Reactions of OH Radicals with 1,3-Butadiyne, Propyne, 1-Butyne and 2-Butyne in the Gas Phase
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The reactions of OH/OD radicals with butadiyne, propyne, 1-butyne and 2-butyne have been studied at low temperature (295 K) in low pressure reactors (0.1-15 mbar).Samples were withdrawn continuously by a molecular beam device and analyzed by a mass spectrometer.The detection sensitivity was enhanced by modulation techniques and single ion counting.The primary reaction products are described mainly by an addition mechanism.For the reaction of butadiyne with OH radicals the mechanism and a rate constant of 1.2(+/-0.6)E13 cm3/mol s were found.The reactions of the adduct with the alkynes were found to be very fast.Complementary studies of the reactions of H/D + C4H2 and F + C4H2 are reported. - Keywords: Chemical kinetics / Elentary reactions / Mass spectrometry
- Bartels, M.,Heinemann-Fiedler, P.,Hoyermann, K.
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p. 189 - 208
(2007/10/02)
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- Kinetic and mechanistic investigations of F + H2O/D2O and F + H2/D2 over the temperature range 240-373 K
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The rate constants for the reactions of fluorine atoms with H2O and D2O have been determined over the temperature range 240-373 K by using a discharge flow system at 1-2 Torr of total pressure. F atoms were detected by chemical conversion with deuterium. The resulting D atoms were detected by atomic resonance scattering. The rate constants are k1 = (1.6 ± 0.3) × 10-11 exp[(-28 ± 42)/T] cm3 molecule-1 s-1 for F + H2O → HF + OH and k2 = (8.4 ± 1.2) × 10-12 exp[(-260 ± 110)/T] cm3 molecule-1 s-1 for F + D2O → DF + OD. The reported error limits are at the 95% confidence level. The reactions F + H2 → HF + H (k3 = (1.2 ± 0.1) × 10-10 exp[(-470 ± 30)/T] cm3 molecule-1 s-1) and F + D2 → DF + D (k4 = (9.3 ± 1.1) × 10-11 exp[(-680 ± 50)/T] cm3 molecule-1 s-1) were also studied over the same temperature range. The rate constants for the latter reactions are in excellent agreement with previous studies. The low activation energy and A factor for the F + H2O/D2O reactions, as well as the slightly enhanced kinetic isotope effect (3.9 at 298 K), suggest a tunneling mechanism for these reactions, and thus the mechanistic interpretation of this system requires some knowledge of the potential energy surface at the microscopic level. Ab initio calculations on this system predict a classical barrier height of approximately 10 kcal/mol, while a semiempirical BEBO calculation predicts a barrier height of a one-dimensional tunneling model. With use of the theoretical implications in conjunction with the experimental evidence, a potential energy surface has been calculated for this reaction that leads to better agreement with the experimental results. The best-fit prediction of the observed activation energy and kinetic isotope effect suggest that the mechanism for this reaction involves tunneling through a classical barrier height of approximately 4 kcal/mol.
- Stevens, Philip S.,Brune, William H.,Anderson, James G.
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p. 4068 - 4079
(2007/10/02)
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- Infrared Chemiluminescence Study of the F Atom + HMn(CO)5 Reaction
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The HF infrared chemiluminescence from the reaction of F atoms with HMn(CO)5 has been observed in a flow reactor.The nascent HF vibrational distribution is P1-P4=0.20:0.44:0.35:ca. 0.01, and v(HF)> is 0.31 for P0 assigned as zero.The HF(ν,J) populations do not extend to the thermochemical limit, and v(HF) is abnormally low relative to typical H abstraction reaction by F atoms.The H abstraction reaction from toluene-d5 was reinvestigated to provide a reference for a system yielding HF(ν) and a product with a large radical stabilization energy.The D0(CH3C6D4-D) was estimated as -1, based upon the highest observed DF(ν,J) level.
- Wategaonkar, S. J.,Setser, D. W.
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- REACTIONS OF FLUORINE ATOMS WITH NORMAL AND DEUTERATED METHANOLS.
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The reactions of fluorine atoms with normal and deuterated methanols have been studied at low pressure using a fast discharge flow reactor. Samples were withdrawn continuously via a molecular beam sampling system and were analyzed by a mass-spectrometer. The rate constants have been determined.
- Khatoon,Hoyermann
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p. 669 - 673
(2007/10/02)
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- INFRARED MATRIX ISOLATION STUDIES OF THE REACTIONS OF F2 WITH SULFUR AND PHOSPHORUS BASES
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The matrix isolation technique has been used to study the initial intermediate products of the reaction of molecular fluorine, F2, with several alkyl sulfides, as well as with trimethylphosphine.While previous studies of the reaction of these bases with ClF and Cl2 demonstrated that charge transfer complexes are formed, no evidence has been observed here for complex formation.Rather direct reaction occurs for each system studied, leading in several cases to hydrogen displacement products, while in other systems the spectral evidence supports a direct addition reaction.For example, in the F2/H2S system, initial formation of H2SF2 is postulated, followed by HF elimination to form HSF upon Hg arc irradiation.
- Machara, Nicholas P.,Ault, Bruce S.
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p. 129 - 138
(2007/10/02)
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- Infrared spectra and UHF SCF calculations of HF complexes with NO, (NO)2, and NO2
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HF complexes with nitric oxide and nitrogen dioxide were prepared in argon matrices and studied using IR spectroscopy and unrestricted Hartree-Fock SCF calculations.The results indicate the formation of three different complexes NO--HF, ONNO--HF, and ONO--HF, in which the hydrogen atom of HF is bound to an oxygen atom of the base in each complex.Perturbations in the N-O stretching base submolecule modes were observed in each complex and all were blue shifted with respect to the free base.From the calculations, the unpaired electron was found to be contained in a ? antibonding orbital which is in the plane of the NO- HF and ONO-HF complexes.
- Davis, Steven R.,Andrews, Lester,Trindle, Carl O.
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p. 6027 - 6033
(2007/10/02)
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- Infrared Chemiluminescence and Laser-Induced Fluorescence Studies of Energy Disposal by Reactions of F and Cl Atoms with H2S (D2S), H2Se, H2O (D2O), and CH3OH
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The vibrational energy disposal to HF (DF), HCl (DCl), SH (SD), and CH3O and relative product formation rate constants were measured for the title reactions.The experiments were done in a fast-flow reactor with infrared emission and laser-induced fluorescence to observe nascent product state distributions for the diatomic hydride products.The CH3O vibrational and HF (DF) rotational distributions are partially relaxed, but the nascent distributions for these cases were estimated.Laser-induced fluorescence measurements showed that the SH, SD, and CH3O fragments received only 0.02-0.03 of the available energy.The v(HX)> values for group VI (group 16) hydrides, 0.45 (F + H2S), 0.44 (F + D2S), 0.48 (F + H2Se), 0.42 (F + D2O), 0.41 (Cl + H2Se), and 0.37 (Cl + D2S), are similar but distinctly smaller than for F and Cl atom reactions with group IV and VII (group 14 and 17) hydrides.The R(HX)> values, 0.18 (F + H2S), 0.19 (F + H2Se), and ca.0.14 (F + D2S), are typical for H-abstraction reactions with similar cross sections.The F + H2O/D2O systems were used to characterize the extent of secondary reactions in the fast-flow reactor.For high reagent concentrations and longer reaction times, S2 was observed in the F/Cl + H2S systems by LIF.
- Agrawalla, B. S.,Setser, D. W.
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p. 2450 - 2462
(2007/10/02)
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- Vibrational energy disposal in polyatomic ion-molecule reactions: SF6- + H, D SF5- + HF(υ), DF(υ)
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Vibrational state distributions of the , DF(ν = 0-12) ion- molecule reactions are investigated with the flowing afterglow-infrared chemiluminescence technique.The nascent distribution for the hydrogen reaction is , and for the deuterium
- Hamilton, Charles E.,Bierbaum, Veronica M.,Leone, Stephen R.
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p. 1831 - 1838
(2007/10/02)
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- The temperature dependence of hydrogen abstraction reactions: F+HCl, F+HBr, F+DBr, and F+HI
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A laser photolysis/infrared fluorescence technique has been used to study the temperature dependence of the F+HCl, F+HBr, F+DBr, and F+HI absolute rate constants in the range from 195 to 373 K.Multiphoton dissociation of SF6 with a TEA CO2 laser was used to provide a transient concentration of fluorine atoms.Their subsequent reaction with hydrogen donors was monitored by observing the appearance rate of HF(v>=1) through its infrared fluorescence.The observed rate constants show a marked nonlinear.Arrhenius behavior which is consistent with a model in which reaction takes place both via direct attack by the fluorine atom at the hydrogen end of HX and via formation of a collision complex FXH which rearranges to FHX and then dissociates to HF and X products.
- Wuerzberg, E.,Houston, P. L.
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p. 5915 - 5923
(2007/10/02)
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- Absolute rate coefficients for F+H2 and F+D2 at T=295-765K
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The rate coefficients of the F+H2 and F+D2 reactions must be accurately known over a wide temperature range if the HF and DF chemical lasers are to be properly modeled.Although the pulsed and cw chemical lasers operate at elevated temperatures (500 to 2000 K), no absolute rate data exist for T>400 K.Extension of the infrared multiphoton dissociation-infrared fluorescence technique permitted the following Arrhenius equations to be determined between 295 and 765 K: kF+H2=(1.3+/-0.25)*1014 exp; kF+D2=(6.4+/-2.2)*1013 exp; kF+H2/kF+D2=(2.1+/-0.8) exp.
- Heidner, R. F.,Bott, J. F.,Gardner, C. E.,Melzer, J. E.
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p. 4815 - 4821
(2007/10/02)
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- The temperature dependence of absolute rate constans for the F+H2 and F+D2 reactions
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Multiphoton dissociation of SF6 has been used to generate a transient concentration of fluorine atoms in mixtures with argon and H2 or D2.Absolute rate constans for the F+H2 and F+D2 reactions have been determined as a function of temperature by monitoring the appearance rate of HF or DF product chemiluminescence.In the temperature range from 190 deg K to 373 deg K the results are fit by the expressions kH=1.0*10-10 exp(-(860+/-100)/RT) and kD=9.1*10-11 exp(-(1100+/-100)/RT), both in cm3 molecule-1sec-1.These values are in rough agreement with those obtained recently using a similar technique.The value of the isotope effect kH/kD is in good agreement with two previously determined values.
- Wurzberg, E.,Houston, P. L.
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p. 4811 - 4814
(2007/10/02)
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