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7 Feb 2010

Volume 132, Issue 5, Articles (05xxxx)

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J. Chem. Phys. 132, 054101 (2010); http://dx.doi.org/10.1063/1.3273617 (9 pages)

Marianne S. Bauer, Birgit Strodel, Szilard N. Fejer, Elena F. Koslover, and David J. Wales
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Communications: Infrared spectroscopy of gas phase C3H3+ ions: The cyclopropenyl and propargyl cations

Allen M. Ricks, Gary E. Douberly, Paul v. R. Schleyer, and Michael A. Duncan

J. Chem. Phys. 132, 051101 (2010); http://dx.doi.org/10.1063/1.3298881 (4 pages) | Cited 12 times

Online Publication Date: 2 February 2010

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C3H3+ ions produced with a pulsed discharge source and cooled in a supersonic beam are studied with infrared laser photodissociation spectroscopy in the 800–4000 cm−1 region using the rare gas tagging method. Vibrational bands in the C–H stretching and fingerprint regions confirm the presence of both the cyclopropenyl and propargyl cations. Because there is a high barrier separating these two structures, they are presumed to be produced by different routes in the plasma chemistry; their relative abundance can be adjusted by varying the ion source conditions. Prominent features for the cyclopropenyl species include the asymmetric carbon stretch (ν5) at 1293 cm−1 and the asymmetric C–H stretch (ν4) at 3182 cm−1, whereas propargyl has the CH2 scissors (ν4) at 1445, the C–C triple bond stretch (ν3) at 2077 and three C–H stretches (ν2, ν9, and ν1) at 3004, 3093, and 3238 cm−1. Density functional theory computations of vibrational spectra for the two isomeric ions with and without the argon tag reproduce the experimental features qualitatively; according to theory the tag atom only perturbs the spectra slightly. Although these data confirm the accepted structural pictures of the cyclopropenyl and propargyl cations, close agreement between theoretical predictions and the measured vibrational band positions and intensities cannot be obtained. Band intensities are influenced by the energy dependence and dynamics of photodissociation, but there appear to be fundamental problems in computed band positions independent of the level of theory employed. These new data provide infrared signatures in the fingerprint region for these prototypical carbocations that may aid in their astrophysical detection.
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33.80.Gj Diffuse spectra; predissociation, photodissociation
33.20.Tp Vibrational analysis
33.20.Ea Infrared spectra
31.15.es Applications of density-functional theory (e.g., to electronic structure and stability; defect formation; dielectric properties, susceptibilities; viscoelastic coefficients; Rydberg transition frequencies)
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Interpolation schemes for peptide rearrangements

Marianne S. Bauer, Birgit Strodel, Szilard N. Fejer, Elena F. Koslover, and David J. Wales

J. Chem. Phys. 132, 054101 (2010); http://dx.doi.org/10.1063/1.3273617 (9 pages) | Cited 2 times

Online Publication Date: 1 February 2010

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A variety of methods (in total seven) comprising different combinations of internal and Cartesian coordinates are tested for interpolation and alignment in connection attempts for polypeptide rearrangements. We consider Cartesian coordinates, the internal coordinates used in CHARMM, and natural internal coordinates, each of which has been interfaced to the OPTIM code and compared with the corresponding results for united-atom force fields. We show that aligning the methylene hydrogens to preserve the sign of a local dihedral angle, rather than minimizing a distance metric, provides significant improvements with respect to connection times and failures. We also demonstrate the superiority of natural coordinate methods in conjunction with internal alignment. Checking the potential energy of the interpolated structures can act as a criterion for the choice of the interpolation coordinate system, which reduces failures and connection times significantly.
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87.15.B- Structure of biomolecules
02.60.Ed Interpolation; curve fitting

Relativistic quantum Monte Carlo method using zeroth-order regular approximation Hamiltonian

Yutaka Nakatsuka, Takahito Nakajima, Maho Nakata, and Kimihiko Hirao

J. Chem. Phys. 132, 054102 (2010); http://dx.doi.org/10.1063/1.3298912 (7 pages) | Cited 6 times

Online Publication Date: 1 February 2010

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We propose a new relativistic treatment in the quantum Monte Carlo (QMC) technique using the zeroth-order regular approximation (ZORA) Hamiltonian. The novel ZORA local energy is derived, and its availability is examined with some variational Monte Carlo calculations. We optimize the wave functions variationally and evaluate the relativistic and correlation effects simultaneously. It is shown that our ZORA-QMC method with Jastrow–Slater wave functions can recover not only relativistic effects but also almost the same amount of electron correlations as the nonrelativistic QMC method can by evaluating the ionization potentials of the first row atoms, Li–Ne.
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31.15.V- Electron correlation calculations for atoms, ions and molecules
32.50.+d Fluorescence, phosphorescence (including quenching)

Variational geminal-augmented multireference self-consistent field theory: Two-electron systems

Sergey A. Varganov and Todd J. Martínez

J. Chem. Phys. 132, 054103 (2010); http://dx.doi.org/10.1063/1.3303203 (8 pages) | Cited 8 times

Online Publication Date: 1 February 2010

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We introduce a geminal-augmented multiconfigurational self-consistent field method for describing electron correlation effects. The approach is based on variational optimization of a MCSCF-type wave function augmented by a single geminal. This wave function is able to account for some dynamic correlation without explicit excitations to virtual molecular orbitals. Test calculations on two-electron systems demonstrate the ability of the proposed method to describe ionic and covalent electronic states in a balanced way, i.e., including the effects of both static and dynamic correlation simultaneously. Extension of the theory to larger systems will potentially provide an alternative to standard multireference methods.
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31.15.xr Self-consistent-field methods
31.15.ve Electron correlation calculations for atoms and ions: ground state
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Short-time Fourier transform analysis of real-time time-dependent Hartree–Fock and time-dependent density functional theory calculations with Gaussian basis functions

Tomoko Akama and Hiromi Nakai

J. Chem. Phys. 132, 054104 (2010); http://dx.doi.org/10.1063/1.3300127 (11 pages) | Cited 5 times

Online Publication Date: 2 February 2010

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We propose a novel analysis of real-time (RT) time-dependent Hartree–Fock and time-dependent density functional theory (TDHF/TDDFT) calculations using a short-time Fourier transform (STFT) technique. RT-TDHF/TDDFT calculations of model dimers were carried out and analyzed using the STFT technique, in addition to the usual Fourier transform (FT). STFT analysis revealed that the induced polarization propagated between the molecules through the intermolecular interaction; that is, it directly showed the electron dynamics of the excited system. The dependence of the propagation period on the intermolecular distance of the dimer was investigated. We also proved the possibility of describing, not just the valence, but also the core excitations by FT analysis of the RT-TDHF/TDDFT calculations of a formaldehyde monomer with Gaussian basis functions compared with conventional TDHF/TDDFT results.
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31.15.ee Time-dependent density functional theory
31.15.xr Self-consistent-field methods
34.20.Gj Intermolecular and atom-molecule potentials and forces

Method and basis set dependence of anharmonic ground state nuclear wave functions and zero-point energies: Application to SSSH

Stephen J. Kolmann and Meredith J. T. Jordan

J. Chem. Phys. 132, 054105 (2010); http://dx.doi.org/10.1063/1.3276064 (10 pages) | Cited 1 time

Online Publication Date: 2 February 2010

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One of the largest remaining errors in thermochemical calculations is the determination of the zero-point energy (ZPE). The fully coupled, anharmonic ZPE and ground state nuclear wave function of the SSSH radical are calculated using quantum diffusion Monte Carlo on interpolated potential energy surfaces (PESs) constructed using a variety of method and basis set combinations. The ZPE of SSSH, which is approximately 29 kJ mol−1 at the CCSD(T)/6-31G∗ level of theory, has a 4 kJ mol−1 dependence on the treatment of electron correlation. The anharmonic ZPEs are consistently 0.3 kJ mol−1 lower in energy than the harmonic ZPEs calculated at the Hartree–Fock and MP2 levels of theory, and 0.7 kJ mol−1 lower in energy at the CCSD(T)/6-31G∗ level of theory. Ideally, for sub-kJ mol−1 thermochemical accuracy, ZPEs should be calculated using correlated methods with as big a basis set as practicable. The ground state nuclear wave function of SSSH also has significant method and basis set dependence. The analysis of the nuclear wave function indicates that SSSH is localized to a single symmetry equivalent global minimum, despite having sufficient ZPE to be delocalized over both minima. As part of this work, modifications to the interpolated PES construction scheme of Collins and co-workers are presented.
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82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
82.60.-s Chemical thermodynamics
82.20.Kh Potential energy surfaces for chemical reactions
82.20.Wt Computational modeling; simulation

Circumstantial evidence in support of bivelocity hydrodynamic theory for mixtures

Howard Brenner

J. Chem. Phys. 132, 054106 (2010); http://dx.doi.org/10.1063/1.3298996 (6 pages) | Cited 4 times

Online Publication Date: 2 February 2010

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Based upon findings with respect to the viability of the expression jv = −ρDv∇math hypothesized to represent the constitutive equation for the diffusive volume flux in ideal binary mixtures (ρ = mass density, math = 1/ρ = specific volume, and Dv = volume diffusion coefficient), implicit evidence is offered in support of the recently developed theory of bivelocity continuum hydrodynamics for mixtures. Present findings for the case of mixtures add to existing evidence already available for the single-component case, thus supporting the viability of bivelocity hydrodynamic theory in general.
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47.10.A- Mathematical formulations
05.60.-k Transport processes
05.70.Ln Nonequilibrium and irreversible thermodynamics

The “weighted ensemble” path sampling method is statistically exact for a broad class of stochastic processes and binning procedures

Bin W. Zhang, David Jasnow, and Daniel M. Zuckerman

J. Chem. Phys. 132, 054107 (2010); http://dx.doi.org/10.1063/1.3306345 (7 pages) | Cited 7 times

Online Publication Date: 2 February 2010

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The “weighted ensemble” method, introduced by Huber and Kim [Biophys. J. 70, 97 (1996) ], is one of a handful of rigorous approaches to path sampling of rare events. Expanding earlier discussions, we show that the technique is statistically exact for a wide class of Markovian and non-Markovian dynamics. The derivation is based on standard path-integral (path probability) ideas, but recasts the weighted-ensemble approach as simple “resampling” in path space. Similar reasoning indicates that arbitrary nonstatic binning procedures, which merely guide the resampling process, are also valid. Numerical examples confirm the claims, including the use of bins which can adaptively find the target state in a simple model.
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02.50.Ey Stochastic processes
02.50.Cw Probability theory
02.50.Ga Markov processes
02.60.-x Numerical approximation and analysis

Correlation consistent basis sets for molecular core-valence effects with explicitly correlated wave functions: The atoms B–Ne and Al–Ar

J. Grant Hill, Shivnath Mazumder, and Kirk A. Peterson

J. Chem. Phys. 132, 054108 (2010); http://dx.doi.org/10.1063/1.3308483 (12 pages) | Cited 23 times

Online Publication Date: 4 February 2010

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Correlation consistent basis sets have been optimized for accurately describing core-core and core-valence correlation effects with explicitly correlated F12 methods. The new sets, denoted cc-pCVnZ-F12 (n = D, T, Q) and aug-cc-pCF12VnZ (n = D, T, Q, 5), were developed by augmenting the cc-pVnZ-F12 and aug-cc-pVnZ families of basis sets with additional functions whose exponents were optimized based on the difference between all-electron and valence-electron correlation energies. The number of augmented functions added is fewer, in general, than in the standard cc-pCVnZ and cc-pwCVnZ families of basis sets. Optimal values of the geminal Slater exponent for use with these basis sets in MP2-F12 calculations are presented and are also recommended for CCSD-F12b calculations. Auxiliary basis sets for use in the resolution of the identity approximation in explicitly correlated calculations have also been optimized and matched to the new cc-pCVnZ-F12 series of orbital basis sets. The cc-pCVnZ-F12 basis sets, along with the new auxiliary sets, were benchmarked in CCSD(T)-F12b calculations of spectroscopic properties on a series of homo- and heteronuclear first and second row diatomic molecules. Comparing the effects of correlating the outer core electrons in these molecules with those from conventional CCSD(T) at the complete basis set limit, which involved calculations with new cc-pCV6Z basis sets for the second row elements that were also developed in the course of this work, it is observed that the F12 values are reasonably well converged already at just the triple-ζ level.
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31.15.vn Electron correlation calculations for diatomic molecules
31.15.bw Coupled-cluster theory

Accelerating self-consistent field convergence with the augmented Roothaan–Hall energy function

Xiangqian Hu and Weitao Yang

J. Chem. Phys. 132, 054109 (2010); http://dx.doi.org/10.1063/1.3304922 (7 pages) | Cited 4 times

Online Publication Date: 4 February 2010

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Based on Pulay’s direct inversion iterative subspace (DIIS) approach, we present a method to accelerate self-consistent field (SCF) convergence. In this method, the quadratic augmented Roothaan–Hall (ARH) energy function, proposed recently by Høst and co-workers [J. Chem. Phys. 129, 124106 (2008)] , is used as the object of minimization for obtaining the linear coefficients of Fock matrices within DIIS. This differs from the traditional DIIS of Pulay, which uses an object function derived from the commutator of the density and Fock matrices. Our results show that the present algorithm, abbreviated ADIIS, is more robust and efficient than the energy-DIIS (EDIIS) approach. In particular, several examples demonstrate that the combination of ADIIS and DIIS (“ADIIS+DIIS”) is highly reliable and efficient in accelerating SCF convergence.
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31.15.xr Self-consistent-field methods

B3LYP calculations of cerium oxides

Jolla Kullgren, Christopher W. M. Castleton, Carsten Müller, David Muñoz Ramo, and Kersti Hermansson

J. Chem. Phys. 132, 054110 (2010); http://dx.doi.org/10.1063/1.3253795 (12 pages) | Cited 7 times

Online Publication Date: 5 February 2010

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In this paper we evaluate the performance of density functional theory with the B3LYP functional for calculations on ceria (CeO2) and cerium sesquioxide (Ce2O3). We demonstrate that B3LYP is able to describe CeO2 and Ce2O3 reasonably well. When compared to other functionals, B3LYP performs slightly better than the hybrid functional PBE0 for the electronic properties but slightly worse for the structural properties, although neither performs as well as LDA+U(U = 6 eV) or PBE+U(U = 5 eV). We also make an extensive comparison of atomic basis sets suitable for periodic calculations of these cerium oxides. Here we conclude that there is currently only one type of cerium basis set available in the literature that is able to give a reasonable description of the electronic structure of both CeO2 and Ce2O3. These basis sets are based on a 28 electron effective core potential (ECP) and 30 electrons are attributed to the valence space of cerium. Basis sets based on 46 electron ECPs fail for these materials.
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71.15.Mb Density functional theory, local density approximation, gradient and other corrections
61.66.Fn Inorganic compounds
71.20.Ps Other inorganic compounds
62.20.dq Other elastic constants
81.40.Jj Elasticity and anelasticity, stress-strain relations

Critical behavior of interacting monomers adsorbed on one-dimensional channels arranged in a triangular cross-sectional structure: Mixed interactions along and across the channels

P. M. Pasinetti, F. Romá, J. L. Riccardo, and A. J. Ramirez-Pastor

J. Chem. Phys. 132, 054111 (2010); http://dx.doi.org/10.1063/1.3292680 (7 pages) | Cited 2 times

Online Publication Date: 5 February 2010

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Monte Carlo simulations and finite-size scaling analysis have been carried out to study the critical behavior in a submonolayer lattice-gas which mimics a nanoporous environment. In this model, the adsorbent is modeled as one-dimensional channels of equivalent adsorption sites arranged in a triangular cross-sectional structure. Two kinds of lateral interaction energies have been considered: (1) wL interaction energy between nearest-neighbor particles adsorbed along a single channel and (2) wT interaction energy between particles adsorbed across nearest-neighbor channels. We focus on the case of repulsive transverse (wT>0) and attractive longitudinal (wL<0) lateral interactions, where a rich variety of structural orderings are observed in the adlayer depending on the value of the parameters kBT/wT (being kB the Boltzmann constant) and wL/wT. The results reveal the existence of a first-order phase transition in the adlayer between a low-temperature “condensed” phase and a high-temperature “disordered” phase.
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68.43.Mn Adsorption kinetics
68.35.Rh Phase transitions and critical phenomena
61.43.Gt Powders, porous materials
61.46.-w Structure of nanoscale materials
64.60.fd General theory of critical region behavior
back to top Gas Phase Dynamics and Structure: Spectroscopy, Molecular Interactions, Scattering, and Photochemistry

Hyperfine interaction and Stark effect in the b math-X math+(0,0) band of copper monofluoride, CuF

Fang Wang and Timothy C. Steimle

J. Chem. Phys. 132, 054301 (2010); http://dx.doi.org/10.1063/1.3292606 (8 pages) | Cited 5 times

Online Publication Date: 2 February 2010

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The low-rotational levels of the b math-X math+(0,0) band of copper monofluoride, CuF, were recorded field free and in the presence of a static electric field. The field-free spectrum was analyzed to produce a refined set of fine and hyperfine parameters for the b math(v = 0) state. The permanent electric dipole moment, μ, for the b math(v = 0) and X math+(v = 0) states were determined to be 2.36(2) and 5.26(2) D, respectively, from the analysis of the observed Stark shifts. The experimental μ values are compared to theoretical predictions. The change in μ upon excitation and the hyperfine parameters are discussed in terms of the proposed electronic configuration for the b math and X math+ states. The optical Stark spectroscopy of the A math3/2-X math+(0,0) subband of YO was also recorded and analyzed to precisely calibrate the electric field strength. The determined μ values are 3.714(5) and 4.542(40) D for the A math3/2(v = 0) and X math+(v = 0) states, respectively.
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33.57.+c Magneto-optical and electro-optical spectra and effects
33.20.Sn Rotational analysis
33.15.Mt Rotation, vibration, and vibration-rotation constants

Theoretical study of the bonding in Mn+-RG complexes and the transport of Mn+ through rare gas (M = Ca, Sr, and Ra; n = 1 and 2; and RG = He–Rn)

Adrian M. Gardner, Carolyn D. Withers, Timothy G. Wright, Kimberly I. Kaplan, Chivone Y. N. Chapman, Larry A. Viehland, Edmond P. F. Lee, and W. H. Breckenridge

J. Chem. Phys. 132, 054302 (2010); http://dx.doi.org/10.1063/1.3297891 (11 pages) | Cited 11 times

Online Publication Date: 3 February 2010

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We present high level ab initio potential energy curves for the Mn+-RG complexes, where n = 1 and 2; RG = He–Rn; and M = Ca, Sr, and Ra. Spectroscopic constants have been derived from these potentials and are compared with a wide range of experimental and previous theoretical data, and good agreement is generally seen. Large changes in binding energy, De, and bond length, Re, between M+–He, M+–Ne, and M+–Ar, also found previously in the analogous Ba+-RG complexes [ M. F. McGuirk et al., J. Chem. Phys. 130, 194305 (2009) ], are identified and the cause investigated; the results shed light on the previous Ba+-RG results. These unusual trends are not observed for the dicationic complexes, which behave in a fashion similar to the isoelectronic alkali metal ion complexes. The potentials have also been employed to calculate transport coefficients for Mn+ moving through a bath of rare gas (RG) atoms.
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34.20.Gj Intermolecular and atom-molecule potentials and forces
31.15.at Molecule transport characteristics; molecular dynamics; electronic structure of polymers
33.15.Ry Ionization potentials, electron affinities, molecular core binding energy
33.15.Dj Interatomic distances and angles

Excited states of PbF: A four-component relativistic study

Shigeyoshi Yamamoto and Hiroshi Tatewaki

J. Chem. Phys. 132, 054303 (2010); http://dx.doi.org/10.1063/1.3298583 (10 pages) | Cited 3 times

Online Publication Date: 3 February 2010

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The electronic states of lead monofluoride (PbF) are studied from the (Pb 6s)2 (F 2p-π)4 (F 2p-σ)2 (Pb 6p-π)1 X1 ground state up to the F state, using the four-component relativistic configuration interaction and Fock-space coupled-cluster singles and doubles methods. Difficulties arising from the valence-Rydberg mixing are overcome by using a flexible basis set including Rydberg-type diffuse functions and by large-scale correlation calculations. The excited states are successfully characterized with the help of computed transition dipole moments. The three lowest-lying states (X1, X2, and A) are confirmed to be valence states arising from the (Pb 6p) spinors. The B state is assigned to the lowest Rydberg state (Ω = 1/2), represented by a single excitation from the (Pb 6p-π) spinor to the (F 3s) Rydberg spinor. Its calculated excitation energy (4.30 eV) is comparable to the observed one (4.42 eV). The C state is a multiconfigurational valence state whose dominant configuration is represented by (Pb 6s)2 (F 2p-π)4 (F 2p-σ)1 (Pb 6p-π)2. Its calculated excitation energy (4.71 eV) is in good agreement with experiment (4.72 eV). The remaining D, E, and F states are assigned as Rydberg states. The calculated ionization potential (7.44 eV) is also close to the value (7.55 eV) determined recently by multiphoton ionization experiments.
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31.15.vn Electron correlation calculations for diatomic molecules
31.15.ve Electron correlation calculations for atoms and ions: ground state
31.15.vj Electron correlation calculations for atoms and ions: excited states
31.15.bw Coupled-cluster theory
33.70.Ca Oscillator and band strengths, lifetimes, transition moments, and Franck-Condon factors
33.15.Ry Ionization potentials, electron affinities, molecular core binding energy

Reinvestigation of the Rb2 (2)mathg−a mathu+ band on helium nanodroplets

G. Auböck, M. Aymar, O. Dulieu, and W. E. Ernst

J. Chem. Phys. 132, 054304 (2010); http://dx.doi.org/10.1063/1.3308493 (7 pages) | Cited 8 times

Online Publication Date: 4 February 2010

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It is well known that alkali-metal molecules are preferentially observed in the weak van der Waals-bound high spin states by helium droplet isolation spectroscopy. In [ F. R. Brühl et al., J. Chem. Phys. 115, 10275 (2001) ] the Rb2 (2)mathg−a mathu+ band on He droplets was investigated by laser-induced fluorescence and dispersed emission spectroscopy. At that time no information on the magnitude of spin-orbit coupling was available for the (2)mathg state which connects to the atomic 5s+4d asymptote and it was neglected. In this work we reinvestigate the observed spectra. The dispersed emission spectra, which resulted from free molecules, are consistent with state-of-the-art nonrelativistic potential energy surfaces and effective spin-orbit coupling matrix elements obtained from resonance-enhanced multiphoton ionization spectroscopy of cold Rb dimers [ J. Lozeille et al., Eur. Phys. J. D 39, 261 (2006) ]. Having validated the theoretical description of the free molecule state, we use the laser-induced fluorescence spectrum to discuss the influence of the He droplet on the excitation band.
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33.80.Eh Autoionization, photoionization, and photodetachment
33.80.Rv Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states)
33.50.Dq Fluorescence and phosphorescence spectra
31.50.Df Potential energy surfaces for excited electronic states
34.20.Cf Interatomic potentials and forces
FREE

Isomer identification and resolution in small gold clusters

Wei Huang, Rhitankar Pal, Lei-Ming Wang, Xiao Cheng Zeng, and Lai-Sheng Wang

J. Chem. Phys. 132, 054305 (2010); http://dx.doi.org/10.1063/1.3299292 (5 pages) | Cited 12 times

Online Publication Date: 5 February 2010

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A variety of experimental techniques are used to resolve energetically close isomers of Au7− and Au8− by combining photoelectron spectroscopy and ab initio calculations. Two structurally distinct isomers are confirmed to exist in the cluster beam for both clusters. Populations of the different isomers in the cluster beam are tuned using Ar-tagging, O2-titration, and isoelectronic atom substitution by Cu and Ag. A new isomer structure is found for Au7−, which consists of a triangular Au6 unit with a dangling Au atom. Isomer-specific photoelectron spectra of Au8− are obtained from O2-titration experiment. The global minimum and low-lying structures of Au7−, Au8−, and MAun− (n = 6,7; M = Ag,Cu) are obtained through basin-hopping global minimum searches. The results demonstrate that the combination of well-designed photoelectron spectroscopy experiments (including Ar-tagging, O2-titration, and isoelectronic substitution) and ab initio calculation is not only powerful for obtaining the electronic and atomic structures of size-selected clusters, but also valuable in resolving structurally and energetically close isomers of nanoclusters.
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36.40.Wa Charged clusters
36.40.Mr Spectroscopy and geometrical structure of clusters
31.15.bw Coupled-cluster theory
33.15.Hp Barrier heights (internal rotation, inversion, rotational isomerism, conformational dynamics)

Indistinguishability and interference in the coherent control of atomic and molecular processes

Jiangbin Gong and Paul Brumer

J. Chem. Phys. 132, 054306 (2010); http://dx.doi.org/10.1063/1.3304921 (11 pages) | Cited 3 times

Online Publication Date: 5 February 2010

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The subtle and fundamental issue of indistinguishability and interference between independent pathways to the same target state is examined in the context of coherent control of atomic and molecular processes, with emphasis placed on possible “which-way” information due to quantum entanglement established in the quantum dynamics. Because quantum interference between independent pathways to the same target state occurs only when the independent pathways are indistinguishable, it is first shown that creating useful coherence between nondegenerate states of a molecule for subsequent quantum interference manipulation cannot be achieved by collisions between atoms or molecules that are prepared in momentum and energy eigenstates. Coherence can, however, be transferred from light fields to atoms or molecules. Using a particular coherent control scenario, it is shown that this coherence transfer and the subsequent coherent phase control can be readily realized by the most classical states of light, i.e., coherent states of light. It is further demonstrated that quantum states of light may suppress the extent of phase-sensitive coherent control by leaking out some which-way information while “incoherent interference control” scenarios proposed in the literature have automatically ensured the indistinguishability of multiple excitation pathways. The possibility of quantum coherence in photodissociation product states is also understood in terms of the disentanglement between photodissociation fragments. Results offer deeper insights into quantum coherence generation in atomic and molecular processes.
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33.80.Gj Diffuse spectra; predissociation, photodissociation
03.67.Mn Entanglement measures, witnesses, and other characterizations
42.50.-p Quantum optics
42.25.Kb Coherence
32.80.-t Photoionization and excitation
03.65.-w Quantum mechanics
back to top Condensed Phase Dynamics, Structure, and Thermodynamics: Spectroscopy, Reactions, and Relaxation

Anomalous nonlinear response of glassy liquids: General arguments and a mode-coupling approach

Marco Tarzia, Giulio Biroli, Alexandre Lefèvre, and Jean-Philippe Bouchaud

J. Chem. Phys. 132, 054501 (2010); http://dx.doi.org/10.1063/1.3290986 (10 pages) | Cited 2 times

Online Publication Date: 1 February 2010

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We study theoretically the nonlinear response properties of glass formers. We establish several general results, which together with the assumption of time-temperature superposition, lead to a relation between the nonlinear response and the derivative of the linear response with respect to temperature. Using results from mode-coupling theory and scaling arguments valid close to the glass transition, we obtain the frequency and temperature dependence of the nonlinear response in the α- and β-regimes. Our results demonstrate that supercooled liquids are characterized by responses to external perturbations that become increasingly nonlinear as the glass transition is approached. These results are extended to the case of inhomogeneous perturbing fields.
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61.20.Lc Time-dependent properties; relaxation
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition

Modeling the solid-liquid phase transition in saturated triglycerides

David A. Pink, Charles B. Hanna, Christophe Sandt, Adam J. MacDonald, Ronald MacEachern, Robert Corkery, and Dérick Rousseau

J. Chem. Phys. 132, 054502 (2010); http://dx.doi.org/10.1063/1.3276108 (11 pages) | Cited 1 time

Online Publication Date: 2 February 2010

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We investigated theoretically two competing published scenarios for the melting transition of the triglyceride trilaurin (TL): those of (1) Corkery et al. [Langmuir 23, 7241 (2007)] , in which the average state of each TL molecule in the liquid phase is a discotic “Y” conformer whose three chains are dynamically twisted, with an average angle of ∼ 120° between them, and those of (2) Cebula et al. [J. Am. Oil Chem. Soc. 69, 130 (1992)] , in which the liquid-state conformation of the TL molecule in the liquid phase is a nematic h∗-conformer whose three chains are in a modified “chair” conformation. We developed two competing models for the two scenarios, in which TL molecules are in a nematic compact-chair (or “h”) conformation, with extended, possibly all-trans, chains at low-temperatures, and in either a Y conformation or an h∗ conformation in the liquid state at temperatures higher than the phase-transition temperature, T∗ = 319 K. We defined an h-Y model as a realization of the proposal of Corkery et al. [Langmuir 23, 7241 (2007)] , and explored its predictions by mapping it onto an Ising model in a temperature-dependent field, performing a mean-field approximation, and calculating the transition enthalpy ΔH. We found that the most plausible realization of the h-Y model, as applied to the solid-liquid phase transition in TL, and likely to all saturated triglycerides, gave a value of ΔH in reasonable agreement with the experiment. We then defined an alternative h-h∗ model as a realization of the proposal of Cebula et al. [J. Am. Oil Chem. Soc. 69, 130 (1992)] , in which the liquid phase exhibits an average symmetry breaking similar to an h conformation, but with twisted chains, to see whether it could describe the TL phase transition. The h-h∗ model gave a value of ΔH that was too small by a factor of ∼ 3–4. We also predicted the temperature dependence of the 1132 cm−1 Raman band for both models, and performed measurements of the ratios of three TL Raman bands in the temperature range of −20 °C ≤ T ≤ 90 °C. The experimental results were in accord with the predictions of the h-Y model and support the proposal of Corkery et al. [Langmuir 23, 7241 (2007)] that the liquid state is made up of molecules that are each, on average, in a Y conformation. Finally, we carried out computer simulations of minimal-model TLs in the liquid phase, and concluded that although the individual TL molecules are, on average, Y conformers, long-range discotic order is unlikely to exist.
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64.70.mf Theory and modeling of specific liquid crystal transitions, including computer simulation
64.70.dj Melting of specific substances
61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
61.30.Cz Molecular and microscopic models and theories of liquid crystal structure
65.20.Jk Studies of thermodynamic properties of specific liquids
82.60.Fa Heat capacities and heats of phase transitions
78.30.cb Organic liquids

The longitudinal optic-like mode in molten alkali halides: A molecular dynamics approximation to inelastic x-ray scattering experiments

O. Alcaraz and J. Trullàs

J. Chem. Phys. 132, 054503 (2010); http://dx.doi.org/10.1063/1.3298863 (10 pages)

Online Publication Date: 2 February 2010

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The contribution of the long-wavelength fluctuations in the particle number, mass, and charge densities to the inelastic x-ray scattering dynamical structure factor for molten NaI and other molten alkali halides is accurately analyzed in the high frequencies region of the longitudinal optic-like mode. Molecular dynamics simulation results at low wave numbers are reported for the time correlations between the density components in the reciprocal space, namely, the corresponding intermediate scattering functions, and their spectra, namely, the dynamical structure factors. The time correlations between the longitudinal currents and their spectra are also reported. The importance of cross correlations is discussed. Moreover, the role played by the collective behavior of the two ionic species is also investigated. It is concluded that the longitudinal optic-like mode in molten alkali halides is unlikely to be detected by inelastic x-ray scattering experiments.
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61.20.Ja Computer simulation of liquid structure
61.20.Lc Time-dependent properties; relaxation
61.20.Qg Structure of associated liquids: electrolytes, molten salts, etc.
64.70.dj Melting of specific substances

Reactions of ruthenium and rhodium atoms with carbon monoxide and dinitrogen mixtures: A combined experimental and theoretical study

Ling Jiang, Zhang-Hui Lu, and Qiang Xu

J. Chem. Phys. 132, 054504 (2010); http://dx.doi.org/10.1063/1.3299715 (8 pages) | Cited 3 times

Online Publication Date: 3 February 2010

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Laser-ablated Ru and Rh atoms react with CO and N2 mixture in excess neon to produce the carbonylmetal dinitrogen complexes, (NN)nMCO (M = Ru,Rh; n = 1,2) and NNRu(CO)2, as well as metal carbonyls and dinitrogen complexes. These carbonylmetal dinitrogen complexes are characterized using infrared spectroscopy on the basis of the results of the isotopic substitution and mixed isotopic splitting patterns. Density functional theory calculations have been performed on these complexes. Overall agreement between the experimental and calculated vibrational frequencies, relative absorption intensities, and isotopic shifts supports the identification of these species from the matrix infrared spectra. Furthermore, a plausible reaction pathway for the formation of the products has been proposed. This work reveals that the reactivity of Ru and Rh atoms toward CO is prior to N2.
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82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
31.15.E- Density-functional theory
33.20.Ea Infrared spectra
33.20.Tp Vibrational analysis

Retardation effects breaking long-range orientational ordering in dipolar fluids

Gunnar Karlström and Per Linse

J. Chem. Phys. 132, 054505 (2010); http://dx.doi.org/10.1063/1.3305325 (5 pages) | Cited 1 time

Online Publication Date: 3 February 2010

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A strongly coupled dipolar fluid confined in a sphere has been examined by Monte Carlo simulations using a modified distance-dependent pair interaction to emulate retardation effects. The effective dipole-dipole interaction and a property closely related to Kirkwood’s g-factor have been analyzed for potentials with different distances at which the retardation effects became effective. The retardation effects were found to break the otherwise long-range structural ordering occurring in strongly coupled dipolar fluids.
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77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
77.22.Ch Permittivity (dielectric function)
61.20.-p Structure of liquids

Carrier transport simulation in a model liquid crystalline system with the biaxial Gay–Berne potential

Masanao Goto, Hideo Takezoe, and Ken Ishikawa

J. Chem. Phys. 132, 054506 (2010); http://dx.doi.org/10.1063/1.3298506 (10 pages) | Cited 1 time

Online Publication Date: 3 February 2010

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In this paper, we performed carrier transport simulation to understand the unusual temperature dependence of the carrier mobility observed in nematic liquid crystals. For this purpose, we made a model liquid crystalline system consisting of biaxial Gay–Berne particles, and then we simulated hopping transport between these particles. The hopping rate was formulated suitably for the biaxial Gay–Berne particles based on the investigation of the electronic overlaps between actual aromatic molecules. The carrier transport simulation was performed by master equation method on the model system prepared by N-P-T ensemble Monte Carlo simulation. We reproduced gradual mobility increase in the nematic phase as a result of the change in the short range molecular order.
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61.30.-v Liquid crystals

The single donator-single acceptor hydrogen bonding structure in water probed by Raman spectroscopy

Qiang Sun

J. Chem. Phys. 132, 054507 (2010); http://dx.doi.org/10.1063/1.3308496 (4 pages) | Cited 2 times

Online Publication Date: 4 February 2010

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In this work, the Raman spectra of aqueous C12E5 solutions are recorded and utilized to demonstrate the existence of single donator-single acceptor (DA) hydrogen bonding in water. From Raman OH stretching bands of aqueous C12E5 solutions, the relative intensity of 3430 cm−1 subband increases with C12E5 concentrations. For confined water, the DA hydrogen bonding can be expected to be the important hydrogen bonding species. Therefore, the 3430 cm−1 component can be ascribed to OH vibration engaged in DA hydrogen bonding. This is in agreement with our recent explanation on Raman OH stretching band of water. For water at ambient conditions, the double donor-double acceptor (DDAA) and DA should be the dominant hydrogen bonding species, the ratio of DDAA to DA can be approximately to be 0.75:1, and the mean hydrogen bonding can be determined to be 2.75.
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33.20.Fb Raman and Rayleigh spectra (including optical scattering)
33.15.Fm Bond strengths, dissociation energies
33.20.Tp Vibrational analysis
34.70.+e Charge transfer
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