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  • 1
    Electronic Resource
    Electronic Resource
    Slit jet infrared spectroscopy of hydrogen bonded N2HF isotopomers: Rotational Rydberg–Klein–Rees analysis and H/D dependent vibrational predissociation rates (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 775-785 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: 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 one-dimensional (1D) potential surface such as hydrogen bond length (RH-bond), harmonic force constant (kσ), 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 vHF=0 or 1 is excellent, and provides effective 1D potentials for the stretching coordinate between 3.39 and 3.75 A(ring). There is a 43 cm−1 (∼10%) strengthening of the hydrogen bond upon HF vibrational excitation, as quantitatively reflected in the experimental redshifts and the shape of the RKR potentials for vHF=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∼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(v=1)+DF(v=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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466560
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic Properties of Intermetallic Compounds between the Lanthanides and Nickel or Cobalt (1966)
    s.l. : American Chemical Society
    Inorganic chemistry 5 (1966), S. 105-109 
    Details
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ic50035a025
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetic behavior of metal derivatives of substituted phenylazo-5-pyrazolones (1971)
    s.l. : American Chemical Society
    Inorganic chemistry 10 (1971), S. 1180-1183 
    Details
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ic50100a016
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  • 4
    Electronic Resource
    Electronic Resource
    High-resolution infrared spectroscopy of DF trimer: A cyclic ground state structure and DF stretch induced intramolecular vibrational coupling (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 5985-5989 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present high resolution, infrared laser absorption spectra of (DF)3 in a slit supersonic jet expansion. In contrast to previous structureless near IR spectra of (HF)3, the (DF)3 data reveal clear rotational structure characteristic of a cyclic, 6-membered "ring,'' and therefore provide the first accurate experimental evidence for the equilibrium geometry of any hydrogen fluoride oligomer beyond the well-studied dimer. Furthermore, the spectra display homogeneous rotational fine structure 2–3 orders of magnitude in excess of what could be anticipated from a single vibrational band. Analysis of this fine structure elucidates a novel IVR mechanism which involves single hydrogen bond cleavage, and consequent opening of the (DF)3 ring on the 40 ps time scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464860
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  • 5
    Electronic Resource
    Electronic Resource
    High-resolution infrared overtone spectroscopy of ArHF via Nd:YAG/dye laser difference frequency generation (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 7967-7978 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The first high-resolution spectra of ArHF excited to the vHF=2←0 manifold near 7800 cm−1 are recorded via direct infrared absorption in a slit supersonic expansion. The tunable difference frequency light is generated via nonlinear subtraction of a cw Nd:YAG laser from a tunable cw ring dye laser in temperature phase matched LiNbO3, and permits continuous single-mode access to the 1–2 μm near-IR region. Rotationally resolved spectra are presented for the pure HF stretching overtone (2000)←(0000), as well as for combination band excitation into the Σ bend (2100)←(0000) and Π bend (2110)←(0000) internal rotor levels built on the vHF=2 overtone stretch. Local perturbations in the Π bend spectrum are observed which arise from a resonant crossing of rotational levels with the (2002) van der Waals stretch and allow spectroscopic analysis of this state. Nonresonant coupling between the Σ and Π bend vibrational levels is evidenced by anomalous P branch/R branch transition intensities and is analyzed as Coriolis interactions in a tumbling, hindered rotor. The spectra reveal Doppler limited line shapes [Δν=79(11) MHz] characteristic of the temperature and geometry of the slit expansion. An upper limit of Δνprediss≤2 MHz Lorentzian broadening is established, indicating an 80 ns lower limit to the predissociation lifetime. Comparison of intermolecular vibrational levels in ArHF vHF=0, 1, and 2 indicates a systematic increase in both angular anisotropy and radial well depth upon excitation of the high-frequency HF stretch. In conjunction with previous results from the vHF=1 and vHF=0 vibrational levels, these studies provide the necessary data for fitting an atom+diatom potential energy surface as a function of all intermolecular and intramolecular internal degrees of freedom.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463471
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  • 6
    Electronic Resource
    Electronic Resource
    Breaking symmetry with hydrogen bonds: Vibrational predissociation and isomerization dynamics in HF–DF and DF–HF isotopomers (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 9313-9331 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High-resolution near-IR spectra of jet-cooled HF–DF and DF–HF isotopomers are presented and analyzed for fundamental excitation in the HF-stretching region (3870 cm−1–3960 cm−1) and DF-stretching region (2840 cm−1–2880 cm−1), based on direct absorption of tunable IR difference frequency radiation in a slit-jet supersonic expansion (10 K). Spectra are obtained for excitation of all four stretching modes, *HF–DF, HF–*DF, *DF–HF, and DF–*HF (* denotes the vibrationally excited subunit), which probe both the hydrogen/deuterium bond donor and acceptor moieties in the complex. Vibrational redshifts and predissociation broadening measurements are compared with full 6D quantum calculations on theoretical HF dimer potential surfaces, which exhibit trends in qualitatively good agreement with experiment. Each of the three DF-stretch-excited bands are fit to spectroscopic precision (Δν(approximately-less-than)0.0001 cm−1) by conventional high-resolution rotational analyses, whereas each of the four corresponding HF-stretch-excited bands appear extensively perturbed (Δν≈0.01 cm−1). This H/D isotope effect is interpreted as vibrational state mixing of the HF-stretch-excited species with a dense manifold of combination band states built on DF-stretch excitation, and therefore reflects intermolecular energy flow in the complex. Such vibrational state mixing is further corroborated by observation of "dark'' state transitions that can be tentatively assigned to *HF–DF isomer interacting with the nearly isoenergetic DF–*HF isomer. This state mixing would correspond to a vibrationally promoted "isomerization'' over the tunneling barrier, and yield a spectroscopic measure of the difference in hydrogen bond dissociation energies [ΔD0=74.7(5) cm−1] for the HF–DF and DF–HF isotopomers. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471677
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  • 7
    Electronic Resource
    Electronic Resource
    Isotopic substitution of a hydrogen bond: A near infrared study of the intramolecular states in (DF)2 (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 8197-8209 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High resolution near infrared spectra of the two high frequency intramolecular modes in (DF)2 have been characterized using a slit-jet infrared spectrometer. In total, four pairs of vibration–rotation–tunneling (VRT) bands are observed, corresponding to K=0 and K=1 excitation of both the ν2 ("bound'') and ν1 ("free'') intramolecular DF stretching modes. Analysis of the rotationally resolved spectra provides vibrational origins, rotational constants, tunneling splittings and upper state predissociation lifetimes for all four states. The rotational constants indicate that the deuterated hydrogen bond contracts and bends upon intramolecular excitation, analogous to what has been observed for (HF)2. The isotope and K dependence of tunneling splittings for (HF)2 and (DF)2 in both intramolecular modes is interpreted in terms of a semiclassical 1-D tunneling model. High resolution line shape measurements reveal vibrational predissociation broadening in (DF)2: 56(2) and 3(2) MHz for the ν2 (bound) and ν1 (free) intramolecular stretching modes, respectively. This 20-fold mode specific enhancement parallels the ≥30-fold enhancement observed between analogous intramolecular modes of (HF)2, further elucidating the role of nonstatistical predissociation dynamics in such hydrogen bonded clusters. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471604
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  • 8
    Electronic Resource
    Electronic Resource
    Pairwise and nonpairwise additive forces in weakly bound complexes: High resolution infrared spectroscopy of ArnDF (n=1,2,3) (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 2395-2411 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High resolution infrared spectra of the vDF=1←0 stretch in ArnDF (n=1–3) have been recorded using a slit-jet infrared spectrometer. Analysis of the rotationally resolved spectra provides vibrationally averaged geometries and vibrational origins for a DF chromophore sequentially "solvated'' by Ar atoms. Calculations using pairwise additive Ar–Ar and Ar–DF potentials predict lowest energy equilibrium structures consistent with the vibrationally averaged geometries inferred spectroscopically. Variational calculations by Ernesti and Hutson [A. Ernesti and J. M. Hutson, Faraday Discuss. Chem. Soc. (1994)] using pairwise additive potentials predict rotational constants which are in qualitative agreement with, but consistently larger than, the experimental values. The inclusion of nonpairwise additive (three-body) terms improves the agreement, though still not to within the uncertainty of the pair potentials. The vibrational redshifts of 8.696, 11.677, and 14.461 cm−1 for n=1–3, respectively, reflect a nonlinear dependence of the redshift on the number of Ar atoms. Both the variational calculations of Ernesti and Hutson and diffusion quantum Monte Carlo calculations [M. Lewerenz, J. Chem. Phys. (in press)] using pairwise additive potentials systematically overpredict the magnitude of these redshifts, further signifying the need for corrective three-body terms. Analysis of the ArnDF (n=2,3) rovibrational line shapes reveals an upper limit to homogeneous broadening on the order of 2–3 MHz, consistent with vibrational predissociation lifetimes in excess of 50 ns. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469663
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  • 9
    Electronic Resource
    Electronic Resource
    Probing three-body intermolecular forces: Near-infrared spectroscopy of Ar2HF and Ar2DF van der Waals modes (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 9421-9440 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Four intermolecular vibrational states of the weakly bound complexes Ar2HF and Ar2DF have been studied via high-resolution infrared spectroscopy. The vibrations are accessed as combination bands built on the v=1 HF or DF intramolecular stretch. These van der Waals vibrational states correlate adiabatically with j=1 motion of a hindered HF/DF rotor, corresponding to librational motion either in, or out of, the molecular plane. The vibrational origins of the Ar2HF in-plane and out-of-plane bends are 4008.9665(24) and 4035.174 41(86) cm−1, respectively, which are 62.374 and 88.582 cm−1 above the origin of the intermolecular ground state in the vHF=1 manifold. For Ar2DF, the in-plane and out-of-plane origins are 2939.836 63(4) and 2967.101 29(5) cm−1, respectively, which correspond to intermolecular bending frequencies in the vDF=1 manifold of 44.852 and 72.117 cm−1. Two-dimensional angular calculations are presented which solve for the hindered rotor HF/DF eigenfunctions and eigenvalues on a pairwise additive potential constructed using a rigid Ar2 framework; the predicted bending frequencies reproduce the correct energy ordering of the vibrational levels, but are systematically greater than experimentally observed. Rigorous full five-dimensional theoretical calculations of the intermolecular vibrational frequencies by Ernesti and Hutson [Phys. Rev. A 51 239 (1995)] on the full pairwise additive surface are found to be as much as 11% higher than the experimental values, indicating the presence of three-body repulsive contributions to the true angular potential. Inclusion of conventional three-body dispersion and induction terms can only account for a minority (≈1/3) of the observed discrepancies. The majority (≈2/3) of the vibrational shifts can be attributed to three-body "exchange'' effects, i.e., the strongly anisotropic interaction of the HF/DF dipole with an exchange quadrupole formed by Ar–Ar. Inclusion of all three nonadditive terms (dispersion, induction, and exchange) improves the agreement with experiment by up to an order of magnitude. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472777
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  • 10
    Electronic Resource
    Electronic Resource
    High-Resolution Infrared Overtone Spectroscopy of N2-HF:Vibrational Red Shifts and Predissociation Rate as a Function of HF Stretching Quanta (1994)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 6068-6074 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100075a005
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