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1 Oct 2000

Volume 113, Issue 13, pp. 5115-5579

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Full dimensional quantum calculations of the CH4+H→CH3+H2 reaction rate

Fermín Huarte-Larrañaga and Uwe Manthe

J. Chem. Phys. 113, 5115 (2000); http://dx.doi.org/10.1063/1.1311802 (4 pages) | Cited 99 times

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Accurate full-dimensional quantum mechanical calculations are reported for the CH4+H→CH3+H2 reaction employing the Jordan–Gilbert potential energy surface. Benchmark results for the thermal rate constant and the cumulative reaction probability are presented and compared to classical transition state theory as well as reduced dimensionality quantum scattering calculations. The importance of quantum effects in this system is highlighted. © 2000 American Institute of Physics.
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82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)
82.20.Pm Rate constants, reaction cross sections, and activation energies
82.20.Kh Potential energy surfaces for chemical reactions
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions

Eley–Rideal reaction of O+ with oxidized Si(100)

C. L. Quinteros, T. Tzvetkov, and D. C. Jacobs

J. Chem. Phys. 113, 5119 (2000); http://dx.doi.org/10.1063/1.1311780 (4 pages) | Cited 10 times

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The reaction of 10–60 eV O+ ions with a silicon oxide thin film produces scattered O2−. Isotopic labeling experiments demonstrate that the O2− product is formed by an abstraction reaction and not by physical sputtering. Energy and angle resolved detection reveals a correlation between the scattered and incident particle momenta, indicative of a direct process in which the incoming oxygen atom reacts with an adsorbed oxygen atom through an Eley–Rideal mechanism. © 2000 American Institute of Physics.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)
82.20.Tr Kinetic isotope effects including muonium
34.35.+a Interactions of atoms and molecules with surfaces

Improved efficiency with variational Monte Carlo using two level sampling

M. Dewing

J. Chem. Phys. 113, 5123 (2000); http://dx.doi.org/10.1063/1.1311288 (3 pages) | Cited 4 times

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A two level sampling method is applied to variational Monte Carlo (VMC) that samples the one- and two-body parts of the wave function separately. The method is demonstrated on a single Li2 molecule in free space and 32 H2 molecules in a periodic box. This simple modification increases the efficiency of a VMC simulation by up to 72%. © 2000 American Institute of Physics.
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31.15.xt Variational techniques
02.30.Xx Calculus of variations
02.30.Yy Control theory
02.50.Ng Distribution theory and Monte Carlo studies

Dynamics of collapse of flexible polyampholytes

Namkyung Lee and D. Thirumalai

J. Chem. Phys. 113, 5126 (2000); http://dx.doi.org/10.1063/1.1312267 (4 pages) | Cited 8 times

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We provide a theory for the dynamics of collapse of flexible polyampholytes (PAs) using Langevin equation. Metastable pearl-necklace structures form in a time scale proportional to N4/5 (N is the number of monomers). In the late stage of collapse the pearls merge with the largest one growing at the expense of smaller ones (Lifshitz–Slyozov mechanism). The time scale for this process is τcoll ∼ N. Counterion-mediated collapse of strongly charged polyelectrolytes (PEs) follow a similar route to the globular state. Simulations support the proposed collapse mechanism for PAs and PEs. © 2000 American Institute of Physics.
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36.20.Ey Conformation (statistics and dynamics)
82.45.-h Electrochemistry and electrophoresis
33.15.Hp Barrier heights (internal rotation, inversion, rotational isomerism, conformational dynamics)

On the origin of planarity in Al5− and Al5 clusters: The importance of a four-center peripheral bond

Grant D. Geske, Alexander I. Boldyrev, Xi Li, and Lai-Sheng Wang

J. Chem. Phys. 113, 5130 (2000); http://dx.doi.org/10.1063/1.1311966 (4 pages) | Cited 19 times

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Ab initio calculations were combined with anion photoelectron spectroscopy to unravel the structural origin of Al5 and Al5−. Well-resolved photoelectron spectra of Al5− were obtained and compared to theoretical calculations performed at various levels of theory. It was shown that the best agreement between the experimental and theoretical data is for a planar C2v structure. Analyses of the electronic structure and molecular orbitals revealed that the planarity in Al5 and Al5− are due to the presence of a four-center peripheral bond that is common in a whole family of planar pentaatomic species recently uncovered. © 2000 American Institute of Physics.
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36.40.Mr Spectroscopy and geometrical structure of clusters
33.15.Bh General molecular conformation and symmetry; stereochemistry
31.15.A- Ab initio calculations
33.60.+q Photoelectron spectra

Acetylenic C–H and methyl C–D bond fission in photodissociation of vibrationally excited propyne-d3

X. Chen, Y. Ganot, I. Bar, and S. Rosenwaks

J. Chem. Phys. 113, 5134 (2000); http://dx.doi.org/10.1063/1.1312282 (4 pages) | Cited 20 times

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Vibrational preexcitation of a state containing three quanta of C–H stretch (3ν1) results in C–H acetylenic and C–D methyl bond rupture in the ∼243.1 nm photolysis of CD3C�CH, in contrast to previous observations of the almost isoenergetic 193 nm photodissociation of propynes. The C–D bond fission is the dominant pathway with a D/H branching ratio of 2.0±0.5 at a combined energy of ∼50 830 cm−1. The average translational energies of D and H atoms are nearly identical, although the C–H acetylenic and C–D methyl bond energies differ quite extensively, pointing to different dynamics on the involved potential energy surfaces. © 2000 American Institute of Physics.
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33.80.Gj Diffuse spectra; predissociation, photodissociation
82.50.Bc Processes caused by infrared radiation
82.50.Hp Processes caused by visible and UV light
82.20.Kh Potential energy surfaces for chemical reactions

The HCO2 potential energy surface: Stationary point energetics and the HOCO heat of formation

Timothy V. Duncan and Charles E. Miller

J. Chem. Phys. 113, 5138 (2000); http://dx.doi.org/10.1063/1.1312824 (3 pages) | Cited 31 times

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The energies of six stationary points on the OH+CO→HOCO→H+CO2 potential energy surface have been calculated using the G3 and CBS-QB3 methods. An analysis combining ab initio and experimental enthalpies yielded ΔHf298 K (trans-HOCO) = −42.9±1.5 kcal mol−1 (−43.8±1.4 kcal mol−1) at the G3(CBS-QB3) level of theory. These results confirm the revised HOCO heat of formation derived from photoionization spectroscopy and suggest that the HOCO potential well is 8.8 kcal mol−1 shallower than previously thought. We discuss the implications of these results for accurate Rice–Ramsperger–Kassel–Marcus modeling or quantum mechanical scattering calculations of the OH+CO reaction. © 2000 American Institute of Physics.
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82.20.Kh Potential energy surfaces for chemical reactions
82.60.Cx Enthalpies of combustion, reaction, and formation
33.80.Eh Autoionization, photoionization, and photodetachment

Evidence for orientational tunneling of CO intercalated in C60: A nuclear magnetic resonance study

M. Tomaselli, D. W. Knecht, I. Holleman, G. Meijer, and B. H. Meier

J. Chem. Phys. 113, 5141 (2000); http://dx.doi.org/10.1063/1.1312866 (4 pages) | Cited 4 times

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We characterize the low-temperature dynamics of CO intercalated in C60 using NMR spectroscopy. CO in C60 is found to be dynamically inhomogeneous below 30 K: The 13CO line shapes reflect a dynamic disorder to static disorder transition, with only quantum tunneling among equivalent orientations in a local S6 symmetry potential remaining. The increased hindrance of the CO motion cannot be reconciled with common expectations of a homogeneous, thermally activated jumplike reorientation process, but is well accounted for in a model of orientational pinning due to asymmetric distortions of the cage potential. © 2000 American Institute of Physics.
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76.60.-k Nuclear magnetic resonance and relaxation
36.40.Mr Spectroscopy and geometrical structure of clusters
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back to top Theoretical Methods and Algorithms

Accurately solving the electronic Schrödinger equation of atoms and molecules by extrapolating to the basis set limit. I. The helium dimer (He2)

Robert J. Gdanitz

J. Chem. Phys. 113, 5145 (2000); http://dx.doi.org/10.1063/1.1290001 (9 pages) | Cited 52 times

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A new formula, EL−E∝(L+3/4)−3, to extrapolate energies, EL (that arise when the basis set is truncated at a finite angular momentum quantum number, L) to the limit, E, is derived and applied to the computation of the pair potential of He. Large basis sets up to d-aug-cc-pV5Z and -6Z are used, and in addition, a new cc-pV7Z set is presented. The full-CI is approximated using the “multireference averaged coupled-pair functional” (MR-ACPF) with 121 references. The calculated molecular constants of He2 are in excellent agreement with those recently obtained with r12-MR-ACPF [R. J. Gdanitz, Mol. Phys. 96, 1423 (1999)], but they agree only fairly with the complete-CI estimate of van Mourik and Dunning [J. Chem. Phys. 111, 9248 (1999)]. The potential of Komasa [J. Chem. Phys. 110, 7909 (1999)] which has been calculated with the “exponentially correlated Gaussians” method does not give a bound state. The sensitivity of the molecular constants 〈R〉 and D0 to errors of the interaction potential at different distances is estimated by perturbing the potential by Gaussian functions. The region of 5≲R/a0≲9 is found to be most sensitive. From this analysis, doubts arise that recent calculations (including the present one) are accurate enough to allow the molecular constants to be determined to better than ≈10%. © 2000 American Institute of Physics.
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02.60.Ed Interpolation; curve fitting
31.15.vn Electron correlation calculations for diatomic molecules
34.20.Gj Intermolecular and atom-molecule potentials and forces

CC2 excitation energy calculations on large molecules using the resolution of the identity approximation

Christof Hättig and Florian Weigend

J. Chem. Phys. 113, 5154 (2000); http://dx.doi.org/10.1063/1.1290013 (8 pages) | Cited 280 times

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A new implementation of the approximate coupled cluster singles and doubles method CC2 is reported, which is suitable for large scale integral-direct calculations. It employs the resolution of the identity (RI) approximation for two-electron integrals to reduce the CPU time needed for calculation and I/O of these integrals. We use a partitioned form of the CC2 equations which eliminates the need to store double excitation cluster amplitudes. In combination with the RI approximation this formulation of the CC2 equations leads to a reduced scaling of memory and disk space requirements with the number of correlated electrons (n) and basis functions (N) to, respectively, O(N2) and O(nN2), compared to O(n2N2) in previous implementations. The reduced CPU, memory and disk space requirements make it possible to perform CC2 calculations with accurate basis sets on large molecules, which would not be accessible with conventional implementations of the CC2 method. We present an application to vertical excitation energies of alkenes C2nH2n+2, for n = 1–12, and report results for the lowest lying dipole-allowed transitions for the TZVPP basis sets, which for n = 12 contain 1108 basis functions. Comparison with conventional CC2 results for the smaller alkenes show that for CC2 ground state energies and for excitation energies of valence states, the error due to the RI approximation is negligible compared to the usual basis set error, if auxiliary basis sets are used, which have been optimized for MP2 energy calculations. © 2000 American Institute of Physics.
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31.15.bw Coupled-cluster theory
02.70.-c Computational techniques; simulations

Structural decomposition of the chemical shielding tensor: Contributions to the asymmetry, anisotropy, and orientation

Judith Herzfeld, Donald J. Olbris, Efim Furman, and Vadim Benderskiy

J. Chem. Phys. 113, 5162 (2000); http://dx.doi.org/10.1063/1.1290019 (9 pages) | Cited 2 times

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The nine elements of chemical shielding tensors contain important information about local structure, but the extraction of that information is difficult. Here we explore a semiempirical method that has the potential for providing relatively accessible structural correlations. The approach entails approximating the field-induced electron current density as entirely perpendicular to the applied field. This has two interesting consequences. (1) The resulting shielding tensor is perfectly symmetric. Thus, asymmetry in a shielding tensor is an indication of current density that is not orthogonal to the applied field. (2) The orientation dependence of the chemical shielding at a point of interest is related explicitly to the isotropic average of the chemical shielding at every point in the surrounding region. This suggests a relatively simple relationship between the orientation dependence of the chemical shielding and the molecular structure. Good correlation with experimental tensors is obtained with just one or two adjustable parameters in several series of compounds, including silicates, phosphates, hydrogen bonds, carboxyls, and amides. As expected, the results indicate that for a given center, the contribution to the shielding anisotropy that is associated with each bonded neighbor increases as the number of electrons at either the center or the neighbors increases. © 2000 American Institute of Physics.
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31.30.-i Corrections to electronic structure
33.15.Bh General molecular conformation and symmetry; stereochemistry

The quantum vibrational dynamics of Cl−(H2O)n clusters

Gregory K. Schenter, Bruce C. Garrett, and Gregory A. Voth

J. Chem. Phys. 113, 5171 (2000); http://dx.doi.org/10.1063/1.1290132 (8 pages) | Cited 19 times

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The centroid molecular dynamics technique is applied to the case of chloride–water clusters to estimate their finite temperature quantum vibrational structure. We employ the flexible RWK2 water potential [J. R. Reimers, R. O. Watts, and M. L. Klein, Chem. Phys. 64, 95 (1982)] and the parametrization of a chloride–water interaction potential of Dorsett, Watts and Xantheas [J. Phys. Chem. A 103, 3351 (1999)]. We then investigate the temperature-dependent vibrational structure (infrared spectra). We find that the centroid molecular dynamics technique is capable of recovering a majority of the red shift associated with hydrogen bonding. © 2000 American Institute of Physics.
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36.40.Mr Spectroscopy and geometrical structure of clusters
33.20.Tp Vibrational analysis
33.70.Jg Line and band widths, shapes, and shifts
33.15.Mt Rotation, vibration, and vibration-rotation constants
34.20.Gj Intermolecular and atom-molecule potentials and forces

Direct calculation of the one-electron density matrix for closed-shell systems

Osamu Matsuoka, Takaharu Matsufuji, and Tatsuji Sano

J. Chem. Phys. 113, 5179 (2000); http://dx.doi.org/10.1063/1.1290015 (6 pages)

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It has been found that independent parameters in the variation of a one-electron density matrix (DM) for closed-shell systems are elements of its unitary transformed matrix and, in a special case, reduce to the rotation parameters that connect the occupied and virtual orbital spaces in the exponential transformed self-consistent field method. To obtain the unitary matrix of transformation, a simpler method of orthogonalizing the column vectors of the DM has been proposed instead of its diagonalization. An iterative method has been formulated to determine these independent parameters. Several test calculations using this method reproduced the results using the Hartree–Fock–Roothaan method. © 2000 American Institute of Physics.
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31.15.xr Self-consistent-field methods
02.10.Ud Linear algebra
02.10.Xm Multilinear algebra
02.60.-x Numerical approximation and analysis

Kohn–Sham calculations using hybrid exchange-correlation functionals with asymptotically corrected potentials

Mark J. Allen and David J. Tozer

J. Chem. Phys. 113, 5185 (2000); http://dx.doi.org/10.1063/1.1290002 (8 pages) | Cited 16 times

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The theory is presented for asymptotically correcting the potentials of hybrid exchange-correlation functionals, i.e., those that include a fraction of orbital exchange. The Kohn–Sham equations involve a multiplicative potential due to the continuum part of the hybrid functional and a nonmultiplicative term due to the orbital exchange. In asymptotic regions the multiplicative σ-spin potential is corrected to take the form (CX−1)/r+ϵHOMO,σ+Iσ, where CX is the fraction of orbital exchange; ϵHOMO,σ is the σ-spin self-consistent highest occupied Kohn–Sham eigenvalue; and Iσ is an approximate ionization energy. For the hydrogen atom, the asymptotic correction leads to a potential that closely resembles the exact potential; the eigenvalue spectrum is intermediate between the Schrödinger and Hartree–Fock eigenvalues, reflecting the presence of orbital exchange. Kohn–Sham orbitals and eigenvalues determined from this procedure have been used to calculate singlet vertical excitation energies for CO, N2, H2CO, C2H4, and C6H6. The correction significantly improves excitation energies to Rydberg states, with mean absolute errors below 0.2 eV. However, despite including orbital exchange, the results do not represent an improvement over the results obtained by asymptotically correcting a recently developed GGA functional. The asymptotic correction is also shown to reduce static isotropic polarizabilities. © 2000 American Institute of Physics.
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31.15.E- Density-functional theory
34.20.Gj Intermolecular and atom-molecule potentials and forces
02.10.Ud Linear algebra
02.10.Xm Multilinear algebra
31.15.V- Electron correlation calculations for atoms, ions and molecules
31.50.Df Potential energy surfaces for excited electronic states
32.30.-r Atomic spectra
33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility

Quaternion formulation of diffusion quantum Monte Carlo for the rotation of rigid molecules in clusters

David M. Benoit and David C. Clary

J. Chem. Phys. 113, 5193 (2000); http://dx.doi.org/10.1063/1.1288788 (10 pages) | Cited 9 times

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A quaternion formulation is used to derive an algorithm for performing calculations on molecular clusters using the quantum diffusion Monte Carlo method. It is assumed that the monomers in the cluster rotate and translate as rigid bodies. The algorithm is tested on the water dimer and the benzene–water cluster. Comparison with dissociation energies and rotational constants obtained with other methods illustrates the accuracy of the algorithm. © 2000 American Institute of Physics.
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36.40.Mr Spectroscopy and geometrical structure of clusters
33.15.Fm Bond strengths, dissociation energies
33.15.Mt Rotation, vibration, and vibration-rotation constants
05.10.Ln Monte Carlo methods
02.70.Rr General statistical methods
03.65.Ge Solutions of wave equations: bound states

Determination of vibrational polarizabilities and hyperpolarizabilities using field-induced coordinates

Josep M. Luis, Miquel Duran, Benoît Champagne, and Bernard Kirtman

J. Chem. Phys. 113, 5203 (2000); http://dx.doi.org/10.1063/1.1290022 (11 pages) | Cited 25 times

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An analytical set of field-induced coordinates (FICs) is defined. It is shown that, instead of 3N−6 normal coordinates, a relatively small number of FICs is sufficient to describe the vibrational polarizability and hyperpolarizabilities due to nuclear relaxation. The fact that the number of FICs does not depend upon the size of the molecule leads to computational advantages. A method is provided for separating anharmonic contributions from harmonic contributions as well as effective mechanical from electrical anharmonicity. Hartree–Fock calculations on a dozen representative conjugated molecules illustrate the procedures and indicate that anharmonicity can be very important. Other potential applications including the determination of zero-point vibrational averaging corrections are noted. © 2000 American Institute of Physics.
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33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility
31.15.xr Self-consistent-field methods
31.15.A- Ab initio calculations
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.20.Tp Vibrational analysis
33.15.Bh General molecular conformation and symmetry; stereochemistry
42.65.An Optical susceptibility, hyperpolarizability

Fourier grid Hamiltonian multiconfigurational self-consistent-field: A method to calculate multidimensional hydrogen vibrational wavefunctions

Simon P. Webb and Sharon Hammes-Schiffer

J. Chem. Phys. 113, 5214 (2000); http://dx.doi.org/10.1063/1.1289528 (14 pages) | Cited 30 times

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The Fourier Grid Hamiltonian Multiconfigurational Self-Consistent-Field (FGH-MCSCF) method for calculating vibrational wavefunctions is presented. This method is designed to calculate multidimensional hydrogen nuclear wavefunctions for use in mixed quantum/classical molecular dynamics simulations of hydrogen transfer reactions. The FGH-MCSCF approach combines a MCSCF variational method, which describes the vibrational wavefunctions as linear combinations of configurations that are products of one-dimensional wavefunctions, with a Fourier grid method that represents the one-dimensional wavefunctions directly on a grid. In this method a full configuration interaction calculation is carried out in a truncated one-dimensional wavefunction space [analogous to complete active space self-consistent-field (CASSCF) in electronic structure theory]. A state-averaged approach is implemented to obtain a set of orthogonal multidimensional vibrational wavefunctions. The advantages of the FGH-MCSCF method are that it eliminates the costly calculation of multidimensional integrals, treats the entire range of the hydrogen coordinates without bias, avoids the expensive diagonalization of large matrices, and accurately describes ground and excited state hydrogen vibrational wavefunctions. This paper presents the derivation of the FGH-MCSCF method, as well as a series of test calculations on systems comparing its performance with exact diagonalization schemes. © 2000 American Institute of Physics.
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82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)
82.20.-w Chemical kinetics and dynamics
back to top Gas Phase Dynamics and Structure: Spectroscopy, Molecular Interactions, Scattering, and Photochemistry

Large amplitude vibrations in the X 2A1 state of C2B

C. Léonard, G. Chambaud, P. Rosmus, S. Carter, N. C. Handy, M. Wyss, and J. P. Maier

J. Chem. Phys. 113, 5228 (2000); http://dx.doi.org/10.1063/1.1290011 (7 pages) | Cited 5 times

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A three-dimensional potential energy function (PEF) of the 2A1 electronic ground state of C2B has been generated by electronic structure calculations. The PEF possesses a minimum in an isosceles triangular structure which lies 2204 cm−1 below two equivalent minima having linear equilibrium geometry. The barrier height between the minima relative to the triangular structure has been calculated to the 2383 cm−1. The nuclear motion problem has been solved variationally in Jacobi coordinates for J = 0 and 1. Ten vibrational states of A1 and nine of B2 symmetry are calculated to lie below the linear minima. The permutational splitting between the (000)+ and (000)− states in the linear 12C2 11B has been calculated to be 0.064 cm−1, in 12C13C11B this is 0.530 cm−1. Above the energy of the barrier to linearity there are large amplitude vibrations with triangular structure character. In the dense stack of such states vibrational modes of the linear structure are discernible, including their permutational splittings. © 2000 American Institute of Physics.
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33.20.Tp Vibrational analysis
34.20.Gj Intermolecular and atom-molecule potentials and forces
33.15.Bh General molecular conformation and symmetry; stereochemistry
31.15.bw Coupled-cluster theory
33.15.Mt Rotation, vibration, and vibration-rotation constants

Evidence for 1La fluorescence from jet-cooled 3-methylindole-polar solvent complexes

Kurt W. Short and Patrik R. Callis

J. Chem. Phys. 113, 5235 (2000); http://dx.doi.org/10.1063/1.1290030 (10 pages) | Cited 15 times

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The ratio of nonresonant two-photon induced fluorescence excitation spectra using circularly and linearly polarized light for jet-cooled 3-methylindole complexed with a series of increasingly basic hydrogen bond acceptors (water, methanol, ethanol, diethylether, diethylamine and triethylamine) is consistent with an avoided crossing of the two lowest excited singlet states, 1La and 1Lb. The dispersed fluorescence of these from this series also reflects the crossing, providing a definitive 1La jet-cooled fluorescence spectrum. The jet-cooled 1La fluorescence spectrum is not broad and redshifted, but has vibronic structure that agrees well with ab initio predictions and is similar to that of 3La phosphorescence. © 2000 American Institute of Physics.
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33.50.Dq Fluorescence and phosphorescence spectra
33.80.Rv Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states)
33.80.Be Level crossing and optical pumping
33.70.Jg Line and band widths, shapes, and shifts

Electronic excitation and ionization spectra of cyclopentadiene: Revisit by the symmetry-adapted cluster–configuration interaction method

Jian Wan, Masahiro Ehara, Masahiko Hada, and Hiroshi Nakatsuji

J. Chem. Phys. 113, 5245 (2000); http://dx.doi.org/10.1063/1.1290004 (8 pages) | Cited 15 times

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Electronic excitation and ionization spectra of cyclopentadiene (CP) were reinvestigated by the symmetry-adapted cluster (SAC) and SAC–configuration interaction (SAC-CI) method with an extended basis set and a wide active orbital space. To give a satisfactory interpretation of the general profile of the observed excitation spectrum, 40 low-lying excited singlet and triplet states (with excitation energies of up to 9.5 eV) were computed. The calculated excitation energies were greatly improved compared to those reported previously. All of the peaks in the experimental spectrum were reassigned theoretically with small deviations. The natures of the low-lying valence and Rydberg-excited states were discussed in detail, and the results were also compared with those of some other recent theoretical studies. The ionization energies calculated by the SAC-CI general-R method agree well with the experimental peaks in the photoelectron spectrum. A number of two-electron shake-up states were calculated below 23 eV. © 2000 American Institute of Physics.
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33.20.Lg Ultraviolet spectra
34.80.-i Electron and positron scattering
33.60.+q Photoelectron spectra
31.15.vq Electron correlation calculations for polyatomic molecules

Theoretical characterization of the structures and properties of phenol-(H2O)2 complexes

Wei-Hai Fang and Ruo-Zhuang Liu

J. Chem. Phys. 113, 5253 (2000); http://dx.doi.org/10.1063/1.1290017 (6 pages) | Cited 4 times

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Extensive ab initio calculations at different levels of theory have been performed with the 6-31G(d,p) basis set. Three minimum energy structures of (a), (b), and (c) were found on the ground (S0) and excited (S1) state surfaces of the phenol–(H2O)2 complex, with cyclic structure (a) being the most stable. Experimentally inferred very low frequencies for intermolecular vibrations in S1 were reproduced using the present calculations. The high vibrational mode density resulting from very low frequency vibrations of the structure (b) may be responsible for a broad electronic origin in the spectra of the phenol–(H2O)2 complex. The intermolecular interaction has little influence on the structures of phenol and water, but a significant change is found in the properties upon complexation. The intramolecular vibrations, which have frequencies of the magnitude of the intermolecular vibrations or involve the OH group of phenol, are significantly affected by formation of complex. All of these have been discussed in detail. © 2000 American Institute of Physics.
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31.50.Df Potential energy surfaces for excited electronic states
31.15.A- Ab initio calculations
36.40.Mr Spectroscopy and geometrical structure of clusters
33.15.Bh General molecular conformation and symmetry; stereochemistry
33.20.Tp Vibrational analysis
33.15.Mt Rotation, vibration, and vibration-rotation constants
34.50.Ez Rotational and vibrational energy transfer
31.15.xr Self-consistent-field methods

Comparative ab initio study of the structures, energetics and spectra of X−⋅(H2O)n = 1–4 [X=F, Cl, Br, I] clusters

Jongseob Kim, Han Myoung Lee, Seung Bum Suh, D. Majumdar, and Kwang S. Kim

J. Chem. Phys. 113, 5259 (2000); http://dx.doi.org/10.1063/1.1290016 (14 pages) | Cited 91 times

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X−⋅(H2O)n = 1–4 [X=F, Cl, Br, I] have been studied using high level ab initio calculations. This extensive work compares the structures of the different halide water clusters and has found that the predicted minimum energy geometries for different cluster are accompanied by several other structures close to these global minima. Hence the most highly populated structures can change depending on temperature due to the entropy effect. As the potential surfaces are flat, the wide-ranging zero point vibrational effects are important at 0 K, and not only a number of low-lying energy conformers but also large amplitude motions can be important in determining structures, energies, and spectra at finite temperatures. The binding energies, ionization potentials, charge-transfer-to-solvent (CTTS) energies, and the O–H stretching frequencies are reported, and compared with the experimental data available. A distinctive difference between F−⋅(H2O)n and X−⋅(H2O)n (X=Cl, Br, I) is noted, as the former tends to favor internal structures with negligible hydrogen bonding between water molecules, while the latter favors surface structures with significant hydrogen bonding between water molecules. These characteristics are well featured in their O–H spectra of the clusters. However, the spectra are forced to be very sensitive to the temperature, which explains some differences between different spectra. In case of F−⋅(H2O)n, a significant charge transfer is noted in the S0 ground state, which results in much less significant charge transfer in the S1 excited state compared with other hydrated halide clusters which show near full charge transfers in the S1 excited states. Finally, the nature of the stabilization interactions operative in these clusters has been explained in terms of many-body interaction energies. © 2000 American Institute of Physics.
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36.40.Mr Spectroscopy and geometrical structure of clusters
36.40.Cg Electronic and magnetic properties of clusters
36.40.Wa Charged clusters
31.15.A- Ab initio calculations
33.15.Ry Ionization potentials, electron affinities, molecular core binding energy
33.15.Bh General molecular conformation and symmetry; stereochemistry
34.70.+e Charge transfer
31.50.Df Potential energy surfaces for excited electronic states

Vibrational spectra and electron detachment energy of the anionic water hexamer

Seung Bum Suh, Han Myoung Lee, Jongseob Kim, Jin Yong Lee, and Kwang S. Kim

J. Chem. Phys. 113, 5273 (2000); http://dx.doi.org/10.1063/1.1290018 (5 pages) | Cited 38 times

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A number of experimental and theoretical studies have been carried out on the anionic water hexamer in the last decade. However, none of these studies have reported the adiabatic electron detachment energy. The present study employing extensive high-level ab initio calculations report the adiabatic electron detachment energy, which explains the unusual stability of the anionic water hexamer. This stability can be correlated to the unusually intense peak observed in the photoelectron-detachment spectra. It is also shown that our previously predicted pyramid structure reproduces the important characteristics of the experimental O–H vibrational spectra. © 2000 American Institute of Physics.
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36.40.Mr Spectroscopy and geometrical structure of clusters
36.40.Cg Electronic and magnetic properties of clusters
33.80.Eh Autoionization, photoionization, and photodetachment
34.50.Gb Electronic excitation and ionization of molecules
31.15.A- Ab initio calculations
33.15.Mt Rotation, vibration, and vibration-rotation constants

Rotational spectroscopy of H3P⋯BrCl and the systematics of intermolecular electron transfer in the series B⋯BrCl, where B=CO, HCN, H2O, C2H2, C2H4, H2S, NH3, and PH3

A. C. Legon, J. M. A. Thumwood, and E. R. Waclawik

J. Chem. Phys. 113, 5278 (2000); http://dx.doi.org/10.1063/1.1290031 (9 pages) | Cited 8 times

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Ground-state rotational spectra of the isotopomers H3P⋯79Br35Cl, H3P⋯81Br35Cl, H3P⋯79Br37Cl, H3P⋯81Br37Cl, D3P⋯79Br35Cl, and D3P⋯81Br35Cl, of the phosphine–bromine monochloride complex were observed by the pulsed-jet, Fourier-transform method, incorporating a mixing nozzle to preclude reaction among the component gases. Each isotopomer exhibited a symmetric-top-type spectrum which yielded accurate values of the spectroscopic constants B0, DJ, DJK, χaa (Br), χaa (Cl), Maa (Br), and Mbb (Br) on analysis. Interpretations of the changes in the B0 values with isotopomer showed that the intermolecular bond involves P and Br, with r(P⋯Br)=2.869(1) Å and that the BrCl bond increases in length by ∼0.04 Å on complex formation. Changes in the halogen nuclear quadrupole coupling constants when H3P⋯BrCl is formed lead, with the aid of the Townes–Dailey model, to the conclusion that a fraction δi = 0.100(5) of an electron is transferred from P to Br on complex formation, while the polarization of BrCl by PH3 can be viewed as the transfer of 0.128(2)e from Br to Cl, leading to a net change of −0.028(5)e in the population of the 4pz orbital of Br. The complex is only of moderate strength, with an intermolecular stretching force constant kσ = 11.5 Nm−1. Values of δi, similarly determined, for the series B⋯BrCl, where B=CO, HCN, H2O, C2H2, C2H4, H2S, NH3, or PH3, are presented. It is shown that the variation of δi with the ionization energy IB of the Lewis base B can be described by an expression δi = Aexp(−bIB). This behavior is compared with that for the corresponding series B⋯ICl. © 2000 American Institute of Physics.
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33.20.Bx Radio-frequency and microwave spectra
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.15.Ry Ionization potentials, electron affinities, molecular core binding energy
33.20.Sn Rotational analysis
33.25.+k Nuclear resonance and relaxation
33.70.Jg Line and band widths, shapes, and shifts

Multiple dynamical pathways in the O(1D)+CH4 reaction: A comprehensive crossed beam study

J. J. Lin, J. Shu, Y. T. Lee, and X. Yang

J. Chem. Phys. 113, 5287 (2000); http://dx.doi.org/10.1063/1.1289462 (15 pages) | Cited 35 times

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In this report, the O(1D)+CH4 reaction has been reinvestigated using universal crossed molecular beam methods. Angular resolved time-of-flight spectra have been measured for various reaction channels of the title reaction: OH+CH3, H+H2COH/H3CO, and H2+HCOH/H2CO. Different product angular distributions have been observed for these product channels, indicating that these reaction channels occur via distinctive dynamical pathways. This study provides an excellent example of multiple dynamical pathways in a single chemical reaction, which opens enormous opportunities in investigating the dynamics of complicated chemical reactions that are important in combustion and atmospheric chemistry, and also provides a link between kinetics studies and dynamical research. © 2000 American Institute of Physics.
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82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
82.33.Tb Atmospheric chemistry
34.50.Lf Chemical reactions
82.20.Hf Product distribution
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment
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