J. W. Bevan

Texas A&M University, College Station, TX, United States

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Publications (96)211.34 Total impact

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    ABSTRACT: Different classes of ground electronic state pairwise interatomic interactions are referenced to a single canonical potential using explicit transformations. These approaches have been applied to diatomic molecules N2, CO, H2(+), H2, HF, LiH, Mg2, Ca2, O2; argon dimer, and one-dimensional cuts through multidimensional potentials of OC-HBr, OC-HF, OC-HCCH, OC-HCN, OC-HCl, OC-HI, OC-BrCl, and OC-Cl2 using accurate semi-empirically determined interatomic Rydberg-Klein-Rees (RKR) and morphed intermolecular potentials. These different bonding categories are represented in these systems which vary from van der Waals, halogen bonding, hydrogen bonding to strongly bound covalent molecules with binding energies covering three orders of magnitude from 84.5 cm(-1) to 89600.6 cm(-1) in ground state dissociation energies. Such approaches were then utilized to give a unified perspective on the nature of bonding in the whole range of diatomic and intermolecular interactions investigated.
    The journal of physical chemistry. A. 07/2014;
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    ABSTRACT: A five-dimensional compound-model morphed (CMM) potential has been generated for the halogen bonded intermolecular interaction 16O12C-79Br35Cl based on a fit to the currently generated infrared and previously available microwave spectroscopic data. The experimentally determined blue frequency shift of the 16O12C stretching frequency on complexation with 79Br35Cl is found to be Δν = 12.89643(28) cm-1 indicating a more strongly bound complex than in OC-35Cl2. Re center-of-mass to center-of-mass distance of 4.270(7) Å and dissociation energies De = 778(70) cm-1 and D0 = 605(70) cm-1 are predicted from the CMM potential and also compared with the corresponding values of Re = 4.742(3) Å and De = 544(5) cm-1 and D0 = 397(5) cm-1 for 16O12C-35Cl2. The molecular dynamics, binding energy and other molecular parameters of OC-BrCl are also compared with the hydrogen bonded dimers OC-HX (X = F, Cl, Br) giving further insight into the characteristics of the complex.
    Chemical Physics 11/2013; · 1.96 Impact Factor
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    ABSTRACT: Potential morphing has been applied to the investigation of proper blue frequency shifts, Δν0 in CO, the hydrogen acceptor complexing in the hydrogen bonded series OC-HX (X=F, Cl, Br, I, CN, CCH). Linear correlations of morphed hydrogen bonded ground dissociation energies D0 with experimentally determined Δν0 free from matrix and solvent effects demonstrate consistency with original tenets of the Badger-Bauer rule [J. Chem. Phys. 5, 839-51(1937)]. A model is developed that provides a basis for explaining the observed linear correlations in the range of systems studied. Furthermore, the generated calibration curve enables prediction of dissociation energies for other related but different complexes. The latter include D0 for H2O-CO, H2S-CO and OC-HOCH3 which are predicted by interpolation and found to be 355(13), 171(11) and 377(14) cm(-1) respectively from available experimentally determined proton acceptor shifts. Results from this study will also be discussed in relation to investigations in which CO has been used as a probe of heme protein active sites.
    The Journal of Physical Chemistry A 07/2013; · 2.77 Impact Factor
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    ABSTRACT: Rovibrational manifolds in low frequency intermolecular vibrations of prototypical hydrogen-bonded interactions OC–HX (X = F, Cl, CN) are reported using a near infrared quantum cascade cw supersonic jet spectrometer. (i) OC–HCl is studied to evaluate future capabilities of the QCL spectrometer. (ii) Analysis of OC–HF demonstrates applicability to vibrations greater than 80 cm−1 above the ground state. ν51 band origins in OC–1H35Cl and OC–1H19F are 48.9944(2) and 81.96825(12) cm−1 respectively. (iii) The corresponding intermolecular ν71 band origin of OC–HCN is 34.63742(18) cm−1 and its corresponding rovibrational spectrum made available for attempted detection in interstellar space. Analysis of ν2, ν2+ν71-ν71, ν2+ν71, and ν2+ν61 vibrations in OC–HCN also enables generation of its 5-dimensional semi-empirical intermolecular potential. Structural and other properties of OC–HCN are then compared with corresponding properties predicted using morphed potentials for the homologous series OC–HX (X = F, Cl, Br, I). These results permit investigation of blue shifts in OC vibrations for this homologous series.
    Chemical Physics 12/2012; 409:1–10. · 1.96 Impact Factor
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    ABSTRACT: A recently generated six-dimensional vibrationally-complete compound-model morphed (CMM-RS) potential for the pairwise interaction between OC and HF is used to predict spectroscopic and other properties of the isomer CO–HF. The equilibrium dissociation energy and internuclear diatomic center-of-mass center-of-mass distances are evaluated respectively as De = 643(10) cm−1 and Re = 3.442(2) Å with an energy difference ΔE between the OC–HF and CO–HF minima in the potential energy surface of 667(10) cm−1. The CO–HF isomer is also predicted to have a local minimum state with dissociation energy D0 = 310.5(50) cm−1 which corresponds to 432(10) cm−1 above the ground state of OC–HF. Band origins for its fundamental vibrations are predicted to be: ν1 = 3938.85(100) cm−1, ν2 = 2134.52(100) cm−1, ν3 = 80.56(100) cm−1, ν41 = 205.65(100) cm−1, and ν51 = 39.55(100) cm−1 and can be compared with currently available data from matrix isolation and other spectroscopic techniques. Such predictions will also facilitate future gas phase spectroscopic investigations of the CO–HF isomeric species and ultimately critical evaluation of the predictive capabilities of the available CMM-RS potential as well as those of previously published ab initio potentials.
    Journal of Molecular Structure 09/2012; 1023:43–48. · 1.40 Impact Factor
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    ABSTRACT: Spectroscopic studies of the OC:HCCH complex are reported using a continuous supersonic slit jet spectrometer with broadband frequency mode-hop free tunable infrared quantum cascade lasers (QCL), centered at 4.4 and 4.6 μm. This Letter includes an extended analysis of the ν3 CO stretching vibration frequency, and investigation of the ν3 + ν91 − ν91 hot band, the ν3 + ν91 and ν3 + ν81 combination bands for OC–HCCH. The ground state low frequency bend, ν91, is determined at 20.48361(20) cm−1. The generated rovibrational data is incorporated with previously determined information and used to generate a four-dimensional compound-model morphed potential with radial correction, giving further insight into the molecular dynamics of this complex.
    Chemical Physics Letters 01/2012; 522:17–22. · 2.15 Impact Factor
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    ABSTRACT: Transitions associated with the vibrations ν₁, ν₁ + ν(b)¹, ν₁ + ν₅¹, and ν₁ + ν₅¹ - ν₅¹ of the complex OC···Cl₂ have been rovibrationally analyzed for several isotopologues involving isotopic substitutions in Cl₂. Spectra were recorded using a recently constructed near-infrared (4.34 to 4.56 μm), quantum-cascade laser spectrometer with cw supersonic slit jet expansion. Spectral analysis allowed precise determination of the ν₅¹ intermolecular vibration of OC-³⁵Cl₂ to be 25.977637(80) cm⁻¹. These results were incorporated with other previously determined data into a spectroscopic database for generation of a five-dimensional morphed potential energy surface. This compound-model morphed potential with radial shifting (CMM-RS) was then used to make more accurate predictions of properties of the OC-³⁵Cl₂ complex including D(e) = 544(5) cm⁻¹, D₀ = 397(5) cm⁻¹, ν₃ = 56.43(4) cm⁻¹, and ν(b)¹ = 85.43(4) cm⁻¹. The CMM-RS potential determined for OC-Cl₂ was also used to compare quantitatively many of the inherent properties of this non-covalent halogen bonded complex with those of the closely related hydrogen-bonded complex OC-HCl, which has a similar dissociation energy D₀. We found that in the ground state, the CO bending amplitude is larger in OC-Cl₂ than in OC-HCl.
    The Journal of Physical Chemistry A 12/2011; 116(4):1213-23. · 2.77 Impact Factor
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    ABSTRACT: A 6-dimensional vibrationally-complete compound-model morphed potential with radial shifting (CMM-RS) has been generated for the hydrogen-bonded dimer OC–HF. Four morphing parameters only are optimized correcting for inadequacies in the underlying ab initio potential. The morphing transformation utilized a rotationally resolved spectroscopic database composed of microwave and near infrared spectroscopic information. Band origin vibrational frequencies are fitted to an average standard deviation of 0.016cm−1. The equilibrium rotational constant of OC–HF is determined to be Be=3345.68(30)MHz, equilibrium center of mass CO to center of mass HF distance, Re=3.598(1)Å, and equilibrium dissociation energy De=1310(10)cm−1. Ground state dissociation energy D0=742.5(50)cm−1, first order anharmonic constants and other properties of the complex are also evaluated. Characteristics of the CMM-RS potential can also be compared with predictions using previous ab initio potentials. Limitations of the morphing methodology and its potential applications are also discussed.
    Chemical Physics 11/2011; · 1.96 Impact Factor
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    ABSTRACT: A broadband v3 sub-Doppler spectrum of HCN has been recorded in the range 3340–3280 cm−1 using a single frequency continuously scanable computer-controlled color center laser optothermal molecular beam spectrometer. Absolute frequencies for rovibrational transitions R(9) through P(9) have been determined to an accuracy ≤ 20 MHz or 2 parts in 107. An unconstrained five-parameter fit to this datum results in molecular constants: B″ = 1.47822146(182), D″ = 2.881(23) × 10−6, B′ = 1.46779974(154), D′ = 2.863(18) × 10−6, and v0 = 3311.47758(2) cm−1, respectively.
    Canadian Journal of Chemistry 02/2011; 63(7):1870-1873. · 0.96 Impact Factor
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    ABSTRACT: The HI homodimer was found to have structural and vibrational properties unlike any other previously studied (HX)(2) system, with X = F, Cl, and Br. The infrared spectrum of (HI)(2) is also observed to be distinctly different from the other members of the series. In addition, the interaction energy of the (HI)(2) dimer has been calculated using the coupled-cluster with singles, doubles, and perturbative triples [CCSD(T)] level of theory. A four-dimensional morphed intermolecular potential has been generated and then morphed using available near infrared and submillimeter spectroscopic data recorded in supersonic jet expansions. The morphed potential is found to have a single global minimum with a symmetric structure having C(2h) symmetry. The equilibrium dissociation energy is found to be 359 cm(-1) with the geometry in Jacobi coordinates of R(e) = 4.35 Å, θ(1) = 43°, θ(2) = 137°, and φ = 180°. The infrared spectrum is characterized by pairs of excited vibrational states resulting from the coupling of the two HI stretching modes. A qualitative model using a quadratic approximation has been fitted to obtain an estimate of this coupling. Furthermore, a morphed intermolecular potential for the vibrationally excited system was also obtained that gives a quantitative estimate of the shift in the potential due to the excitation. The submillimeter analysis is consistent with a ground state having its highest probability as a paired hydrogen bond configuration with R(0) = 4.56372(1) Å and an average angle θ=cos(-1)(<cos(2) θ>(1/2)) = 46.40(1)° (between the diatom center of mass∕center of mass axis and direction of each component hydrogen iodide molecule). On monodeuteration, however, the ground state is predicted to undergo an anomalous structural isotope change to an L-shaped HI-DI structure with highest probability at R(0) = 4.51 Å, θ(1) = 83°, θ(2) = 177°, and φ = 180°. These results provide a test for large scale ab initio calculations and have implications for the interpretation of photoinduced chemistry and other properties of the dimer.
    The Journal of Chemical Physics 02/2011; 134(6):064317. · 3.12 Impact Factor
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    ABSTRACT: Design and testing of a THz sensor ultimately to be capable of operating from 0.068 to 8.1 THz are presented. Results for modular approaches in the mm and submm spectral regions are reported utilizing cavity-enhanced techniques. Investigations indicate ppq levels of detection for molecular species with 1.0 Debyes dipole moment.
    01/2011;
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    ABSTRACT: Application of a QCL based spectrometer to cw supersonic slit jet expansions of CO and HX (X= F, Cl, CN, CCH) are reported. Spectroscopic analysis of fundamental, combination and hot bands of the CO stretching vibrations provide ro-vibrational parameters for low frequency intermolecular vibrations that can be incorporated in determination of morphed potentials for the respective dimers.
    01/2011;
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    ABSTRACT: An extended analysis of the noncovalent interaction OC:HI is reported using microwave and infrared supersonic jet spectroscopic techniques. All available spectroscopic data then provide the basis for generating an accurately determined vibrationally complete semiempirical intermolecular potential function using a four-dimensional potential coordinate morphing methodology. These results are consistent with the existence of four bound isomers: OC-HI, OC-IH, CO-HI, and CO-IH. Analysis also leads to unequivocal characterization of the common isotopic ground state as having the OC-HI structure and with the first excited state having the OC-IH structure with an energy of 3.4683(80) cm(-1) above the ground state. The potential is consistent with the following barriers between the pairs of isomers: 382(4) cm(-1) (OC-IH/OC-HI), 294(5) cm(-1) (CO-IH/CO-HI), 324(3) cm(-1) (OC-IH/CO-IH), and 301(2) cm(-1) (OC-HI/CO-HI) defined with respect to each lower minimum. The potential is also determined to have a linear OC-IH van der Waals global equilibrium minimum structure having R(e)=4.180(11) Å, θ(1)=0.00(1)°, and θ(2)=0.00(1)°. This is differentiated from its OC-HI ground state hydrogen bound structure having R(0)=4.895(1) Å, θ(1)=20.48(1)°, and θ(2)=155.213(1)° where the distances are defined between the centers of mass of the monomers and θ(1) and θ(2) as cos(-1)[<cos(2) θ(i)>(1/2)] for i=1 and 2. A fundamentally new molecular phenomenon - ground state isotopic isomerization is proposed based on the generated semiempirical potential. The protonated ground state hydrogen-bonded OC-HI structure is predicted to be converted on deuteration to the corresponding ground state van der Waals OC-ID isomeric structure. This results in a large anomalous isotope effect in which the R(0) center of mass distance between monomeric components changes from 4.895(1) to 4.286(1) Å. Such a proposed isotopic effect is demonstrated to be a consequence of differential zero point energy factors resulting from the shallower nature of hydrogen bonding at a local potential minimum (greater quartic character of the potential) relative to the corresponding van der Waals global minimum. Further consequences of this anomalous deuterium isotope effect are also discussed.
    The Journal of Chemical Physics 11/2010; 133(18):184305. · 3.12 Impact Factor
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    ABSTRACT: A parameterized compound-model morphed intermolecular potential energy surface has been generated for the dimer OC:HBr. This morphed potential is determined by fitting experimentally available gas phase spectroscopic data and found to have a global minimum with a well depth of 564(5) cm(-1) and linear (16)O(12)C-H(79)Br geometry having center of mass to center of mass distance R = 4.525(7) A. The linear isomers (12)C(16)O-H(79)Br and (16)O(12)C-(79)BrH are determined with a corresponding well depth of 273(7) and 269(2) cm(-1) having R = 4.35(4) and 4.24(3) A, respectively. This results in a DeltaE of 293(9) cm(-1) between the global potential energy minimum and the minima in the two higher energy isomers. The generated potential is compared with the corresponding OC:HCl morphed potential. Differences in the morphing parameters are attributed to different contributions to the interaction energy. It is found that the counterpoise method successfully corrected the basis set superposition error in OC:HCl, but was under corrected by 16(7)% in OC:HBr.
    Physical Chemistry Chemical Physics 07/2010; 12(26):7258-65. · 3.83 Impact Factor
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    ABSTRACT: Observed rotational–vibrational transitions of HI dimer in the geared bending mode, centered at 511.9GHz, are reported. This ∼50kHz spectrum was recorded using a co-axially configured pulsed jet submillimeter spectrometer and hyperfine structure of R(J) and P(J) transitions from the quadrupole moments of iodine nuclei are completely resolved for low-J transitions. Analysis of hyperfine patterns was carried out using a theoretical approach accounting for the large amplitude motion effects and hyperfine matrix elements within and between vibrational states. The submillimeter analysis is consistent with a vibrationally averaged ground state Rcm=4.56372(1)Å and average bending angle θ=46.405(1)°.
    Chemical Physics Letters 01/2009; 482(4):180-188. · 2.15 Impact Factor
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    ABSTRACT: The design and development of a fast sweep submillimeter and THz spectrometer based on solid-state components is presented. A prototype laboratory model of such a spectrometer will be described and some performance characteristics as well as potential applications emphasized.
    Infrared, Millimeter and Terahertz Waves, 2008. IRMMW-THz 2008. 33rd International Conference on; 10/2008
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    ABSTRACT: Investigations of the lowest Σ-bending vibrations of Ar–DBr (v = 0) and Ar–HBr (v = 1) are reported using a co-axially configured submillimeter supersonic jet spectrometer. The v = 1 spectra were obtained using glow discharge excitation. Analyses of hyperfine substructure in these spectra provide accurate molecular parameters for Ar–DBr and Ar–BrD isomeric states, direct determination of their corresponding isomerization energies, and respective parameters in the v = 1 HBr stretching vibration of the Ar–HBr isotopomer. This experimental data provides a sensitive probe of the relative energies of potential minima for previously determined 3-D Ar–HBr morphed potential and compared with results from extrapolations to the CCSD(T)/CBS limit.
    Chemical Physics Letters 01/2008; 460:525-530. · 2.15 Impact Factor
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    ABSTRACT: The current status in the development of a phase and frequency stabilized co-axially configured submillimeter supersonic jet spectrometer will be described. The performance characteristics of the spectrometer will be illustrated by investigations of non-covalent interactions including van der Waals and hydrogen bonded complexes.
    01/2008;
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    ABSTRACT: An alternative approach to morphing the potential energy surfaces of non-covalent interactions is introduced in which morphed potentials are generated as linear combinations of ab initio potentials computed at different levels of theory. The parameterized compound-model chemistry approach, developed here, does not require scaling, shifting and dilation transformations used in previous morphing studies. This new morphing approach is applied to OC–HCl and found to be of similar accuracy as the previous morphing method. Also, consideration is given to the additional possibility that this new approach may lead to transferable empirical parameters.
    Chemical Physics Letters 01/2008; 460(1):352-358. · 2.15 Impact Factor
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    ABSTRACT: (Microwave spectra of the four isotopologue/isotopomers, HI-(12)C(16)O(2), HI-(12)C(18)O(2), HI-(12)C(18)O(16)O, and HI-(12)C(16)O(18)O, have been recorded using pulsed-nozzle Fourier transform microwave spectroscopy. In the last two isotopomers, the heavy oxygen atom tilted toward and away from the HI moiety, respectively. Only b-type Ka = 1 <-- 0 transitions were observed. Spectral analysis provided molecular parameters including rotational, centrifugal distortion, and quadrupole constants for each isotopomer. Then, a four-dimensional intermolecular energy surface of a HI-CO2 complex was generated, morphing the results of ab initio calculations to reproduce the experimental data. The morphed potential of HI-(12)C(16)O(2) had two equivalent global minima with a well depth of 457(14) cm(-1) characterized by a planar quasi-T-shaped structure with the hydrogen atom tilted toward the CO2 moiety, separated by a barrier of 181(17) cm(-1). Also, a secondary minimum is present with a well depth of 405(14) cm(-1) with a planar quasi-T-shaped structure with the hydrogen atom tilted away from the CO2 moiety. The ground state structure of HI-(12)C(16)O(2) was determined to have a planar quasi-T-shaped geometry with R = 3.7717(1) A, thetaOCI = 82.30(1) degrees , thetaCIH = 71.55(1) degrees . The morphed potential obtained is now available for future studies of the dynamics of photoinitiated reactions of this complex.
    The Journal of Physical Chemistry A 11/2007; 111(47):11976-85. · 2.77 Impact Factor