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22 Jun 2004

Volume 120, Issue 24, pp. 11347-11967

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Low-energy electron induced restructuring of water monolayers on NaCl(100)

J. P. Toennies, F. Traeger, J. Vogt, and H. Weiss

J. Chem. Phys. 120, 11347 (2004); http://dx.doi.org/10.1063/1.1763837 (4 pages) | Cited 15 times

Online Publication Date: 8 June 2004

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The influence of electron irradiation on the controversially discussed monolayer structure of H2O on NaCl(100) is investigated with helium atom diffraction before and after a low-damage low-energy electron diffraction (LEED) experiment. The ordered (1×1) structure observed initially with He atoms is found to be transformed to a stable c(4×2) structure after a 90 eV electron dosage of only 1015 electrons cm−2 or about 2 incident electrons per adsorbate molecule. Based on previously reported structure models for the two phases, the transition is attributed to a reorientation, and a possible compression of the water film induced by the electrons. © 2004 American Institute of Physics.
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68.08.De Liquid-solid interface structure: measurements and simulations
68.55.-a Thin film structure and morphology
68.49.Jk Electron scattering from surfaces

Proton transfer dynamics via high resolution spectroscopy in the gas phase and instanton calculations

Joseph R. Roscioli, David W. Pratt, Zorka Smedarchina, Willem Siebrand, and Antonio Fernández-Ramos

J. Chem. Phys. 120, 11351 (2004); http://dx.doi.org/10.1063/1.1751391 (4 pages) | Cited 13 times

Online Publication Date: 8 June 2004

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Tunneling splittings have been observed in the eigenstate-resolved electronic spectrum of the 2-hydroxypyridine/2-pyridone dimer in the gas phase. Deuterium substitution experiments show that these splittings are caused by a concerted double proton transfer reaction along the O–H⋯O and N⋯H–N hydrogen bonds that hold the dimer together, substitution of the weaker and longer N⋯H–N bond having the larger effect. Tunneling splittings calculated by the instanton method for the zero-point level of the ground state are in good agreement with experiment for all observed isotopomers, showing that the dynamics occurs in this state, rather than in the electronically excited state. © 2004 American Institute of Physics.
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82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)
82.20.Tr Kinetic isotope effects including muonium
33.15.Dj Interatomic distances and angles

Liquids confined in wedge shaped pores: Nonuniform pressure induced by pore geometry

Luis G. Cámara and Fernando Bresme

J. Chem. Phys. 120, 11355 (2004); http://dx.doi.org/10.1063/1.1764771 (4 pages) | Cited 5 times

Online Publication Date: 8 June 2004

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Lennard-Jones liquids confined in wedge shaped nanopores are investigated using molecular dynamics computer simulations. We show that small deviations from the parallel slit geometry result in nonuniform pressures and density profiles along the pore. In conditions of high confinement and thermodynamic states close to the triple point, wedge shaped pores can induce the formation of solid phases in specific regions within the nanopore. © 2004 American Institute of Physics.
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61.20.Ja Computer simulation of liquid structure
61.46.-w Structure of nanoscale materials
64.60.F- Equilibrium properties near critical points, critical exponents

Fragmentation dynamics of ionized neon trimer inside helium nanodroplets: A theoretical study

David Bonhommeau, Alexandra Viel, and Nadine Halberstadt

J. Chem. Phys. 120, 11359 (2004); http://dx.doi.org/10.1063/1.1763567 (4 pages) | Cited 11 times

Online Publication Date: 8 June 2004

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We report a theoretical study of the fragmentation dynamics of Ne3+ inside helium nanodroplets, following vertical ionization of the neutral neon trimer. The motion of the neon atoms is treated classically, while transitions between the electronic states of the ionic cluster are treated quantum mechanically. A diatomics-in-molecules description of the potential energy surfaces is used, in a minimal basis set consisting of three effective p orbitals on each neon atom for the missing electron. The helium environment is modeled by a friction force acting on the neon atoms when their speed exceeds the Landau velocity. A reasonable range of values for the corresponding friction coefficient is obtained by comparison with existing experimental measurements. © 2004 American Institute of Physics.
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36.40.Wa Charged clusters
33.15.Fm Bond strengths, dissociation energies
31.15.-p Calculations and mathematical techniques in atomic and molecular physics

Magic clusters MAu4 (M = Ti and Zr) and their dimers: How magic are they?

Tapan K. Ghanty, K. R. S. Chandrakumar, and Swapan K. Ghosh

J. Chem. Phys. 120, 11363 (2004); http://dx.doi.org/10.1063/1.1764494 (4 pages) | Cited 11 times

Online Publication Date: 8 June 2004

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The stability of closed shell bimetallic magic clusters MAu4 (M = Ti and Zr) is investigated theoretically through ab initio molecular orbital calculations. Both these clusters have tetrahedral structures and are found to be associated with large values of the ionization potential, HOMO-LUMO gap as well as the binding energies, which are characteristic of the magic clusters. However, the cluster–cluster interaction energy corresponding to a dimer formation is found to be unusually high ( ∼ 5–7 eV) in contradiction to the usual properties of a magic cluster and is attributed to a 3-center–2-electron M–Au–M type bridge bonding as well as aurophilic attraction. Gross geometrical features of the individual clusters are, however, mostly retained in the dimer, thus satisfying the basic requirements for the cluster-assembled materials. This work would have important implications in the design of novel cluster-based nanomaterials for various nanoscale applications.© 2004 American Institute of Physics.
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36.40.-c Atomic and molecular clusters
31.15.A- Ab initio calculations
33.15.Ry Ionization potentials, electron affinities, molecular core binding energy
33.15.Fm Bond strengths, dissociation energies
61.46.-w Structure of nanoscale materials

Mesoscopic chiral reshaping of the Ag(110) surface induced by the organic molecule PVBA

J. I. Pascual, J. V. Barth, G. Ceballos, G. Trimarchi, A. De Vita, K. Kern, and H.-P. Rust

J. Chem. Phys. 120, 11367 (2004); http://dx.doi.org/10.1063/1.1763836 (4 pages) | Cited 16 times

Online Publication Date: 8 June 2004

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We report scanning tunneling microscopy observations on the restructuring of a Ag(110) surface induced by the molecule 4-[trans-2-(pyrid-4-yl-vinyl)]benzoic acid (PVBA). Our data reveal that the surface undergoes a mesoscopic step faceting following exposure to submonolayer coverages and thermal activation. A sawtooth arrangement evolves implying long-range mass transport of substrate atoms and forming a regular arrangement of kink sites. Its formation is associated with the molecules’ functional headgroups forming carboxylates with {100} Ag microfacets at step edges, and eventually operating to reshape the surface morphology. Interestingly, the resulting microfacets act as chiral templates for the growth of supramolecular PVBA structures. Theoretical modeling based on ab initio results indicates that chiral recognition processes discriminating between the two enantiomers of adsorbed PVBA molecules occur in this process. © 2004 American Institute of Physics.
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68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.47.De Metallic surfaces

Vibronic states in single molecules: C60 and C70 on ultrathin Al2O3 films

N. Liu, N. A. Pradhan, and W. Ho

J. Chem. Phys. 120, 11371 (2004); http://dx.doi.org/10.1063/1.1765095 (5 pages) | Cited 14 times

Online Publication Date: 8 June 2004

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Vibronic states are observed in single C60 and C70 molecules by scanning tunneling microscopy. When single fullerene molecules are adsorbed on a thin layer of Al2O3 grown on a NiAl(110) substrate, equally spaced features are observed in the differential conductance (dI/dV), which are clearly resolved in d2I/dV2 spectra. These features are attributed to the vibronic states of the molecule. The vibronic progressions are sensitive to the molecular orientations and can have different spacings in different electronic bands of the same molecule. For C60, these vibronic states are associated with the intramolecular Ag and Hg vibrational modes. Vibronic states are not resolved in molecules adsorbed on the metal surface. However, inelastic electron tunneling spectroscopy exhibits a vibrational mode at 64 meV for C60 and 61 meV for C70 adsorbed on NiAl(110).© 2004 American Institute of Physics.
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33.20.Wr Vibronic, rovibronic, and rotation-electron-spin interactions
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.20.Tp Vibrational analysis

No evidence for large-scale proton ordering in Antarctic ice from powder neutron diffraction

A. D. Fortes, I. G. Wood, D. Grigoriev, M. Alfredsson, S. Kipfstuhl, K. S. Knight, and R. I. Smith

J. Chem. Phys. 120, 11376 (2004); http://dx.doi.org/10.1063/1.1765099 (4 pages) | Cited 9 times

Online Publication Date: 8 June 2004

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We have examined a sample of 3000 year old Antarctic ice, collected at the Kohnen Station, by time-of-flight powder neutron diffraction to test the hypothesis of Fukazawa et al. [e.g., Ann. Glaciol. 31, 247 (2000)] that such ice may be partially proton ordered. Great care was taken to keep our sample below the proposed ordering temperature (237 K) at all times, but we did not observe any evidence of proton ordering.© 2004 American Institute of Physics.
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64.70.K- Solid-solid transitions
61.05.fm Neutron diffraction
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back to top Theoretical Methods and Algorithms

An analysis of electronic dephasing in the spin-boson model

Hyonseok Hwang and Peter J. Rossky

J. Chem. Phys. 120, 11380 (2004); http://dx.doi.org/10.1063/1.1742979 (6 pages) | Cited 11 times

Online Publication Date: 8 June 2004

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In order to develop a more complete understanding of the limitations of mixed quantum-classical simulation methods, the origins of electronic dephasing are analyzed in a simple model of the condensed phase, namely, the spin-boson model with an ohmic spectral density. We focus on the decay of the thermally averaged nuclear overlap/phase function (NOPF). Considering the strong coupling/high temperature limit, a relationship is obtained at short time between the rate of electronic coherence loss and the electronic dephasing rate characteristic of a classical bath. Using this relationship, we clarify the origin of the decay of the NOPF. In the same limit, we also reproduce an earlier relationship between the electronic decoherence time and a solvation relaxation time. Finally, we point out that, for the spin-boson model, the exact quantum mechanical description of electronic dephasing is reproduced by mixed quantum/classical methods if a Gaussian distribution of quantum fluctuations around each classical phase space point is introduced. That spatial distribution of quantum fluctuations is functionally the same as that appearing in the Feynman–Kleinert variational local harmonic approximation, and also that implemented in existing classical trajectory-based estimates of coherence dissipation times. © 2004 American Institute of Physics.
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05.30.Jp Boson systems
03.75.Mn Multicomponent condensates; spinor condensates
02.50.Ng Distribution theory and Monte Carlo studies
03.65.Sq Semiclassical theories and applications

Theoretical method for full ab initio calculation of DNA/RNA–ligand interaction energy

Xi H. Chen and John Z. H. Zhang

J. Chem. Phys. 120, 11386 (2004); http://dx.doi.org/10.1063/1.1737295 (6 pages) | Cited 15 times

Online Publication Date: 8 June 2004

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In this paper, we further develop the molecular fractionation with conjugate caps (MFCC) scheme for quantum mechanical computation of DNA–ligand interaction energy. We study three oligonuclear acid interaction systems: dinucleotide dCG/water, trinucleotide dCGT/water, and a Watson–Crick paired DNA segment, dCGT/dGCA. Using the basic MFCC approach, the nucleotide chains are cut at each phosphate group and a pair of conjugate caps (concaps) are inserted. Five cap molecules have been tested among which the dimethyl phosphate anion is proposed to be the standard concap for application. For each system, one-dimensional interaction potential curves are computed using the MFCC method and the calculated interaction energies are found to be in excellent agreement with corresponding results obtained from the full system ab initio calculations. The current study extends the application of the MFCC method to ab initio calculations for DNA– or RNA–ligand interaction energies. © 2004 American Institute of Physics.
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31.15.A- Ab initio calculations
36.20.Fz Constitution (chains and sequences)
87.15.H- Dynamics of biomolecules
87.15.K- Molecular interactions; membrane-protein interactions
34.20.-b Interatomic and intermolecular potentials and forces, potential energy surfaces for collisions
33.15.Fm Bond strengths, dissociation energies

Fast semiempirical calculations for nuclear magnetic resonance chemical shifts: A divide-and-conquer approach

Bing Wang, Edward N. Brothers, Arjan van der Vaart, and Kenneth M. Merz

J. Chem. Phys. 120, 11392 (2004); http://dx.doi.org/10.1063/1.1752877 (9 pages) | Cited 8 times

Online Publication Date: 8 June 2004

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A new approach to calculate nuclear magnetic resonance chemical shifts has been implemented at the semiempirical modified neglect of diatomic overlap level using gauge-including atomic orbitals. The perturbed density matrix with respect to the magnetic field is obtained by the diagonalization of the complex Fock matrix using the divide and conquer (DC) method, instead of by solving the computationally expensive coupled perturbed Hartree–Fock equations. Adopting the Patchkovskii and Thiel parameters [S. Patchkovskii and W. Thiel J. Comput. Chem. 20, 1220 (1999)], we were able to reproduce their results for small organic molecules. The errors introduced by DC method are negligible, as shown by the calculations on a series of polyalaine structures. Test calculations on proteins have demonstrated that our approach makes it possible to calculate chemical shifts routinely on systems with hundreds of atoms with good accuracy. © 2004 American Institute of Physics.
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33.25.+k Nuclear resonance and relaxation
82.56.Pp NMR of biomolecules
31.15.bu Semi-empirical and empirical calculations (differential overlap, Hückel, PPP methods, etc.)

An adaptive immune optimization algorithm for energy minimization problems

Xueguang Shao, Longjiu Cheng, and Wensheng Cai

J. Chem. Phys. 120, 11401 (2004); http://dx.doi.org/10.1063/1.1753257 (6 pages) | Cited 18 times

Online Publication Date: 8 June 2004

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Based on the immune theory of biology, a novel evolutionary algorithm, adaptive immune optimization algorithm (AIOA), is proposed. In AIOA, density regulation and immune selection is adopted to control the individual diversity and the convergence adaptively. By an application of the algorithm to the optimization of test functions, it is shown that the algorithm is a highly efficient optimization method compared with other stochastic optimization methods. The algorithm was also applied to the optimization of Lennard-Jones clusters, and the results show that the method can find the optimal structure of N ⩽ 80 with a very high efficiency. The proposed algorithm may be a good tool for fast global optimization in chemical or biological molecular simulations. © 2004 American Institute of Physics.
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87.23.Kg Dynamics of evolution

Calculation of indirect nuclear spin–spin coupling constants within the regular approximation for relativistic effects

Michael Filatov and Dieter Cremer

J. Chem. Phys. 120, 11407 (2004); http://dx.doi.org/10.1063/1.1752876 (16 pages) | Cited 23 times

Online Publication Date: 8 June 2004

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A new method for calculating the indirect nuclear spin–spin coupling constant within the regular approximation to the exact relativistic Hamiltonian is presented. The method is completely analytic in the sense that it does not employ numeric integration for the evaluation of relativistic corrections to the molecular Hamiltonian. It can be applied at the level of conventional wave function theory or density functional theory. In the latter case, both pure and hybrid density functionals can be used for the calculation of the quasirelativistic spin–spin coupling constants. The new method is used in connection with the infinite-order regular approximation with modified metric (IORAmm) to calculate the spin–spin coupling constants for molecules containing heavy elements. The importance of including exact exchange into the density functional calculations is demonstrated. © 2004 American Institute of Physics.
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31.30.J- Relativistic and quantum electrodynamic (QED) effects in atoms, molecules, and ions
33.15.-e Properties of molecules

An efficient atomic orbital based second-order Møller–Plesset gradient program

Svein Saebø, Jon Baker, Krzysztof Wolinski, and Peter Pulay

J. Chem. Phys. 120, 11423 (2004); http://dx.doi.org/10.1063/1.1752880 (9 pages) | Cited 11 times

Online Publication Date: 8 June 2004

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Based on the orbital-invariant atomic orbital formulation of the MP2 (Møller–Plesset second-order perturbation theory) energy and gradient [P. Pulay and S. Saebø, Theor. Chim. Acta 69, 357 (1986)], we have derived and programmed detailed working equations for closed-shell MP2 gradients. The orbital-invariant form avoids the difficulties of other formulations with frozen orbitals, and allows the use of arbitrary occupied orbitals, an important consideration for local correlation theories, although the present program uses canonical molecular orbitals. The atomic orbital formulation offers savings both in storage and computer time. Test calculations on systems containing up to ∼100 atoms and ∼1000 basis functions, performed on a single personal computer, are reported. Parallelization of the code is underway. © 2004 American Institute of Physics.
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31.15.xp Perturbation theory
31.10.+z Theory of electronic structure, electronic transitions, and chemical binding

Langevin dynamics in constant pressure extended systems

D. Quigley and M. I. J. Probert

J. Chem. Phys. 120, 11432 (2004); http://dx.doi.org/10.1063/1.1755657 (10 pages) | Cited 18 times

Online Publication Date: 8 June 2004

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The advantages of performing Langevin dynamics in extended systems are discussed. A simple Langevin dynamics scheme for producing the canonical ensemble is reviewed, and is then extended to the Hoover ensemble. We show that the resulting equations of motion generate the isobaric–isothermal ensemble. The Parrinello–Rahman ensemble is then discussed and we show that despite the presence of intrinsic probability gradients in this system, a Langevin dynamics approach samples the extended phase space in the correct fashion. The implementation of these methods in the ab initio plane wave density functional theory code CASTEP [M. D. Segall, P. L. D. Lindan, M. J. Probert, C. J. Pickard, P. J. Hasnip, S. J. Clarke, and M. C. Payne, J. Phys.: Condens. Matter 14, 2717 (2003)] is demonstrated. © 2004 American Institute of Physics.
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31.15.E- Density-functional theory
31.15.A- Ab initio calculations
01.30.Rr Surveys and tutorial papers; resource letters
02.30.Hq Ordinary differential equations

Quantum pathways for resonance energy transfer

Robert D. Jenkins, Gareth J. Daniels, and David L. Andrews

J. Chem. Phys. 120, 11442 (2004); http://dx.doi.org/10.1063/1.1742697 (7 pages) | Cited 11 times

Online Publication Date: 8 June 2004

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A quantum electrodynamical calculation is presented that focuses individually on the two quantum pathways or time orderings for resonance energy transfer. Conventional mathematical procedures necessitate summing the quantum pathway amplitudes at an early stage in the calculations. Here it is shown, by the adoption of a different strategy that allows deferral of the amplitude summation, that it is possible to elicit key information regarding the relative significance of the two pathways and their distinct distance dependences. A special function integration method delivers equations that also afford new insights into the behavior of virtual photons. It is explicitly demonstrated that both time-ordered pathways are effective at short distances, while in the far field the dissipation of virtual traits favors one pathway. Hitherto unknown features are exhibited in the oblique asymptotic behavior of the time-ordered contributions and their quantum interference. Consistency with the rate equations of resonance energy transfer is demonstrated and results are presented graphically. © 2004 American Institute of Physics.
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31.30.J- Relativistic and quantum electrodynamic (QED) effects in atoms, molecules, and ions
34.20.Gj Intermolecular and atom-molecule potentials and forces
03.65.-w Quantum mechanics
02.30.Cj Measure and integration

Intermediate state representation approach to physical properties of electronically excited molecules

J. Schirmer and A. B. Trofimov

J. Chem. Phys. 120, 11449 (2004); http://dx.doi.org/10.1063/1.1752875 (16 pages) | Cited 30 times

Online Publication Date: 8 June 2004

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Propagator methods provide a direct approach to energies and transition moments for (generalized) electronic excitations from the ground state, but they do not usually allow one to determine excited state wave functions and properties. Using a specific intermediate state representation (ISR) concept, we here show how this restriction can be overcome in the case of the algebraic–diagrammatic construction (ADC) propagator approach. In the ISR reformulation of the theory the basic ADC secular matrix is written as a representation of the Hamiltonian (or the shifted Hamiltonian) in terms of explicitly constructable states, referred to as intermediate (or ADC) states. Similar intermediate state representations can be derived for operators other than the Hamiltonian. Together with the ADC eigenvectors, the intermediate states give rise to an explicit formulation of the excited wave functions and allow one to calculate physical properties of excited states as well as transition moments for transitions between different excited states. As for the ground-state excitation energies and transition moments, the ADC excited state properties are size consistent so that the theory is suitable for applications to large systems. The established hierarchy of higher-order [ADC(n)] approximations, corresponding to systematic truncations of the IS configuration space and the perturbation–theoretical expansions of the ISR matrix elements, can readily be extended to the excited state properties. Explicit ISR matrix elements for arbitrary one-particle operators have been derived and coded at the second-order [ADC(2)] level of theory. As a first computational test of the method we have carried out ADC(2) calculations for singlet and triplet excited state dipole moments in H2O and HF, where comparison to full CI results can be made. The potential of the ADC(2) method is further demonstrated in an exploratory study of the excitation energies and dipole moments of the low-lying excited states of paranitroaniline. We find that four triplet states, T1–T4, and two singlet states, S1 and S2, lie (vertically) below the prominent charge transfer (CT) excitation, S3. The dipole moment of the S3 state (17.0D) is distinctly larger than that of the corresponding T3 triplet state (11.7D).© 2004 American Institute of Physics.
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33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility
34.70.+e Charge transfer
back to top Gas Phase Dynamics and Structure: Spectroscopy, Molecular Interactions, Scattering, and Photochemistry

The anomalous shape of the cross section for the formation of SF3+ fragment ions produced by electron impact on SF6 revisited

S. Feil, K. Gluch, P. Scheier, K. Becker, and T. D. Märk

J. Chem. Phys. 120, 11465 (2004); http://dx.doi.org/10.1063/1.1753553 (4 pages) | Cited 5 times

Online Publication Date: 8 June 2004

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The partial ionization cross section for the formation of SF3+ fragment ions following electron impact on SF6 is known to have a pronounced structure in the cross section curve slightly above 40 eV. We used the mass-analyzed ion kinetic energy (MIKE) scan technique to demonstrate the presence of a channel contributing to the SF3+ partial ionization cross section that we attribute to the Coulomb explosion of doubly charged metastable SF42+ ions into two singly charged ions SF3+ and F+, with a threshold energy of about 45.5 eV. Thus the observed unusual shape of the SF3+ partial ionization cross section is the result of two contributions, (i) the direct formation of SF3+ fragment ions via dissociative ionization of SF6 with a threshold energy of 22 eV and (ii) the Coulomb explosion of metastable SF42+ ions with a threshold energy of about 45.5 eV. A detailed analysis of the MIKE spectrum reveals an average kinetic energy release of about 5 eV in the Coulomb explosion of the SF42+ ions with evidence of a second channel corresponding to an average kinetic energy release of about 1.1 eV. © 2004 American Institute of Physics.
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34.80.Gs Molecular excitation and ionization
34.80.Ht Dissociation and dissociative attachment
33.15.Fm Bond strengths, dissociation energies
01.30.Rr Surveys and tutorial papers; resource letters

Characteristics and relaxation dynamics of van der Waals complexes between p-difluorobenzene and Ne

Thankan Jayasekharan and Charles S. Parmenter

J. Chem. Phys. 120, 11469 (2004); http://dx.doi.org/10.1063/1.1747847 (10 pages) | Cited 4 times

Online Publication Date: 8 June 2004

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Characteristics of the single and double Ne van der Waals complexes of p-difluorobenzene (pDFB) have been explored with ultraviolet fluorescence excitation and dispersed fluorescence spectroscopy. Eight S1–S0 fluorescence excitation bands involving six ring modes of pDFB–Ne and two bands of pDFB–Ne2 have been identified. Band assignments are confirmed by dispersed fluorescence from the pumped band. Shifts of the complex bands from the analogous monomer bands are generally 4 cm−1 to the red for pDFB–Ne and 8 cm−1 for pDFB–Ne2. None of the observed ring modes is significantly perturbed by complexation in either the S1 or S0 states. The pDFB–Ne S1 van der Waals binding energy D0′ ⩽ 120 cm−1 is inferred from fluorescence band assignments with D0′−D0″ = 4 cm−1. Vibrational predissociation of pDFB–Ne to produce the S1 monomer is observed after pumping several levels, but the dissociation process is generally slow compared to fluorescence decay of the complex. Dissociation of the double complex pDFB–Ne2 occurs from one level to produce S1 pDFB–Ne in its zero point level. Comparisons are made with the relaxation dynamics of the S1 complexes pDFB–Ar and pDFB–N2. © 2004 American Institute of Physics.
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33.50.Dq Fluorescence and phosphorescence spectra
33.20.Lg Ultraviolet spectra
33.15.Hp Barrier heights (internal rotation, inversion, rotational isomerism, conformational dynamics)
33.70.Jg Line and band widths, shapes, and shifts
33.80.Gj Diffuse spectra; predissociation, photodissociation
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.20.Tp Vibrational analysis
33.15.Ry Ionization potentials, electron affinities, molecular core binding energy

Distributed polarizability analysis for para-nitroaniline and meta-nitroaniline: Functional group and charge-transfer contributions

M. in het Panhuis, R. W. Munn, and P. L. A. Popelier

J. Chem. Phys. 120, 11479 (2004); http://dx.doi.org/10.1063/1.1752879 (8 pages) | Cited 2 times

Online Publication Date: 8 June 2004

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Topological partitioning of electronic properties is used to investigate the polarizability of para-nitroaniline and meta-nitroaniline. The distributed polarizabilities for atoms are combined into total local or generalized distributed contributions for the amino, ring, and nitro functional groups; generalized distributed group contributions have not been calculated before. The local group contributions are transferable between the two molecules only when charge transfer is suppressed, but the generalized distributed contributions prove surprisingly similar in the two molecules, apparently because they treat charge-transfer contributions explicitly. © 2004 American Institute of Physics.
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33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility
31.15.-p Calculations and mathematical techniques in atomic and molecular physics

Metallophilic attractions between d8–d10 heterometallic compounds trans-[Pt(PH3)2(CN)2] and M(PH3)2+ (M = Ag or Cu): Ab initio study

Bao-Hui Xia, Hong-Xing Zhang, Yu-Qiu Jiao, Qing-Jiang Pan, Ze-Sheng Li, and Chia-Chung Sun

J. Chem. Phys. 120, 11487 (2004); http://dx.doi.org/10.1063/1.1753563 (6 pages) | Cited 4 times

Online Publication Date: 8 June 2004

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The weak metal–metal interactions of Pt(II)–Ag(I)/Cu(I) have been investigated by ab initio method at MP2 level through the model complexes [trans-Pt(PH3)2(CN)2-M(PH3)2+] (M = Ag,Cu). The calculated interaction energy of 12.9 and 11.5 kcal mol−1 for [trans-Pt(PH3)2(CN)2-Ag(PH3)2+] and [trans-Pt(PH3)2(CN)2–Cu(PH3)2+] respectively, are in the middle of the van der Waals force and the strong hydrogen bond. The estimated equilibrium separations between Pt and M, req(Pt–M) (3.32 Å for M = Ag and 3.23 Å for M = Cu), lie within the region expected for weak metal–metal interaction. The electronic dispersive contributions dominate the weak interaction. © 2004 American Institute of Physics.
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33.15.Fm Bond strengths, dissociation energies
31.15.vq Electron correlation calculations for polyatomic molecules

Calculations on the octupolar molecules with enhanced two-photon absorption cross sections based on the Zn (II) and Cu (I) as centers

Xiao-Juan Liu, Ji-Kang Feng, Ai-Min Ren, Hong Cheng, and Xin Zhou

J. Chem. Phys. 120, 11493 (2004); http://dx.doi.org/10.1063/1.1742861 (7 pages) | Cited 14 times

Online Publication Date: 8 June 2004

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The equilibrium geometries, electronic structures, as well as one- and two-photon absorption cross sections of a series of octupolar chromophores with Zn2+ or Cu+ as coordinate centers and 4,4′-bis(dibutylaminostyryl)-[2,2′]-bis(bipyridyl) as ligands have been determined by using B3LYP/6-31G and ZINDO methods. These molecules are designed by controlled combination of two or three bipyridyl ligands with the metal centers. The results show that Zn2+ is an effective template for the design of octupolar structures which enable it to form tetrahedral and octahedral coordinated complexes; while Cu+ only exists in a tetrahedral coordinated complex, comparing the tetrahedral complex with Zn2+ as the center with that of Cu+ as the center, it is found that the complex with the Cu+ center is a better two-photon absorption material than the former as far as the transparency/nonlinearity is concerned. Furthermore, for the same metal center of Zn2+, both one- and two-photon absorptions of the tetrahedral complex are redshifted relative to those of the octahedral complex, is attributed to the spiroconjugation effect in the tetrahedral complex. Our theoretical findings are consistent with recent experimental observations and provide an important foundation for the design of improved transparency-nonlinearity two-photon absorption materials. © 2004 American Institute of Physics.
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33.80.Wz Other multiphoton processes
33.15.Bh General molecular conformation and symmetry; stereochemistry

Ab initio investigation of the ground and low-lying states of the diatomic fluorides TiF, VF, CrF, and MnF

Constantine Koukounas, Stavros Kardahakis, and Aristides Mavridis

J. Chem. Phys. 120, 11500 (2004); http://dx.doi.org/10.1063/1.1738412 (22 pages) | Cited 14 times

Online Publication Date: 8 June 2004

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The electronic structure of the ground and low-lying states of the diatomic fluorides TiF, VF, CrF, and MnF was examined by multireference and coupled cluster methods in conjunction with extended basis sets. For a total of 34 states we report binding energies, spectroscopic constants, dipole moments, separation energies, and charge distributions. In addition, for all states we have constructed full potential curves. The suggested ground state binding energies of TiF(X 4Φ), VF(X 5Π), CrF(X 6Σ+), and MnF(X 7Σ+) are 135, 130, 110, and 108 kcal/mol, respectively, with first excited states A 4Σ−, A 5Δ, A 6Π, and a 5Σ+ about 2, 3, 23, and 19 kcal/mol higher. In essence all our numerical findings are in harmony with experimental results. For all molecules and states studied it is clear that the in situ metal atom (M) shows highly ionic character, therefore the binding is described realistically by M+F−. © 2004 American Institute of Physics.
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31.15.A- Ab initio calculations
31.50.Bc Potential energy surfaces for ground electronic states
31.50.Df Potential energy surfaces for excited electronic states
31.15.bw Coupled-cluster theory
33.15.Ry Ionization potentials, electron affinities, molecular core binding energy
33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility

Coherent spin control of matrix isolated molecules by IR+UV laser pulses: Quantum simulations for ClF in Ar

M. V. Korolkov and J. Manz

J. Chem. Phys. 120, 11522 (2004); http://dx.doi.org/10.1063/1.1753256 (10 pages) | Cited 15 times

Online Publication Date: 8 June 2004

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Two coherent sequential IR+UV laser pulses may be used to generate two time-dependent nuclear wave functions in electronic excited triplet and singlet states via single (UV) and two photon (IR+UV) excitation pathways, exploiting spin–orbit coupling and vibrational pre-excitation, respectively. These wave functions evolve from different Franck–Condon domains until they overlap in a domain of bond stretching with efficient intersystem crossing. Here, the coherence of the laser pulses is turned into optimal interferences of the wave packets, yielding the total wave packet at the target place, time, and with dominant target spin. The time resolution of spin control is few femtoseconds. The mechanism is demonstrated by means of quantum model simulations for ClF in an Ar matrix. © 2004 American Institute of Physics.
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33.20.Ea Infrared spectra
33.20.Lg Ultraviolet spectra
33.80.-b Photon interactions with molecules
33.70.Ca Oscillator and band strengths, lifetimes, transition moments, and Franck-Condon factors
33.15.Fm Bond strengths, dissociation energies

Molecular isomerization induced by ultrashort infrared pulses. I. Few-cycle to sub-one-cycle Gaussian pulses and the role of the carrier-envelope phase

Christoph Uiberacker and Werner Jakubetz

J. Chem. Phys. 120, 11532 (2004); http://dx.doi.org/10.1063/1.1753260 (8 pages) | Cited 20 times

Online Publication Date: 8 June 2004

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Using 550 previously calculated vibrational energy levels and dipole moments we performed simulations of the HCN→HNC isomerization dynamics induced by sub-one-cycle and few-cycle IR pulses, which we represent as Gaussian pulses with 0.25–2 optical cycles in the pulse width. Starting from vibrationally pre-excited states, isomerization probabilities of up to 50% are obtained for optimized pulses. With decreasing number of optical cycles a strong dependence on the carrier-envelope phase (CEP) emerges. Although the optimized pulse parameters change significantly with the number of optical cycles, the distortion by the Gaussian envelope produces nearly equal fields, with a positive lobe followed by a negative one. The positions and areas of the lobes are also almost unchanged, irrespective of the number of cycles in the half-width. Isomerization proceeds via a pump–dumplike mechanism induced by the sequential lobes. The first lobe prepares a wave packet incorporating many delocalized states above the barrier. It is the motion of this wave packet across the barrier, which determines the timing of the pump and dump lobes. The role of the pulse parameters, and in particular of the CEP, is to produce the correct lobe sequence, size and timing within a continuous pulse. © 2004 American Institute of Physics.
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82.30.Qt Isomerization and rearrangement
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility
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