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  • 1
    Electronic Resource
    Electronic Resource
    The vibrational spectrum and rotational constants of difluoroethyne FC 3/4 CF. Matrix and high resolution infrared studies and ab initio calculations (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5660-5669 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Infrared spectra of the short-lived difluoroethyne molecule have been recorded in neon and argon matrices between 200 and 5000 cm−1. Fourier transform infrared spectra with a resolution of 0.004 cm−1 have been measured in the gas phase around 1350 cm−1 (ν3, ν2+ν4+ν5, hot bands) and 2150 cm−1 (ν2+ν3, ν1−ν5, hot bands). The high resolution study yields rotational parameters of the ground and all singly excited vibrational states. The interpretation of the experimental data has been guided by ab initio calculations at the SCF (self-consistent-field) level and the correlated MP2 level (Moller–Plesset second order perturbation theory) employing three different large basis sets. The theoretical calculations provide the SCF and MP2 harmonic fields as well as the SCF anharmonic force field of FCCF. The agreement between the available theoretical and experimental results is generally quite good, with the exception of the spectroscopic constants involving the trans-bending mode ν4 where more theoretical work is required. The combined use of theoretical and experimental information leads to an estimate of the equilibrium structure [D∞h, re(CC)=1.1865 A(ring), re(CF)=1.2832 A(ring)] and to recommended "best'' values for the wave numbers of all fundamental vibrations based on the matrix and high resolution infrared data and some ab initio anharmonicity constants. The present study demonstrates the advantages of a combined theoretical and experimental approach to the spectroscopy of short-lived molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461640
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  • 2
    Electronic Resource
    Electronic Resource
    High-resolution rotation–vibration spectroscopy of difluorophosphorane: A combined theoretical and experimental study (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 4603-4614 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The harmonic and anharmonic force fields of PH3F2 have been calculated at the ab initio self-consistent-field level using polarized split-valence and triple-zeta basis sets. PH3F2 has been prepared in pure form and identified unambiguously in the gas phase by Doppler-limited Fourier transform infrared spectroscopy. Guided by the theoretical predictions for the rotation–vibration spectra and the spectroscopic constants, the observed bands have been assigned and several of them rotationally analyzed, in particular ν4/2ν±27, ν2+ν4/ν2+2ν±27, and ν5/ν3+ν8. PH3F2 is found to have a D3h structure, ro(PH)=1.394(4) A(ring) and ro(PF)=1.6468(2) A(ring). The theoretical results are in good agreement with experiment, both for the structure and for the available spectroscopic constants. The present study demonstrates the advantages of a combined theoretical and experimental approach to the spectroscopy of reactive molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458700
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  • 3
    Electronic Resource
    Electronic Resource
    State-selectivity of excited-state intramolecular proton transfer in a "double'' benzoxazole: Jet spectroscopy and semiempirical calculations (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 3914-3919 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The fluorescence excitation spectra of free 2,5-bis(2'-benzoxazolyl)-hydroquinone (BBXHQ) cooled in a supersonic jet are examined. By using double-resonance saturation spectroscopy, we show that adjacent vibronic transitions, leading to either blue or red fluorescence, belong to a single molecular species in the electronic ground state. The molecular geometries of the enol and keto forms which are relevant for intramolecular transfer of a single hydrogen atom in the S1 state are obtained by the MNDO/H method. The translocation distance is calculated to be 0.43 A(ring). The complexity of the vibronic spectrum, near the electronic origin for the S0(1Ag) → S1(1Bu) transition of the enol form at 4178.1 A(ring), is attributed to vibronic coupling with the nonplanar excited keto form due to H tunneling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462930
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  • 4
    Electronic Resource
    Electronic Resource
    Additions and Corrections - The MNDOC Method, a Correlated Version of the MNDO Model (1982)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 104 (1982), S. 3783-3783 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00377a604
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  • 5
    Electronic Resource
    Electronic Resource
    Ab Initio Computation of 77Se NMR Chemical Shifts with the IGLO-SCF, the GIAO-SCF, and the GIAO-MP2 Methods (1995)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 4000-4007 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100012a021
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  • 6
    Electronic Resource
    Electronic Resource
    Ab initio calculations on monohalogenophosphanes PH2X (X=F,Cl,Br,I), and experimental detection and characterization of PH2F and PH2Cl by high resolution infrared spectroscopy (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 5585-5595 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The harmonic and anharmonic force fields of the title compounds have been calculated at the ab initio self-consistent-field level using effective core potentials and polarized double-zeta basis sets. Additional calculations for PH2F employ larger basis sets and include electron correlation. Many rovibrational constants are predicted theoretically. The infrared spectra generated from the ab initio data have guided the experimental identification of PH2F and PH2Cl in the gas phase. High resolution Fourier transform infrared spectra of these unstable molecules have been recorded for the first time. Rotational analyses for several bands are reported which provide accurate ground state constants and a precise characterization of a number of vibrationally excited states. The accuracy of the ab initio predictions for PH2F and PH2Cl is evaluated by comparisons with these experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468460
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  • 7
    Electronic Resource
    Electronic Resource
    The vibrational spectra of krypton and xenon difluoride: High-resolution infrared studies and ab initio calculations (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 1-14 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Fourier transform infrared spectra of KrF2, XeF2, and monoisotopic 136XeF2 have been recorded in the ν3 and ν1+ν3 ranges with an effective resolution of 0.003–0.007 cm−1. About 10 000 rovibrational lines belonging to cold bands and to hot bands with ν1, ν2, 2ν2, and ν3 as lower levels have been assigned and fitted. The high-resolution results from this work and from two previous studies provide a rather complete set of precise spectroscopic constants and accurate ground-state and equilibrium geometries for both molecules. In the case of 84KrF2, r0=188.2821(9) pm supersedes previous incorrect r0 values, and re=187.6930(23) pm represents the first determination of the Kr–F equilibrium distance. Ab initio calculations employing effective core potentials and polarized double-zeta basis sets have been carried out at the following levels: self-consistent-field (SCF) theory, the Møller–Plesset second order perturbation theory (MP2), and coupled cluster theory with single and double excitations (CCSD) and a perturbational treatment of triple excitations (CCSD(T)). Pronounced correlation effects are found, especially for KrF2. The agreement between the correlated theoretical and the experimental results is generally quite good. A theoretical analysis clarifies the origin of the positive α2 vibration–rotation coupling constants which have been observed for the bending vibrations in both molecules. Reliable harmonic and anharmonic force fields are presented for KrF2 and XeF2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468170
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  • 8
    Electronic Resource
    Electronic Resource
    Ab initio calculations and high resolution infrared investigation on XeF4 (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 4945-4953 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ab initio calculations employing effective core potentials and polarized triple-zeta basis sets have been carried out for XeF4 at the following levels: self-consistent-field (SCF) theory, Møller–Plesset second-order perturbation theory (MP2), and coupled cluster theory with single and double excitations and a perturbational treatment of triple excitations (CCSD(T)). Pronounced correlation effects are found, especially for the Xe–F bond length and the vibrational frequencies. The theoretical predictions for the harmonic and anharmonic force fields and the associated spectroscopic constants have guided the analysis of the experimental data. Fourier transform infrared spectra of monoisotopic 136XeF4 have been recorded between 100–1170 cm−1 with an effective resolution of 0.002–0.004 cm−1, and a rotational analysis has been performed for the ν2 band. The high resolution results provide accurate molecular parameters for the ground state and the v2=1 excited state of XeF4 and allow a precise determination of the ground state Xe–F bond length, r0=193.487(3) pm. The agreement between the experimental and the correlated theoretical results is generally quite good. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471266
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  • 9
    Electronic Resource
    Electronic Resource
    Equilibrium yield for helium incorporation into buckminsterfullerene: Quantum-chemical evaluation (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 1796-1799 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The binding energy and equilibrium constant for the endohedral He@C60 compound have been determined from ab initio and density functional (DFT) calculations. Very large grids for the numerical integration are necessary to converge the DFT results to within 0.1 kcal/mol. Gradient-corrected DFT methods incorrectly predict He@C60 to be less stable than He+C60. At the highest ab initio level employed, i.e., second-order Møller–Plesset perturbation theory (MP2) with extended basis sets and counterpoise corrections, He@C60 is bound by 2.0 kcal/mol. The equilibrium constant for He incorporation into C60 has been evaluated from Hartree–Fock and DFT interaction potentials adjusted to reproduce the MP2 binding energy. Computed equilibrium yields at 3000 atm and 900 K exceed 10%, compared with 0.1% observed in the experiment, which indicates that suitable catalysts could increase the observed yield significantly. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473336
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  • 10
    Electronic Resource
    Electronic Resource
    Ligands with Cycloalkane Backbones. IV. Dichloro{(S,S)-trans-diphenyl[(2-diphenylphosphinyl)cyclohexyl]phosphinic acid ester}palladium(II) (1998)
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 227-228 
    Details
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108270197013231
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