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7 Aug 2006

Volume 125, Issue 5, Articles (05xxxx)

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Experimental evidence of dynamic trapping in the scattering of H2 from Pd(110)

D. Barredo, G. Laurent, C. Díaz, P. Nieto, H. F. Busnengo, A. Salin, D. Farías, and F. Martín

J. Chem. Phys. 125, 051101 (2006); http://dx.doi.org/10.1063/1.2229203 (4 pages) | Cited 5 times

Online Publication Date: 7 August 2006

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We have performed H2(D2) diffraction experiments on a Pd(110) surface using two different high-sensitivity set-ups. We have found that, although the total reflectivity of Pd(110) is comparable to that observed in other reactive systems, the corresponding H2(D2) diffraction patterns are quite different: no diffraction peak, including the specular one, is observed on Pd(110). This unexpected result is the consequence of dynamic trapping. Such interpretation is supported by classical dynamics calculations based on accurate ab initio potential energy surfaces.
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34.35.+a Interactions of atoms and molecules with surfaces
34.20.-b Interatomic and intermolecular potentials and forces, potential energy surfaces for collisions
31.15.A- Ab initio calculations
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back to top Theoretical Methods and Algorithms

Optimized effective potential from a correlated wave function: Optimized effective potential-generalized valence bond (OEP-GVB)

Richard P. Muller and Michael P. Desjarlais

J. Chem. Phys. 125, 054101 (2006); http://dx.doi.org/10.1063/1.2216701 (5 pages) | Cited 6 times

Online Publication Date: 1 August 2006

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The optimized effective potential (OEP) method allows orbital-dependent functionals to be used in density functional theory. Traditionally the orbital-dependent functional of interest has been the Hartree-Fock energy, leading to exact exchange density functional theory. Here we present results that use a generalized valence-bond (GVB) wave function, a multiconfigurational wave function that includes static correlation and dissociates to the proper limits. We demonstrate the effectiveness of the OEP-GVB method by showing the dissociation of H2 and the excitation spectrum of He.
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31.15.xw Valence bond calculations
31.15.xr Self-consistent-field methods
31.15.E- Density-functional theory
31.15.vj Electron correlation calculations for atoms and ions: excited states
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
82.20.Db Transition state theory and statistical theories of rate constants

Coordinate transformation methods to calculate state-to-state reaction probabilities with wave packet treatments

Susana Gómez-Carrasco and Octavio Roncero

J. Chem. Phys. 125, 054102 (2006); http://dx.doi.org/10.1063/1.2218337 (14 pages) | Cited 26 times

Online Publication Date: 1 August 2006

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A procedure for the transformation from reactant to product Jacobi coordinates is proposed, which is designed for the extraction of state-to-state reaction probabilities using a time-dependent method in a body-fixed frame. The method consists of several steps which involve a negligible extra computational time as compared with the propagation. Several intermediate coordinates are used, in which the efficiency depends on the masses of the atoms involved in the reaction. A detailed study of the relative efficiency of using reactant and product Jacobi coordinates is presented for several systems, and simple arguments are found depending on the masses of the atoms involved in the reaction. It is found that the proposed method is, in general, more efficient than the use of product Jacobi coordinates, specially for nonzero total angular momentum. State-to-state reaction probabilities are obtained for Li+FH→LiF+H and F+HO→FH+O collisions for several total angular momenta.
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82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
82.20.Rp State to state energy transfer

A state-specific polarizable continuum model time dependent density functional theory method for excited state calculations in solution

Roberto Improta, Vincenzo Barone, Giovanni Scalmani, and Michael J. Frisch

J. Chem. Phys. 125, 054103 (2006); http://dx.doi.org/10.1063/1.2222364 (9 pages) | Cited 51 times

Online Publication Date: 2 August 2006

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An effective state specific (SS) model for the inclusion of solvent effects in time dependent density functional theory (TD-DFT) computations of excited electronic states has been developed and coded in the framework of the so-called polarizable continuum model (PCM). Different relaxation time regimes can be treated thus giving access to a number of different spectroscopic properties together with solvent relaxation energies of paramount relevance in electron transfer processes. SS and conventional linear response (LR) models have been compared for two benchmark systems (coumarin 153 and formaldehyde in different solvents) and in the limiting simple case of a dipolar solute embedded in a spherical cavity. The results point out the complementarity of LR and SS approaches and the advantages of the latter model especially for polar solvents. The favorable scaling properties of PCM-TD-DFT models in both SS and LR variants and their availability in effective quantum mechanical codes pave the route for the computation of reliable spectroscopic properties of large molecules of technological and/or biological interest in their natural environments.
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31.50.Df Potential energy surfaces for excited electronic states
31.70.Dk Environmental and solvent effects
31.15.E- Density-functional theory

Statistical estimates of electron correlations

W. Győrffy, Thomas M. Henderson, and J. C. Greer

J. Chem. Phys. 125, 054104 (2006); http://dx.doi.org/10.1063/1.2236115 (4 pages) | Cited 2 times

Online Publication Date: 2 August 2006

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While arbitrarily accurate solutions to the many-body Schrödinger equation are possible through a brute force expansion of the wave function, the length of the expansions required renders the approach intractable except for few-electron problems. By considering the form of the energy resulting from truncation of the many-particle expansion space, it is shown that accurate determination of electron correlations may be extracted from estimates of average or effective energy contributions while maintaining a reduced dimension for the expansion space. An energy formula expressed as a rational function of the expansion vector length is determined, allowing for estimates of asymptotic limits of many-body correlations.
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31.15.V- Electron correlation calculations for atoms, ions and molecules
03.65.Ge Solutions of wave equations: bound states

A proof of Jarzynski’s nonequilibrium work theorem for dynamical systems that conserve the canonical distribution

E. Schöll-Paschinger and C. Dellago

J. Chem. Phys. 125, 054105 (2006); http://dx.doi.org/10.1063/1.2227025 (5 pages) | Cited 21 times

Online Publication Date: 3 August 2006

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We present a derivation of the Jarzynski [Phys. Rev. Lett. 78, 2690 (1997)] identity and the Crooks [J. Stat. Phys. 90, 1481 (1998)] fluctuation theorem for systems governed by deterministic dynamics that conserves the canonical distribution such as Hamiltonian dynamics, Nosé-Hoover dynamics, Nosé-Hoover chains, and Gaussian isokinetic dynamics. The proof is based on a relation between the heat absorbed by the system during the nonequilibrium process and the Jacobian of the phase flow generated by the dynamics.
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05.70.Ln Nonequilibrium and irreversible thermodynamics
05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion

Gaussian-type function set without prolapse for the Dirac-Fock-Roothaan equation (II): math through math

Shigeyoshi Yamamoto, Hiroshi Tatewaki, and Yoshihiro Watanabe

J. Chem. Phys. 125, 054106 (2006); http://dx.doi.org/10.1063/1.2222362 (5 pages) | Cited 3 times

Online Publication Date: 3 August 2006

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We present prolapse-free universal Gaussian-type basis sets for math through math. The basis set is determined so that the Dirac-Fock-Roothaan total energy should decrease monotonically toward the numerical Dirac-Fock total energy. The difference between the Dirac-Fock-Roothaan total energy and the numerical Dirac-Fock total energy is less than 3×10−6 hartree for math through math, and less than 5×10−6 hartree for math. The exponents of the present sets are determined in an even-tempered manner, aiming to give total energy closer to the numerical Dirac-Fock value as the expansion term increases. The recommended set is expanded by (64, 64, 64, 46, 46, 46, 46) terms for (s+, p−, p+, d−, d+, f−, f+) symmetries, respectively. A practical set with (56, 48, 48, 36, 36, 36, 36) terms is also presented.
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31.30.J- Relativistic and quantum electrodynamic (QED) effects in atoms, molecules, and ions
31.15.xr Self-consistent-field methods

Nonlinear effects in the interaction of time-dependent fields and chiral systems: A computational investigation

Angelika Baranowska, Antonio Rizzo, Branislav Jansík, and Sonia Coriani

J. Chem. Phys. 125, 054107 (2006); http://dx.doi.org/10.1063/1.2222349 (10 pages) | Cited 3 times

Online Publication Date: 4 August 2006

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The nonlinear changes induced in the refractive index and in the optical rotatory dispersion when radiation interacts with a chiral system are studied computationally. The molecular parameters describing these effects are determined for methyloxirane, employing Hartree-Fock and density functional frequency dependent analytical response theory, the latter with the use of Becke three-parameter Lee-Yang-Parr functional. Their contribution to several circular and axial birefringences, which could be observed in pump-and-probe experiments for various combinations of polarization status and propagation direction of the two beams, is ascertained.
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33.55.+b Optical activity and dichroism
42.65.-k Nonlinear optics
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
31.15.xr Self-consistent-field methods
31.15.E- Density-functional theory

Obtaining reaction coordinates by likelihood maximization

Baron Peters and Bernhardt L. Trout

J. Chem. Phys. 125, 054108 (2006); http://dx.doi.org/10.1063/1.2234477 (10 pages) | Cited 43 times

Online Publication Date: 4 August 2006

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We present a new approach for calculating reaction coordinates in complex systems. The new method is based on transition path sampling and likelihood maximization. It requires fewer trajectories than a single iteration of existing procedures, and it applies to both low and high friction dynamics. The new method screens a set of candidate collective variables for a good reaction coordinate that depends on a few relevant variables. The Bayesian information criterion determines whether additional variables significantly improve the reaction coordinate. Additionally, we present an advantageous transition path sampling algorithm and an algorithm to generate the most likely transition path in the space of collective variables. The method is demonstrated on two systems: a bistable model potential energy surface and nucleation in the Ising model. For the Ising model of nucleation, we quantify for the first time the role of nuclei surface area in the nucleation reaction coordinate. Surprisingly, increased surface area increases the stability of nuclei in two dimensions but decreases nuclei stability in three dimensions.
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82.20.Db Transition state theory and statistical theories of rate constants
82.20.Kh Potential energy surfaces for chemical reactions
82.60.Nh Thermodynamics of nucleation

Hybrid correlation models based on active-space partitioning: Seeking accurate O(N5) ab initio methods for bond breaking

Arteum D. Bochevarov, Berhane Temelso, and C. David Sherrill

J. Chem. Phys. 125, 054109 (2006); http://dx.doi.org/10.1063/1.2222350 (10 pages) | Cited 1 time

Online Publication Date: 4 August 2006

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Møller-Plesset second-order (MP2) perturbation theory remains the least expensive standard ab initio method that includes electron correlation, scaling as O(N5) with the number of molecular orbitals N. Unfortunately, when restricted Hartree-Fock orbitals are employed, the potential energy curves calculated with this method are of little use at large interatomic separations because of the divergent behavior of MP2 in these regions. In our previous study [ J. Chem. Phys. 122, 234110 (2005) ] we combined the MP2 method with the singles and doubles coupled cluster (CCSD) method to produce a hybrid method that retains the computational scaling of MP2 and improves dramatically the shape of the MP2 curves. In this work we expand the hybrid methodology to several other schemes. We investigate a new, improved MP2-CCSD method as well as a few other O(N5) methods related to the Epstein-Nesbet pair correlation theory. Nonparallelity errors across the dissociation curve as well as several spectroscopic constants are computed for BH, HF, H2O, CH+, CH4, and Li2 molecules with the 6-31G* basis set and compared with the corresponding full configuration interaction results. We show that among the O(N5) methods considered, our new hybrid MP2-CCSD method is the most accurate and significantly outperforms MP2 not only at large interatomic separations, but also near equilibrium geometries.
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31.15.A- Ab initio calculations
31.15.xp Perturbation theory
31.15.bw Coupled-cluster theory
31.50.-x Potential energy surfaces
31.15.vn Electron correlation calculations for diatomic molecules
31.15.vq Electron correlation calculations for polyatomic molecules

Calculation of zero-field splitting parameters: Comparison of a two-component noncolinear spin-density-functional method and a one-component perturbational approach

Roman Reviakine, Alexei V. Arbuznikov, Jean-Christophe Tremblay, Christian Remenyi, Olga L. Malkina, Vladimir G. Malkin, and Martin Kaupp

J. Chem. Phys. 125, 054110 (2006); http://dx.doi.org/10.1063/1.2227382 (12 pages) | Cited 20 times

Online Publication Date: 4 August 2006

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Two different sets of approaches for the density-functional calculation of the spin-orbit contributions to zero-field splitting (ZFS) parameters of high-spin systems have been implemented within the same quantum chemistry code ReSpect and have been validated and compared for a series of model systems. The first approach includes spin-orbit coupling variationally in a two-component calculation, using either an all-electron Douglas-Kroll-Hess ansatz or two-component relativistic pseudopotentials. The ZFS parameters are computed directly from energy differences between different relativistic states. Additionally, an approximate second-order perturbation theory approach has been implemented, based on nonrelativistic or scalar relativistic wave functions. For a series of group 16 triplet diatomics and for the octet GdH3 molecules, two-component density functional calculations underestimate the zero-field splitting D systematically by a factor of 2. This may be rationalized readily by the incomplete description of states with ∣MJ∣<J by a single-determinantal wave function built from two-component spinors. In the case of two 3d transition metal complexes and for GdH3, the results depend furthermore sensitively on exchange-correlation functional. Results of the alternative one-component approach agree strikingly with the two-component data for systems with small spin-orbit effects and start to deviate from them only for heavier systems with large spin-orbit effects. These results have fundamental implications for the achievable accuracy of one-component density-functional approaches used widely to compute ZFS parameters in the field of molecular magnetism. Possible refinements of both one-and two-component approaches are discussed.
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31.30.Gs Hyperfine interactions and isotope effects
33.20.Wr Vibronic, rovibronic, and rotation-electron-spin interactions
31.15.E- Density-functional theory
31.15.xp Perturbation theory
31.30.J- Relativistic and quantum electrodynamic (QED) effects in atoms, molecules, and ions
back to top Gas Phase Dynamics and Structure: Spectroscopy, Molecular Interactions, Scattering, and Photochemistry

Total dissociative electron attachment cross sections for molecular constituents of DNA

K. Aflatooni, A. M. Scheer, and P. D. Burrow

J. Chem. Phys. 125, 054301 (2006); http://dx.doi.org/10.1063/1.2229209 (5 pages) | Cited 44 times

Online Publication Date: 1 August 2006

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Total cross sections for the dissociative electron attachment process are presented for the DNA bases thymine, cytosine, and adenine and for three compounds used as surrogates for the ribose and phosphate groups, tetrahydrofuran, 3-hydroxytetrahydrofuran, and trimethylphosphate, respectively. Cross section magnitudes are obtained by observation of positive ion production and normalization to ionization cross sections calculated elsewhere using the binary-encounter-Bethe method. The average cross section of the three bases is 3–10 times smaller than the effective cross section per nucleotide reported for single strand breaks in surface-bound supercoiled DNA. Consequently, damage to the bases alone does not appear to account for the major portion of the strand breaks. The presence of an OH group on the ribose surrogate considerably enhances its cross section. Model compounds in which protonation or OH groups are used to terminate bonds may therefore display larger cross sections than in DNA itself.
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87.14.G- Nucleic acids
82.39.Pj Nucleic acids, DNA and RNA bases
34.80.Lx Recombination, attachment, and positronium formation
34.50.Fa Electronic excitation and ionization of atoms (including beam-foil excitation and ionization)

Combustion-generated nanoparticles produced in a benzene flame: A multiscale approach

Angela Violi and Arun Venkatnathan

J. Chem. Phys. 125, 054302 (2006); http://dx.doi.org/10.1063/1.2234481 (8 pages) | Cited 10 times

Online Publication Date: 1 August 2006

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This paper details the multiscale methodology developed to analyze the formation of nanoparticles in a manner that makes it possible to follow the evolution of the structures in a chemically specific way. The atomistic model for particle inception code that combines the strengths of kinetic Monte Carlo and molecular dynamics is used to study the chemical and physical properties of nanoparticles generated in a premixed fuel-rich benzene flame, providing atomistic scale structures (bonds, bond angles, dihedral angles) as soot precursors evolve into a three-dimensional structure. Morphology, density, porosity, and other physical properties are computed. Two heights corresponding to two different times in the benzene flame, experimentally studied by Bittner and Howard [ Proc. Combust. Inst. 18, 1105 (1981) ], were chosen to examine the influence of different environments on structural properties of the particles formed.
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61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
61.43.Bn Structural modeling: serial-addition models, computer simulation
82.33.Vx Reactions in flames, combustion, and explosions

High-resolution infrared studies in slit supersonic discharges: CH2 stretch excitation of jet-cooled CH2Cl radical

Erin S. Whitney, Thomas Haeber, Michael D. Schuder, Andrew C. Blair, and David J. Nesbitt

J. Chem. Phys. 125, 054303 (2006); http://dx.doi.org/10.1063/1.2208612 (10 pages) | Cited 5 times

Online Publication Date: 2 August 2006

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First high-resolution infrared spectra are presented for jet-cooled CH2 math and CH2 math radicals in the symmetric (ν1) CH2 stretching mode. A detailed spectral assignment yields refined lower and upper state rotational constants, as well as fine structure spin-rotation parameters from least-squares fits to the sub-Doppler line shapes for individual transitions. The rotational constants are consistent with a nearly planar structure, but do not exclude substantial large amplitude bending motion over a small barrier to planarity accessible with zero-point excitation. High level coupled cluster (singles/doubles/triples) calculations, extrapolated to the complete basis set limit, predict a slightly nonplanar equilibrium structure (θ ∼ 11°), with a vibrationally adiabatic treatment of the bend coordinate yielding a v = 1←0 anharmonic frequency (393 cm−1) in excellent agreement with matrix studies (νbend ∼ 400 cm−1). The antisymmetric CH2 stretch vibration is not observed despite high sensitivity detection (signal to noise ratio >20:1) in the symmetric stretch band. This is consistent with density functional theory intensity calculations indicating a >35-fold smaller antisymmetric stretch transition moment for CH2Cl, and yet contrasts dramatically with high-resolution infrared studies of CH2F radical, for which both symmetric and antisymmetric CH2 stretches are observed in a nearly 2:1 intensity ratio. A simple physical model is presented based on a competition between bond-dipole and “charge-sloshing” contributions to the transition moment, which nicely explains the trends in CH2X symmetric versus asymmetric stretch intensities as a function of electron withdrawing group (X = D,Br,Cl,F).
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33.20.Ea Infrared spectra
33.15.Mt Rotation, vibration, and vibration-rotation constants
31.15.bw Coupled-cluster theory
33.15.Bh General molecular conformation and symmetry; stereochemistry
31.15.E- Density-functional theory

Jet-cooled infrared spectroscopy in slit supersonic discharges: Symmetric and antisymmetric CH2 stretching modes of fluoromethyl (CH2F) radical

Erin S. Whitney, Feng Dong, and David J. Nesbitt

J. Chem. Phys. 125, 054304 (2006); http://dx.doi.org/10.1063/1.2208613 (12 pages) | Cited 3 times

Online Publication Date: 2 August 2006

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The combination of shot noise-limited direct absorption spectroscopy with long-path-length slit supersonic discharges has been used to obtain first high-resolution infrared spectra for jet-cooled CH2F radicals in the symmetric (ν1) and antisymmetric (ν5) CH2 stretching modes. Spectral assignment has yielded refined lower- and upper-state rotational constants and fine-structure parameters from least-squares fits to the sub-Doppler line shapes for individual transitions. The rotational constants provide indications of large amplitude vibrational averaging over a low-barrier double minimum inversion-bending potential. This behavior is confirmed by high-level coupled cluster singles/doubles/triples calculations extrapolated to the complete basis set limit and adiabatically corrected for zero point energy. The calculations predict a nonplanar equilibrium structure (θ ≈ 29°, where θ is defined to be 180° minus the angle between the C–F bond and the CH2 plane) with a 132 cm−1 barrier to planarity and a vibrational bend frequency (νbend ≈ 276 cm−1), in good agreement with previous microwave estimates (νbend = 300 (30) cm−1) by Hirota and co-workers [ Y. Endo et al., J. Chem. Phys. 79, 1605 (1983) ]. The nearly 2:1 ratio of absorption intensities for the symmetric versus antisymmetric bands is in good agreement with density functional theory calculations, but in sixfold contrast with simple local mode CH2 bond dipole predictions of 1:3. This discrepancy arises from a surprisingly strong dependence of the symmetric stretch intensity on the inversion bend angle and provides further experimental support for a nonplanar equilibrium structure.
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33.20.Ea Infrared spectra
33.15.Pw Fine and hyperfine structure
33.15.Bh General molecular conformation and symmetry; stereochemistry
31.15.E- Density-functional theory

Density functional study of ion hydration for the alkali metal ions (Li+,Na+,K+) and the halide ions (F−,Br−,Cl−)

Christian Krekeler, Berk Hess, and Luigi Delle Site

J. Chem. Phys. 125, 054305 (2006); http://dx.doi.org/10.1063/1.2218338 (7 pages) | Cited 18 times

Online Publication Date: 2 August 2006

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We performed first principles density functional calculations to study the effect of monovalent ions M+ (M = Li,Na,K) and A− (A = F,Cl,Br) in water with the aim of characterizing the local molecular properties of hydration. For this reason, several ion-water clusters, up to five or six water molecules were considered; such structures were optimized, and the Wannier analysis was then applied to determine the average molecular dipole moment of water. We found that with an increasing number of water molecules, the molecular polarization is determined by the water-water interaction rather than the water-ion interaction, as one would intuitively expect. These results are consistent with those obtained in previous density functional calculations and with other results obtained by employing classical polarizable water models. The main message of this work is that as one increases the number of molecules the average dipole moment of all water molecules and the ones in the first shell tends to the same value as the average of a similar sized cluster of pure water. This supports the use of nonpolarizable classical models of water in classical atomistic simulations.
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61.20.Gy Theory and models of liquid structure
61.25.Em Molecular liquids

Site-selected Auger electron spectroscopy of N2O

Paola Bolognesi, Marcello Coreno, Lorenzo Avaldi, Loriano Storchi, and Francesco Tarantelli

J. Chem. Phys. 125, 054306 (2006); http://dx.doi.org/10.1063/1.2213254 (6 pages) | Cited 8 times

Online Publication Date: 2 August 2006

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The N 1s Auger spectra for the two nonequivalent N atoms in N2O have been measured via Auger electron-photoelectron coincidence spectroscopy. The site-selected Auger spectra are compared with the normal Auger spectrum and with accurate theoretical calculations accounting for the effects of the dynamics of the nuclei on the energy and linewidth of the Auger bands. Such effects are found to be crucial factors in determining the different band shapes in the site-selected spectra.
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33.80.Eh Autoionization, photoionization, and photodetachment
33.60.+q Photoelectron spectra
33.70.Jg Line and band widths, shapes, and shifts

Rotational spectra of 1-chloro-2-fluoroethylene. II. Equilibrium structures of the cis and trans isomer

Cristina Puzzarini, Gabriele Cazzoli, Alberto Gambi, and Jürgen Gauss

J. Chem. Phys. 125, 054307 (2006); http://dx.doi.org/10.1063/1.2220041 (8 pages) | Cited 11 times

Online Publication Date: 3 August 2006

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Equilibrium structures for the cis and trans isomer of 1-chloro-2-fluoroethylene are reported. The structures are obtained within a least-squares fit procedure using the available experimental ground-state rotational constants for various isotopic species of both forms. Vibrational effects were eliminated before the analysis using vibration-rotation interaction constants derived from computed quadratic and cubic force fields with the required quantum chemical calculations carried out using second-order Møller-Plesset perturbation as well as coupled-cluster (CC) theory. The semiexperimental or empirical equilibrium geometries obtained in this way agree well with the corresponding theoretical predictions obtained from CC calculations [at the CCSD(T) level] after extrapolation to the complete basis-set limit and inclusion of core-valence correlation corrections. The present results allow a detailed analysis of the geometrical differences between the two forms of 1-chloro-2-fluoroethylene. They are also compared to the structural data available for other halogenated ethylenes.
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33.20.Sn Rotational analysis
31.15.bw Coupled-cluster theory
33.15.Bh General molecular conformation and symmetry; stereochemistry
33.15.Mt Rotation, vibration, and vibration-rotation constants

Vibrational analyses for CHFClBr and CDFClBr based on high level ab initio calculations

Guntram Rauhut, Vincenzo Barone, and Peter Schwerdtfeger

J. Chem. Phys. 125, 054308 (2006); http://dx.doi.org/10.1063/1.2236112 (7 pages) | Cited 18 times

Online Publication Date: 3 August 2006

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Anharmonicity corrections to the harmonic vibrational spectra of CHFClBr and its deuterated isotopomer were computed by means of variational and perturbational approaches. A comparison of both methods is provided. Based on CCSD(T)/aug-cc-pVTZ electronic structure calculations excellent agreement with experimental data was obtained. Absolute mean deviations are in the range of about 4 cm−1 for the fundamental modes, while slightly larger values of about 7 cm−1 were found for the first vibrational overtones. In addition, vibrationally averaged structural parameters are provided for both molecules. The calculations will serve as a future starting point for parity-violation effects in vibrational transitions in these chiral molecules.
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33.20.Tp Vibrational analysis
33.15.Mt Rotation, vibration, and vibration-rotation constants
31.15.A- Ab initio calculations

The microwave spectrum of the 1,1-difluoroprop-2-ynyl radical, F2math–CCH

Lu Kang and Stewart E. Novick

J. Chem. Phys. 125, 054309 (2006); http://dx.doi.org/10.1063/1.2215599 (8 pages) | Cited 1 time

Online Publication Date: 3 August 2006

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The rotational spectrum of the 1,1-difluoroprop-2-ynyl radical, F2math–CCH, a partially fluorinated variant of the propargyl radical, has been recorded in the ground electronic, math, state using pulsed discharge, pulsed-jet, Fabry-Pérot Fourier transform microwave spectroscopy. Five successive a-type rotational transitions, from N = 1-0 to N = 5-4, and Ka = 0, 1, and 2, were measured between 6.5 and 32.5 GHz with an uncertainty of 5 kHz. The molecular constants, including fine and hyperfine constants, were precisely determined. These constants are compared with our predictions based on a density functional theory level ab initio calculations and with the fine and hyperfine constants of the propargyl radical. The measured electron spin densities suggest that both the difluoropropargyl and the difluoroallenyl resonance forms [F2math–CCH↔F2CCmathH] make major contributions to the electronic structure of the radical.
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33.20.Bx Radio-frequency and microwave spectra
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.15.Pw Fine and hyperfine structure

Dissociation of the OCS+ ion in low-lying electronic states studied using multiconfiguration second-order perturbation theory

Bo-Zhen Chen, Hai-Bo Chang, and Ming-Bao Huang

J. Chem. Phys. 125, 054310 (2006); http://dx.doi.org/10.1063/1.2222357 (9 pages) | Cited 2 times

Online Publication Date: 4 August 2006

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Complete active space self-consistent-field (CASSCF) and multiconfiguration second-order perturbation theory (CASPT2) calculations with atomic natural orbital basis sets were performed to investigate the S-loss direct dissociation of the 1 math(X math), 2 math(A math), 1 math(B math), 1 math, 1 math, and 1 math states of the OCS+ ion and the predissociations of the 1 math, 2 math, and 1 math states. Our calculations indicate that the S-loss dissociation products of the OCS+ ion in the six states are the ground-state CO molecule plus the S+ ion in different electronic states. The CASPT2//CASSCF potential energy curves were calculated for the S-loss dissociation from the six states. The calculations indicate that the dissociation of the 1 math state leads to the CO+S+ (math) products representing the first dissociation limit; the dissociations of the 1 math, 1 math, and 1 math states lead to the CO+S+(math) products representing the second dissociation limit; and the dissociations of the 2 math and 1 math states lead to the CO+S+(math) products representing the third dissociation limit. Seams of the 1 math−1 math, 2 math−1 math, 2 math−1 math, 2 math−1 math, and 1 math−1 math potential energy surface intersections were calculated at the CASPT2 level, and the minima along the seams were located. The calculations indicate that within the experimental energy range (15.07–16.0 eV) the 2 math(A math) state can be predissociated by 1 math forming the S+(math) ion and can undergo internal conversion to 1 math followed by the direct dissociation of 1 math forming S+(math) and that within the experimental energy range (16.04–16.54 eV) the 1 math(B math) state can be predissociated by 1 math forming the S+(math) ion and can undergo internal conversion to 2 math followed by the predissociation of 2 math by 1 math and 1 math forming the S+(math) ion. These indications are in line with the experimental fact that both the math and math states of the S+ ion can be formed from the 2 math and 1 math states of the OCS+ ion.
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33.80.Gj Diffuse spectra; predissociation, photodissociation
82.50.-m Photochemistry
31.15.xr Self-consistent-field methods
31.15.xp Perturbation theory
33.50.Hv Radiationless transitions, quenching

Inversion vibration of PH3+(math math) studied by zero kinetic energy photoelectron spectroscopy

Jie Yang, Juan Li, Yusong Hao, Chang Zhou, and Yuxiang Mo

J. Chem. Phys. 125, 054311 (2006); http://dx.doi.org/10.1063/1.2229211 (12 pages) | Cited 1 time

Online Publication Date: 4 August 2006

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We report the first rotationally resolved spectroscopic studies on PH3+(math math) using zero kinetic energy photoelectron spectroscopy and coherent VUV radiation. The spectra about 8000 cm−1 above the ground vibrational state of PH3+(math math) have been recorded. We observed the vibrational energy level splittings of PH3+(math math) due to the tunneling effect in the inversion (symmetric bending) vibration (ν2+). The energy splitting for the first inversion vibrational state (0+/0−) is 5.8 cm−1. The inversion vibrational energy levels, rotational constants, and adiabatic ionization energies (IEs) for ν2+ = 0–16 have been determined. The bond angles between the neighboring P–H bonds and the P–H bond lengths are also obtained using the experimentally determined rotational constants. With the increasing of the inversion vibrational excitations (ν2+), the bond lengths (P–H) increase a little and the bond angles (H–P–H) decrease a lot. The inversion vibrational energy levels have also been calculated by using one dimensional potential model and the results are in good agreement with the experimental data for the first several vibrational levels. In addition to inversion vibration, we also observed firstly the other two vibrational modes: the symmetric P–H stretching vibration (ν1+) and the degenerate bending vibration (ν4+). The fundamental frequencies for ν1+ and ν4+ are 2461.6 (±2) and 1043.9 (±2) cm−1, respectively. The first IE for PH3 was determined as 79670.9 (±1) cm−1.
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33.60.+q Photoelectron spectra
33.20.Tp Vibrational analysis
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.15.Ry Ionization potentials, electron affinities, molecular core binding energy
33.15.Dj Interatomic distances and angles

Accurate computational determination of the binding energy of the SO3∙H2O complex

Heike Fliegl, Andreas Glöß, Oliver Welz, Matthias Olzmann, and Wim Klopper

J. Chem. Phys. 125, 054312 (2006); http://dx.doi.org/10.1063/1.2234372 (7 pages) | Cited 9 times

Online Publication Date: 7 August 2006

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Reliable thermochemical data for the reaction SO3+H2O⇔SO3∙H2O ( 1a ) are of crucial importance for an adequate modeling of the homogeneous H2SO4 formation in the atmosphere. We report on high-level quantum chemical calculations to predict the binding energy of the SO3∙H2O complex. The electronic binding energy is accurately computed to De = 40.9±1.0 kJ/mol = 9.8±0.2 kcal/mol. By using harmonic frequencies from density functional theory calculations (B3LYP/cc-pVTZ and TPSS/def2-TZVP), zero-point and thermal energies were calculated. From these data, we estimate D0 = −ΔH1a0(0 K) = 7.7±0.5 kcal/mol and ΔH1a0(298 K) = −8.3±1.0 kcal/mol.
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82.33.Tb Atmospheric chemistry
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
33.15.Ry Ionization potentials, electron affinities, molecular core binding energy

Rotational spectra of 1-chloro-2-fluoroethylene. I. Main isotopologues and deuterated species of the trans isomer

Gabriele Cazzoli, Cristina Puzzarini, Alberto Gambi, and Jürgen Gauss

J. Chem. Phys. 125, 054313 (2006); http://dx.doi.org/10.1063/1.2217372 (8 pages) | Cited 6 times

Online Publication Date: 7 August 2006

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Guided by theoretical predictions, the rotational spectra of the mono- and bideuterated species of trans-1-chloro-2-fluoroethylene, CHmathCDF, CHmathCDF, CDmathCHF, CDmathCHF, CDmathCDF, and CDmathCDF, have been recorded for the first time. Assignment of the ΔJ = 0 and ΔK−1 = +1 bands with K−1 = 3,4,5,… (all isotopic species) as well as of several ΔJ = ±1 and ΔK−1 = +1 transitions (all isotopic species except CHmathCDF, CDmathCHF, and CDmathCDF) led to the accurate determination of the ground-state rotational constants, the quartic, and some sextic centrifugal distortion constants, as well as the nuclear quadrupole coupling constants for both math and math in good agreement with corresponding theoretical predictions based on high-level coupled-cluster calculations. Inconsistencies of the present spectroscopic parameters with respect to those reported earlier for the two main isotopologues, i.e., CHmathCHF and CHmathCHF, necessitated a reinvestigation of the rotational spectra for these two isotopic species. Supported by quantum chemical calculations, the previously recorded spectra are reassigned to a vibrationally excited state, while analysis of the ΔJ = 0 and ΔK−1 = +1 as well as some ΔJ = ±1 and ΔK−1 = +1 transitions provided a revised set of spectroscopic parameters for the vibrational ground state of these two isotopic species.
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33.20.Sn Rotational analysis
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.15.Bh General molecular conformation and symmetry; stereochemistry
31.30.Gs Hyperfine interactions and isotope effects
31.15.-p Calculations and mathematical techniques in atomic and molecular physics
33.20.Tp Vibrational analysis
back to top Condensed Phase Dynamics, Structure, and Thermodynamics: Spectroscopy, Reactions, and Relaxation

Light-harvesting function through one-by-one electron and hole transfer in a methane-lithium system

Yasunobu Kodama and Kaoru Ohno

J. Chem. Phys. 125, 054501 (2006); http://dx.doi.org/10.1063/1.2227024 (6 pages) | Cited 7 times

Online Publication Date: 1 August 2006

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Carrying out a semiclassical molecular dynamics simulation of a CH4–Li2 system by using the time-dependent local density approximation of the time-dependent density functional theory, we find that one-by-one electron and hole transfer takes place from CH4 to Li2 when an electron is excited in CH4. Probability of the transfer is low when the molecules are fixed, but it increases when the molecules are freely relaxed or Li2 has 1 eV of initial velocity.
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82.50.-m Photochemistry
82.20.Ln Semiclassical theory of reactions and/or energy transfer
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