14333-26-7Relevant academic research and scientific papers
Mode specific internal and direct rotational predissociation in HeHF, HeDF, and HeHCl: van der Waals complexes in the weak binding limit
Lovejoy, Christopher M.,Nesbitt, David J.
, p. 5387 - 5407 (1990)
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.
INFRARED SPECTRA OF DIATOMIC HALOGEN COMPLEXES WITH HYDROGEN FLUORIDE IN SOLID ARGON AND NEON
Hunt, Rodney D.,Andrews, Lester
, p. 3769 - 3774 (1988)
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
Infrared spectra of the very weak H2--HF and O2--HF complexes in solid neon
Hunt, Rodney D.,Andrews, Lester
, p. 3781 - 3786 (1987)
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.
H/D isotope exchange between methane and magic acid (HSO 3F-SbF5): An in situ NMR study
Walspurger, Stephane,Goeppert, Alain,Haouas, Mohamed,Sommer, Jean
, p. 266 - 269 (2004)
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.
Infrared Spectra of Cyanogen Halide Complexes with Hydrogen Fluoride in Solid Argon
Hunt, Rodney D.,Andrews, Lester
, p. 5594 - 5598 (1987)
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.
XeOF2, F2OXeN≡CCH3, and XeOF 2·nHF: Rare examples of Xe(IV) oxide fluorides
Brock, David S.,Bilir, Vural,Mercier, Helene P. A.,Schrobilgen, Gary J.
, p. 3598 - 3611 (2007)
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.
Infrared spectra of HF complexes with methane, silane, and germane
Davis, Steven R.,Andrews, Lester
, p. 3765 - 3772 (1987)
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.
OPERATING CHARACTERISTICS OF A TRANSVERSE-FLOW DF- CO2 PURELY CHEMICAL LASER
COOL TA,SHIRLEY JA,STEPHENS RR
, p. 278 - 281 (1970)
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.
Slit jet infrared spectroscopy of hydrogen bonded N2HF isotopomers: Rotational Rydberg-Klein-Rees analysis and H/D dependent vibrational predissociation rates
Nesbitt, David J.,Lindeman, Theodore G.,Farrell, John T.,Lovejoy, Chris M.
, p. 775 - 785 (1994)
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.
Deuterium labeling, FTIR, and ab initio investigation of the solution-phase thermal reactions of alcohols and alkenes with hydrogen-terminated silicon surfaces
Bateman,Eagling,Horrocks,Houlton
, p. 5557 - 5565 (2000)
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.
