JCP Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

You Tube Flickr Twitter UniPHY Group iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

21 Mar 2011

Volume 134, Issue 11, Articles (11xxxx)

Issue Cover Spotlight Figure

J. Chem. Phys. 134, 114501 (2011); http://dx.doi.org/10.1063/1.3559153 (6 pages)

Ulf R. Pedersen, Toby S. Hudson, and Peter Harrowell
Enlarge Image | Read More
Page 1 of 3 Pages Next Page | Jump to Page
back to top
RSS Feeds
back to top Theoretical Methods and Algorithms

Direct correlation function for complex square barrier-square well potentials in the first-order mean spherical approximation

S. P. Hlushak, A. D. Trokhymchuk, and S. Sokołowski

J. Chem. Phys. 134, 114101 (2011); http://dx.doi.org/10.1063/1.3560049 (10 pages)

Online Publication Date: 15 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The direct correlation function of the complex discrete potential model fluids is obtained as a linear combination of the first-order mean spherical approximation (FMSA) solution for the simple square well model that has been reported recently [Hlushak et al., J. Chem. Phys. 130, 234511 (2009)]. The theory is employed to evaluate the structure and thermodynamics of complex fluids based on the square well-barrier and square well-barrier-well discrete potential models. Obtained results are compared with theoretical predictions of the hybrid mean spherical approximation, already reported in the literature [Guillen-Escamilla et al., J. Phys.: Condens. Matter 19, 086224 (2007)], and with computer simulation data of this study. The compressibility route to thermodynamics is then used to check whether the FMSA theory is able to predict multiple fluid–fluid transitions for the square barrier-well model fluids.
Show PACS
61.20.Gy Theory and models of liquid structure
65.20.De General theory of thermodynamic properties of liquids, including computer simulation

An orbital-invariant internally contracted multireference coupled cluster approach

Francesco A. Evangelista and Jürgen Gauss

J. Chem. Phys. 134, 114102 (2011); http://dx.doi.org/10.1063/1.3559149 (15 pages) | Cited 10 times

Online Publication Date: 16 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have formulated and implemented an internally contracted multireference coupled cluster (ic-MRCC) approach aimed at solving two of the problems encountered in methods based on the Jeziorski–Monkhorst ansatz: (i) the scaling of the computational and memory costs with respect to the number of references, and (ii) the lack of invariance of the energy with respect to rotations among active orbitals. The ic-MRCC approach is based on a straightforward generalization of the single-reference coupled cluster ansatz in which an exponential operator is applied to a multiconfigurational wave function. The ic-MRCC method truncated to single and double excitations (ic-MRCCSD) yields very accurate potential energy curves in benchmark computations on the Be + H2 insertion reaction, the dissociation of hydrogen fluoride, and the symmetric double dissociation of water. Approximations of the ic-MRCC theory in which the Baker–Campbell–Hausdorff expansion is truncated up to a given number of commutators are found to converge quickly to the full theory. In our tests, two commutators are sufficient to recover a total energy within 0.5 mEh of the full ic-MRCCSD method along the entire potential energy curve. A formal analysis shows that the ic-MRCC method is invariant with respect to rotation among active orbitals, and that the orthogonalization procedure used to produce the set of linearly independent excitation operators plays a crucial role in guaranteeing the invariance properties. The orbital invariance was confirmed in numerical tests. Moreover, approximated versions of the ic-MRCC theory based on a truncated Baker–Campbell–Hausdorff expansion, preserve the orbital invariance properties of the full theory.
Show PACS
31.15.bw Coupled-cluster theory
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
82.20.Kh Potential energy surfaces for chemical reactions
82.20.Wt Computational modeling; simulation

Semiclassical instanton approach to calculation of reaction rate constants in multidimensional chemical systems

Maksym Kryvohuz

J. Chem. Phys. 134, 114103 (2011); http://dx.doi.org/10.1063/1.3565425 (17 pages) | Cited 3 times

Online Publication Date: 17 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The semiclassical instanton approximation is revisited in the context of its application to the calculation of chemical reaction rate constants. An analytical expression for the quantum canonical reaction rate constants of multidimensional systems is derived for all temperatures from the deep tunneling to high-temperature regimes. The connection of the derived semiclassical instanton theory with several previously developed reaction rate theories is shown and the numerical procedure for the search of instanton trajectories is provided. The theory is tested on seven different collinear symmetric and asymmetric atom transfer reactions including heavy-light-heavy, light-heavy-light and light-light-heavy systems. The obtained thermal rate constants agree within a factor of 1.5–2 with the exact quantum results in the wide range of temperatures from 200 to 1500 K.
Show PACS
82.20.Pm Rate constants, reaction cross sections, and activation energies
82.20.Ej Quantum theory of reaction cross section
82.20.Fd Collision theories; trajectory models
82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)
82.20.Ln Semiclassical theory of reactions and/or energy transfer

On the equivalence of two commonly used forms of semiclassical instanton theory

Stuart C. Althorpe

J. Chem. Phys. 134, 114104 (2011); http://dx.doi.org/10.1063/1.3563045 (8 pages) | Cited 5 times

Online Publication Date: 17 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Semiclassical instanton theory gives an approximate description of deep tunneling by means of periodic orbits on the inverted potential energy surface. There are two versions of the theory, one derived by taking a semiclassical limit of the exact flux-side time-correlation function and the other by starting from the “Im F” premise, in which the partition function is analytically continued into the complex plane. Here, we provide a derivation showing that the two versions of the theory are exactly equivalent. Unlike a previous derivation (which was restricted to a system-bath model), our derivation is completely general, and thus establishes that the “Im F” premise, which is behind such methods as quantum transition-state theory and ring polymer molecular dynamics rate-theory, is correct in the steepest-descent limit.
Show PACS
31.15.xv Molecular dynamics and other numerical methods
31.50.-x Potential energy surfaces

Reducing experimental variability in variance-based sensitivity analysis of biochemical reaction systems

Hong-Xuan Zhang and John Goutsias

J. Chem. Phys. 134, 114105 (2011); http://dx.doi.org/10.1063/1.3563539 (16 pages)

Online Publication Date: 17 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Sensitivity analysis is a valuable task for assessing the effects of biological variability on cellular behavior. Available techniques require knowledge of nominal parameter values, which cannot be determined accurately due to experimental uncertainty typical to problems of systems biology. As a consequence, the practical use of existing sensitivity analysis techniques may be seriously hampered by the effects of unpredictable experimental variability. To address this problem, we propose here a probabilistic approach to sensitivity analysis of biochemical reaction systems that explicitly models experimental variability and effectively reduces the impact of this type of uncertainty on the results. The proposed approach employs a recently introduced variance-based method to sensitivity analysis of biochemical reaction systems [Zhang et al., J. Chem. Phys. 134, 094101 (2009)] and leads to a technique that can be effectively used to accommodate appreciable levels of experimental variability. We discuss three numerical techniques for evaluating the sensitivity indices associated with the new method, which include Monte Carlo estimation, derivative approximation, and dimensionality reduction based on orthonormal Hermite approximation. By employing a computational model of the epidermal growth factor receptor signaling pathway, we demonstrate that the proposed technique can greatly reduce the effect of experimental variability on variance-based sensitivity analysis results. We expect that, in cases of appreciable experimental variability, the new method can lead to substantial improvements over existing sensitivity analysis techniques.
Show PACS
87.15.R- Reactions and kinetics
82.20.Db Transition state theory and statistical theories of rate constants
87.17.-d Cell processes

Dispersion interaction in hydrogen-chain models

Ru-Fen Liu, János G. Ángyán, and John F. Dobson

J. Chem. Phys. 134, 114106 (2011); http://dx.doi.org/10.1063/1.3563596 (8 pages) | Cited 1 time

Online Publication Date: 17 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have investigated the dispersion interaction in hydrogen chain models via density functional theory-based symmetry-adapted perturbation theory using the asymptotically corrected PBE0 energy functional. The quasimetallic and the insulating prototype systems were chosen to be hydrogen chains with equally and alternately spaced H2 units, respectively. The dependence of the dispersion energy on the chain length for quasimetallic and insulating cases has been determined for two chains arranged either in pointing or in parallel geometries. The results are compared with those previously calculated from a continuum coupled-plasmon approach [Phys. Rev. B 77, 075436 (2008)]. The interaction energy has also been modeled by pairwise summations over short fragments of the chains, demonstrating the failure of the additivity principle for the quasimetallic case, while confirming that the additivity is a qualitatively reasonable hypothesis for the insulating case.
Show PACS
31.15.E- Density-functional theory
31.15.xp Perturbation theory
33.15.Bh General molecular conformation and symmetry; stereochemistry
33.15.Fm Bond strengths, dissociation energies
FREE

Catalytic conversion reactions mediated by single-file diffusion in linear nanopores: Hydrodynamic versus stochastic behavior

David M. Ackerman, Jing Wang, Joseph H. Wendel, Da-Jiang Liu, Marek Pruski, and James W. Evans

J. Chem. Phys. 134, 114107 (2011); http://dx.doi.org/10.1063/1.3563638 (13 pages) | Cited 1 time

Online Publication Date: 17 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We analyze the spatiotemporal behavior of species concentrations in a diffusion-mediated conversion reaction which occurs at catalytic sites within linear pores of nanometer diameter. Diffusion within the pores is subject to a strict single-file (no passing) constraint. Both transient and steady-state behavior is precisely characterized by kinetic Monte Carlo simulations of a spatially discrete lattice–gas model for this reaction–diffusion process considering various distributions of catalytic sites. Exact hierarchical master equations can also be developed for this model. Their analysis, after application of mean-field type truncation approximations, produces discrete reaction–diffusion type equations (mf-RDE). For slowly varying concentrations, we further develop coarse-grained continuum hydrodynamic reaction–diffusion equations (h-RDE) incorporating a precise treatment of single-file diffusion in this multispecies system. The h-RDE successfully describe nontrivial aspects of transient behavior, in contrast to the mf-RDE, and also correctly capture unreactive steady-state behavior in the pore interior. However, steady-state reactivity, which is localized near the pore ends when those regions are catalytic, is controlled by fluctuations not incorporated into the hydrodynamic treatment. The mf-RDE partly capture these fluctuation effects, but cannot describe scaling behavior of the reactivity.
Show PACS
82.40.Ck Pattern formation in reactions with diffusion, flow and heat transfer
82.45.Jn Surface structure, reactivity and catalysis
82.40.Np Temporal and spatial patterns in surface reactions
82.20.Uv Stochastic theories of rate constants
61.43.Gt Powders, porous materials

Multireference coupled-cluster theory: The easy way

Monika Musiał, Ajith Perera, and Rodney J. Bartlett

J. Chem. Phys. 134, 114108 (2011); http://dx.doi.org/10.1063/1.3567115 (10 pages) | Cited 11 times

Online Publication Date: 18 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The multi-ionization equation-of-motion coupled-cluster (CC) method is developed for multireference (MR) problems. It is operationally single reference, depending upon a formal matrix diagonalization step to define the coefficients in the wavefunction in an unbiased way that allows for important MR character. The method is illustrated for the autoisomerization of cyclobutadiene, which has a very large multireference effect and compared to other MR-CC results. The newly implemented methods are also used to obtain the vertical double ionization (DI) potentials of several small molecules (H2O, CO, C2H2, C2H4). Also, the performance of the new methods is analyzed by plotting the potential energy curve for twisted ethylene as a function of a dihedral angle between two methylenes. Evaluation of the total molecular energy via MR-DI-CC calculations makes it possible to avoid an unphysical cusp.
Show PACS
33.80.Eh Autoionization, photoionization, and photodetachment
33.15.Ry Ionization potentials, electron affinities, molecular core binding energy
31.50.-x Potential energy surfaces
31.15.bw Coupled-cluster theory

Interaction between LiH molecule and Li atom from state-of-the-art electronic structure calculations

Wojciech Skomorowski, Filip Pawłowski, Tatiana Korona, Robert Moszynski, Piotr S. Żuchowski, and Jeremy M. Hutson

J. Chem. Phys. 134, 114109 (2011); http://dx.doi.org/10.1063/1.3563613 (16 pages) | Cited 8 times

Online Publication Date: 18 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
State-of-the-art ab initio techniques have been applied to compute the potential energy surface for the lithium atom interacting with the lithium hydride molecule in the Born–Oppenheimer approximation. The interaction potential was obtained using a combination of the explicitly correlated unrestricted coupled-cluster method with single, double, and noniterative triple excitations [UCCSD(T)-F12] for the core–core and core–valence correlation and full configuration interaction for the valence–valence correlation. The potential energy surface has a global minimum 8743 cm−1 deep if the Li–H bond length is held fixed at the monomer equilibrium distance or 8825 cm−1 deep if it is allowed to vary. In order to evaluate the performance of the conventional CCSD(T) approach, calculations were carried out using correlation-consistent polarized valence X-tuple-zeta basis sets, with X ranging from 2 to 5, and a very large set of bond functions. Using simple two-point extrapolations based on the single-power laws X−2 and X−3 for the orbital basis sets, we were able to reproduce the CCSD(T)–F12 results for the characteristic points of the potential with an error of 0.49% at worst. The contribution beyond the CCSD(T)–F12 model, obtained from full configuration interaction calculations for the valence–valence correlation, was shown to be very small, and the error bars on the potential were estimated. At linear LiH–Li geometries, the ground-state potential shows an avoided crossing with an ion-pair potential. The energy difference between the ground-state and excited-state potentials at the avoided crossing is only 94 cm−1. Using both adiabatic and diabatic pictures, we analyze the interaction between the two potential energy surfaces and its possible impact on the collisional dynamics. When the Li–H bond is allowed to vary, a seam of conical intersections appears at C2v geometries. At the linear LiH–Li geometry, the conical intersection is at a Li–H distance which is only slightly larger than the monomer equilibrium distance, but for nonlinear geometries it quickly shifts to Li–H distances that are well outside the classical turning points of the ground-state potential of LiH. This suggests that the conical intersection will have little impact on the dynamics of Li–LiH collisions at ultralow temperatures. Finally, the reaction channels for the exchange and insertion reactions are also analyzed and found to be unimportant for the dynamics.
Show PACS
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)
82.30.Nr Association, addition, insertion, cluster formation
82.20.Kh Potential energy surfaces for chemical reactions

A simple but fully nonlocal correction to the random phase approximation

Adrienn Ruzsinszky, John P. Perdew, and Gábor I. Csonka

J. Chem. Phys. 134, 114110 (2011); http://dx.doi.org/10.1063/1.3569483 (6 pages) | Cited 7 times

Online Publication Date: 21 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The random phase approximation (RPA) stands on the top rung of the ladder of ground-state density functional approximations. The simple or direct RPA has been found to predict accurately many isoelectronic energy differences. A nonempirical local or semilocal correction to this direct RPA leaves isoelectronic energy differences almost unchanged, while improving total energies, ionization energies, etc., but fails to correct the RPA underestimation of molecular atomization energies. Direct RPA and its semilocal correction may miss part of the middle-range multicenter nonlocality of the correlation energy in a molecule. Here we propose a fully nonlocal, hybrid-functional-like addition to the semilocal correction. The added full nonlocality is important in molecules, but not in atoms. Under uniform-density scaling, this fully nonlocal correction scales like the second-order-exchange contribution to the correlation energy, an important part of the correction to direct RPA, and like the semilocal correction itself. For the atomization energies of ten molecules, and with the help of one fit parameter, it performs much better than the elaborate second-order screened exchange correction.
Show PACS
31.15.E- Density-functional theory

The two faces of static correlation

Joshua W. Hollett and Peter M. W. Gill

J. Chem. Phys. 134, 114111 (2011); http://dx.doi.org/10.1063/1.3570574 (5 pages) | Cited 7 times

Online Publication Date: 21 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Restricted Hartree–Fock (RHF) and UHF wavefunctions for beryllium-like ions with nuclear charge 3 ⩽ Z ⩽ 5 are found using a near-complete Slater basis set. The triplet (RHF → UHF) instability and correlation energy are investigated as a function of Z and we find that the instability vanishes for Z > 4.5. We reproduce this surprising behavior using a minimal-basis model and, by comparing with the stretched H2 molecule, conclude that “static” (also known as nondynamical, near-degeneracy, first-order, or strong) correlation comes in two flavors: one that can be captured by UHF and another that cannot. In the former (Type A), there is an “absolute near-degeneracy”; in the latter (Type B), there is a “relative near-degeneracy.” This dichotomy clarifies discussions of static correlation effects.
Show PACS
31.15.xr Self-consistent-field methods

Planar mixed flow and chaos: Lyapunov exponents and the conjugate-pairing rule

Stefano Bernardi, Federico Frascoli, Debra J. Searles, and B. D. Todd

J. Chem. Phys. 134, 114112 (2011); http://dx.doi.org/10.1063/1.3567095 (9 pages)

Online Publication Date: 21 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this work we characterize the chaotic properties of atomic fluids subjected to planar mixed flow, which is a linear combination of planar shear and elongational flows, in a constant temperature thermodynamic ensemble. With the use of a recently developed nonequilibrium molecular dynamics algorithm, compatible and reproducible periodic boundary conditions are realized so that Lyapunov spectra analysis can be carried out for the first time. Previous studies on planar shear and elongational flows have shown that Lyapunov spectra organize in different ways, depending on the character of the defining equations of the system. Interestingly, planar mixed flow gives rise to chaotic spectra that, on one hand, contain elements common to those of shear and elongational flows but also show peculiar, unique traits. In particular, the influence of the constituent flows in regards to the conjugate-pairing rule (CPR) is analyzed. CPR is observed in homogeneously thermostated systems whose adiabatic (or unthermostated) equations of motion are symplectic. We show that the component associated with the shear tends to selectively excite some of those degrees, and is responsible for violations in the rule.
Show PACS
47.52.+j Chaos in fluid dynamics
47.11.Mn Molecular dynamics methods
47.51.+a Mixing
back to top Gas Phase Dynamics and Structure: Spectroscopy, Molecular Interactions, Scattering, and Photochemistry

New ab initio potential energy surface for BrH2 and rate constants for the H + HBr → H2 + Br abstraction reaction

Bin Jiang, Changjian Xie, and Daiqian Xie

J. Chem. Phys. 134, 114301 (2011); http://dx.doi.org/10.1063/1.3563750 (9 pages) | Cited 4 times

Online Publication Date: 15 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A global potential energy surface (PES) for the electronic ground state of the BrH2 system was constructed based on the multireference configuration interaction (MRCI) method including the Davidson's correction using a large basis set. In addition, the spin–orbit correction were computed using the Breit–Pauli Hamiltonian and the unperturbed MRCI wavefunctions in the Br + H2 channel and the transition state region. Adding the correction to the ground state potential, the lowest spin–orbit correlated adiabatic potential was obtained. The characters of the new potential are discussed. Accurate initial state specified rate constants for the H + HBr → H2 + Br abstraction reaction were calculated using a time-dependent wave packet method. The predicted rate constants were found to be in excellent agreement with the available experimental values and much better than those obtained from a previous PES.
Show PACS
82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
82.20.Pm Rate constants, reaction cross sections, and activation energies
82.20.Kh Potential energy surfaces for chemical reactions
82.20.Db Transition state theory and statistical theories of rate constants

Unusual mechanism for H3+ formation from ethane as obtained by femtosecond laser pulse ionization and quantum chemical calculations

Peter M. Kraus, Martin C. Schwarzer, Nora Schirmel, Gunter Urbasch, Gernot Frenking, and Karl-Michael Weitzel

J. Chem. Phys. 134, 114302 (2011); http://dx.doi.org/10.1063/1.3561311 (6 pages) | Cited 1 time

Online Publication Date: 15 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The formation of H3+ from saturated hydrocarbon molecules represents a prototype of a complex chemical process, involving the breaking and the making of chemical bonds. We present a combined theoretical and experimental investigation providing for the first time an understanding of the mechanism of H3+ formation at the molecular level. The experimental approach involves femtosecond laser pulse ionization of ethane leading to H3+ ions with kinetic energies on the order of 4 to 6.5 eV. The theoretical approach involves high-level quantum chemical calculation of the complete reaction path. The calculations confirm that the process takes place on the potential energy surface of the ethane dication. A surprising result of the theoretical investigation is, that the transition state of the process can be formally regarded as a H2 molecule attached to a C2H42+ entity but IRC calculations show that it belongs to the reaction channel yielding C2H3+ + H3+. Experimentally measured kinetic energies of the correlated H3+ and C2H3+ ions confirm the reaction path suggested by theory.
Show PACS
82.50.Bc Processes caused by infrared radiation
82.20.Ej Quantum theory of reaction cross section
33.80.Wz Other multiphoton processes
33.80.Rv Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states)
82.20.Kh Potential energy surfaces for chemical reactions
33.80.Gj Diffuse spectra; predissociation, photodissociation

Relativistic multireference calculation of photodissociation of o-, m-, and p-bromofluorobenzene

Wen-Zuo Li, Shu-Feng Chen, and Ya-Jun Liu

J. Chem. Phys. 134, 114303 (2011); http://dx.doi.org/10.1063/1.3565445 (8 pages)

Online Publication Date: 15 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Quantum chemical calculations with relativistic effects were performed on the photodissociation of o-, m-, and p-bromofluorobenzene (o-, m-, and p-BrFPh) at 266 nm. The method of multistate second-order multiconfigurational perturbation theory in conjunction with spin–orbit interaction through complete active space state interaction was employed to calculate the potential energy curves for the ground and low-lying excited states of o-, m-, and p-BrFPh along their photodissociation reaction coordinates. The dissociation mechanisms with products of Br(2P3/2) and Br*(2P1/2) states were clarified with the computed potential energy curves and the surface crossings. The current calculations augmented previous theoretical investigations by including relativistic effects and resolved some differences of experimental assignment regarding the dissociation channels of o-, m-, and p-BrFPh.
Show PACS
31.30.J- Relativistic and quantum electrodynamic (QED) effects in atoms, molecules, and ions
33.80.Gj Diffuse spectra; predissociation, photodissociation
31.15.xp Perturbation theory
31.50.Bc Potential energy surfaces for ground electronic states
31.50.Df Potential energy surfaces for excited electronic states

Flickering dipoles in the gas phase: Structures, internal dynamics, and dipole moments of β-naphthol-H2O in its ground and excited electronic states

Adam J. Fleisher, Justin W. Young, David W. Pratt, Alessandro Cembran, and Jiali Gao

J. Chem. Phys. 134, 114304 (2011); http://dx.doi.org/10.1063/1.3562373 (12 pages) | Cited 2 times

Online Publication Date: 15 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Described here are the rotationally resolved S1–S0 electronic spectra of the acid–base complex cis-β-naphthol-H2O in the gas phase, both in the presence and absence of an applied electric field. The data show that the complex has a trans-linear O − H⋅⋅⋅O hydrogen bond configuration involving the −OH group of cis-β-naphthol and the oxygen lone pairs of the attached water molecule in both electronic states. The measured permanent electric dipole moments of the complex are 4.00 and 4.66 D in the S0 and S1 states, respectively. These reveal a small amount of photoinduced charge transfer between solute and solvent, as supported by density functional theory calculations and an energy decomposition analysis. The water molecule also was found to tunnel through a barrier to internal motion nearly equal in energy to kT at room temperature. The resulting large angular jumps in solvent orientation produce “flickering dipoles” that are recognized as being important to the dynamics of bulk water.
Show PACS
33.50.Dq Fluorescence and phosphorescence spectra
31.15.E- Density-functional theory
34.70.+e Charge transfer
33.15.Fm Bond strengths, dissociation energies
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility
31.30.jp Electron electric dipole moment

Perturbation theory treatment of pseudorotation in cyclic-N3

Dmitri Babikov

J. Chem. Phys. 134, 114305 (2011); http://dx.doi.org/10.1063/1.3563634 (7 pages) | Cited 3 times

Online Publication Date: 15 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A relatively simple treatment using perturbation theory is proposed to describe spectrum of pseudorotational states in cyclic-N3. The purpose is to develop an analytical expression that could be used to fit the experimentally determined spectrum of cyclic-N3, with purpose of identifying this molecule in the laboratory and deriving parameters of its potential energy surface directly from the experimental data. The perturbation theory expression derived in this work is used to fit the spectrum calculated numerically in the previous work [D. Babikov and B. Kendrick, J. Chem. Phys. 133, 174310 (2010)]. It is found that the second order of perturbation theory works well, giving a very good fit of the spectrum, with the rms deviation of only 0.26 cm−1. Analysis reveals that important characteristics of the potential energy surface, such as equilibrium geometry and pseudorotation barriers, are directly related to the features of spectrum, such as splittings, and can be readily derived from experimental data, when those become available.
Show PACS
33.20.Sn Rotational analysis
31.30.-i Corrections to electronic structure
82.20.Kh Potential energy surfaces for chemical reactions
31.15.xp Perturbation theory
31.50.-x Potential energy surfaces
FREE

Rotationally correlated reactivity in the CH (v = 0, J, Fi) + O2 → OH (A) + CO reaction

H. Ohoyama, K. Yamakawa, R. Oda, Y. Nagamachi, and T. Kasai

J. Chem. Phys. 134, 114306 (2011); http://dx.doi.org/10.1063/1.3560660 (10 pages)

Online Publication Date: 16 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The rotational-state-selected CH (v = 0, J, Fi) beam has been prepared by using an electric hexapole and applied to the crossed beam reaction of CH (v = 0, J, Fi) + O2 → OH (A) + CO at different O2 beam conditions. The rotational state selected reactive cross sections of CH (RSSRCS-CH) turn out to depend remarkably on the rotational state distribution of O2 molecules at a collision energy of ∼ 0.19 eV. The reactivity of CH molecules in the N = 1 rotational states (namely |J = 1/2, F2〉 and |J = 3/2, F1〉 states, N designates the angular momentum excluding spin) becomes strongly enhanced upon a lowering of the rotational temperature of the O2 beam. The RSSRCS-CH in these two rotational states correlate linearly with the population of O2 molecule in the specific KO2 frame rotation number states: CH (|J = 1/2,F2〉) with O2(|KO2 = 1〉); CH (|J = 3/2,F1〉) with O2(|KO2 = 3〉).These linear correlations mean that the rotational-state-selected CH molecules are selectively reactive upon the incoming O2 molecules in a specific rotational state; here, we use the term “rotationally correlated reactivity” to such specific reactivity depending on the combination of the rotational states between two molecular reactants. In addition, the steric asymmetry in the oriented CH (|J = 1/2, F2, M = 1/2〉) + O2 (|KO2 = 1〉) reaction turns out to be negligible (< ±1%). This observation supports the reaction mechanism as theoretically predicted by Huang et al. [J. Phys. Chem. A 106, 5490 (2002)] that the first step is an intermediate formation with no energy barrier in which C-atom of CH molecule attacks on one O-atom of O2 molecule at a sideways configuration.
Show PACS
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
82.20.Bc State selected dynamics and product distribution
82.20.Rp State to state energy transfer

Low-lying excited states and nonradiative processes of the adenine analogues 7H- and 9H-2-aminopurine

Simon Lobsiger, Rajeev K. Sinha, Maria Trachsel, and Samuel Leutwyler

J. Chem. Phys. 134, 114307 (2011); http://dx.doi.org/10.1063/1.3567090 (14 pages)

Online Publication Date: 16 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have investigated the UV vibronic spectra and excited-state nonradiative processes of the 7H- and 9H-tautomers of jet-cooled 2-aminopurine (2AP) and of the 9H-2AP-d4 and -d5 isotopomers, using two-color resonant two-photon ionization spectroscopy at 0.3 and 0.045 cm−1 resolution. The S1 ← S0 transition of 7H-2AP was observed for the first time. It lies ∼ 1600 cm−1 below that of 9H-2AP, is ∼1000 times weaker and exhibits only in-plane vibronic excitations. In contrast, the S1 ← S0 spectra of 9H-2AP, 9H-2AP-d4, and 9H-2AP-d5 show numerous low-frequency bands that can be systematically assigned to overtone and combinations of the out-of-plane vibrations ν1′, ν2′, and ν3′. The intensity of these out-of-plane bands reflects an out-of-plane deformation in the 1ππ*(La) state. Approximate second-order coupled-cluster theory also predicts that 2-aminopurine undergoes a “butterfly” deformation in its lowest 1ππ* state. The rotational contours of the 9H-2AP, 9H-2AP-d4, and 9H-2AP-d5 000 bands and of eight vibronic bands of 9H-2AP up to 000+600 cm−1 exhibit 75%–80% in-plane (a/b) polarization, which is characteristic for a 1ππ* excitation. A 20%–25% c-axis (perpendicular) transition dipole moment component may indicate coupling of the 1ππ* bright state to the close-lying 1nπ* dark state. However, no 1nπ* vibronic bands were detected below or up to 500 cm−1 above the 1ππ* 000 band. Following 1ππ* excitation, 9H-2AP undergoes a rapid nonradiative transition to a lower-lying long-lived state with a lifetime ⩾5μs. The ionization potential of 9H-2AP was measured via the 1ππ* state (IP = 8.020 eV) and the long-lived state (IP > 9.10 eV). The difference shows that the long-lived state lies ⩾1.08 eV below the 1ππ* state. Time-dependent B3LYP calculations predict the 3ππ* (T1) state 1.12 eV below the 1ππ* state, but place the 1nπ* (S1) state close to the 1ππ* state, implying that the long-lived state is the lowest triplet (T1) and not the 1nπ* state.
Show PACS
33.50.-j Fluorescence and phosphorescence; radiationless transitions, quenching (intersystem crossing, internal conversion)
33.20.Wr Vibronic, rovibronic, and rotation-electron-spin interactions
31.15.bw Coupled-cluster theory
31.50.Df Potential energy surfaces for excited electronic states
33.80.-b Photon interactions with molecules
33.20.Lg Ultraviolet spectra

Sequential bond energies and barrier heights for the water loss and charge separation dissociation pathways of Cd2+(H2O)n, n = 3–11

Theresa E. Cooper and P. B. Armentrout

J. Chem. Phys. 134, 114308 (2011); http://dx.doi.org/10.1063/1.3553813 (18 pages)

Online Publication Date: 17 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The bond dissociation energies for losing one water from Cd2+(H2O)n complexes, n = 3–11, are measured using threshold collision-induced dissociation in a guided ion beam tandem mass spectrometer coupled with a thermal electrospray ionization source. Kinetic energy dependent cross sections are obtained for n = 4–11 complexes and analyzed to yield 0 K threshold measurements for loss of one, two, and three water ligands after accounting for multiple collisions, kinetic shifts, and energy distributions. The threshold measurements are converted from 0 to 298 K values to give the hydration enthalpies and free energies for sequentially losing one water from each complex. Theoretical geometry optimizations and single point energy calculations are performed on reactant and product complexes using several levels of theory and basis sets to obtain thermochemistry for comparison to experiment. The charge separation process, Cd2+(H2O)n → CdOH+(H2O)m + H+(H2O)n−m−1, is also observed for n = 4 and 5 and the competition between this process and water loss is analyzed. Rate-limiting transition states for the charge separation process at n = 3–6 are calculated and compared to experimental threshold measurements resulting in the conclusion that the critical size for this dissociation pathway of hydrated cadmium is ncrit = 4.
Show PACS
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
33.15.Ry Ionization potentials, electron affinities, molecular core binding energy
82.60.Cx Enthalpies of combustion, reaction, and formation
82.60.Lf Thermodynamics of solutions
33.15.Fm Bond strengths, dissociation energies

[1 + 1] photodissociation of CS2+(math2Πg) via the vibrationally mediated math2Σu+ state: Multichannels exhibiting and mode specific dynamics

Jialin Li, Cuimei Zhang, Qun Zhang, Yang Chen, Cunshun Huang, and Xueming Yang

J. Chem. Phys. 134, 114309 (2011); http://dx.doi.org/10.1063/1.3567071 (7 pages) | Cited 4 times

Online Publication Date: 17 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Dissociation dynamics of CS 2+ vibrationally mediated via its math2Σu+ state, was studied using the time-sliced velocity map imaging technique. The parent CS 2+ cation was prepared in its math2Πg ground state through a [3 + 1] resonance enhanced multiphoton ionization process, via the 4pσ3Πu intermediate Rydberg state of neutral CS2 molecule at 483.14 nm. CS 2+(math2Πg) was dissociated by a [1 + 1] photoexcitation mediated via the vibrationally selected math state over a wavelength range of 267–283 nm. At these wavelengths the math2Σg+ and math2Σu+ states are excited, followed by numerous S+ and CS+ dissociation channels. The S+ channels specified as three distinct regions were shown with vibrationally resolved structures, in contrast to the less-resolved structures being presented in the CS+ channels. The average translational energy releases were obtained, and the S+/CS+ branching ratios with mode specificity were measured. Two types of dissociation mechanisms are proposed. One mechanism is the direct coupling of the math and math states with the repulsive satellite states leading to the fast photofragmentation. The other mechanism is the internal conversion of the math and math states to the math state, followed by the slow fragmentation occurred via the coupling with the repulsive satellite states.
Show PACS
33.80.Gj Diffuse spectra; predissociation, photodissociation
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.80.Eh Autoionization, photoionization, and photodetachment
33.80.Rv Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states)
33.50.Hv Radiationless transitions, quenching

The effect of rotational and translational energy exchange on tracer diffusion in rough hard sphere fluids

Olga Kravchenko and Mark Thachuk

J. Chem. Phys. 134, 114310 (2011); http://dx.doi.org/10.1063/1.3562369 (11 pages) | Cited 3 times

Online Publication Date: 17 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A study is presented of tracer diffusion in a rough hard sphere fluid. Unlike smooth hard spheres, collisions between rough hard spheres can exchange rotational and translational energy and momentum. It is expected that as tracer particles become larger, their diffusion constants will tend toward the Stokes–Einstein hydrodynamic result. It has already been shown that in this limit, smooth hard spheres adopt “slip” boundary conditions. The current results show that rough hard spheres adopt boundary conditions proportional to the degree of translational–rotational energy exchange. Spheres for which this exchange is the largest adopt “stick” boundary conditions while those with more intermediate exchange adopt values between the “slip” and “stick” limits. This dependence is found to be almost linear. As well, changes in the diffusion constants as a function of this exchange are examined and it is found that the dependence is stronger than that suggested by the low-density, Boltzmann result. Compared with smooth hard spheres, real molecules undergo inelastic collisions and have attractive wells. Rough hard spheres model the effect of inelasticity and show that even without the presence of attractive forces, the boundary conditions for large particles can deviate from “slip” and approach “stick.”
Show PACS
66.10.C- Diffusion and thermal diffusion
82.80.-d Chemical analysis and related physical methods of analysis
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.dq Other elastic constants

Quantum vibrational analysis and infrared spectra of microhydrated sodium ions using an ab initio potential

Eugene Kamarchik, Yimin Wang, and Joel M. Bowman

J. Chem. Phys. 134, 114311 (2011); http://dx.doi.org/10.1063/1.3567186 (9 pages)

Online Publication Date: 18 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We present a full-dimensional potential energy surface and a dipole moment surface (DMS) for hydrated sodium ion. These surfaces are based on an n-body expansion for both the potential energy and the dipole moment, truncated at the two-body level for the H2O–Na+ interaction and also for the DMS. The water–water interaction is truncated at the three-body level. The new full-dimensional two-body H2O–Na+ potential is a fit to roughly 20 000 coupled-cluster single double (triple)/aug-cc-pVTZ energies. Properties of this two-body potential and the potential describing (H2O)nNa+ clusters, with n up to 4 are given. We then report anharmonic, coupled vibrational calculations with the “local-monomer model” to obtain infrared spectra and also 0 K radial distribution functions for these clusters. Some comparisons are made with the recent infrared predissociation spectroscopy experiments of Miller and Lisy [J. Am. Chem. Soc. 130, 15381 (2008).]
Show PACS
33.20.Tp Vibrational analysis
33.20.Ea Infrared spectra
31.50.-x Potential energy surfaces
82.30.Fi Ion-molecule, ion-ion, and charge-transfer reactions
31.15.bw Coupled-cluster theory
33.80.Gj Diffuse spectra; predissociation, photodissociation

Time-resolved study of excited states of N2 near its first ionization threshold

Angelica Moise, Kevin C. Prince, and Robert Richter

J. Chem. Phys. 134, 114312 (2011); http://dx.doi.org/10.1063/1.3560909 (9 pages) | Cited 1 time

Online Publication Date: 18 March 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Two-photon, two-color double-resonance ionization spectroscopy combining synchrotron vacuum ultraviolet radiation with a tunable near-infrared (NIR) laser has been used to investigate gerade symmetry states of the nitrogen molecule. The rotationally resolved spectrum of an autoionizing 1Σg− state has been excited via the intermediate c4 (v = 0) 1Πu Rydberg state. We present the analysis of the band located at Tv = 10 800.7 ± 2 cm−1 with respect to the intermediate state, 126 366 ± 11 cm−1 with respect to the ground state, approximately 700 cm−1 above the first ionization threshold. From the analysis a rotational constant of Bv = 1.700 ± 0.005 cm−1 has been determined for this band. Making use of the pulsed structure of the two radiation beams, lifetimes of several rotational levels of the intermediate state have been measured. We also report rotationally-averaged fluorescence lifetimes (300 K) of several excited electronic states accessible from the ground state by absorption of one photon in the range of 13.85–14.9 eV. The averaged lifetimes of the c4 (0) and c5 (0) states are 5.6 and 4.4 ns, respectively, while the b′ (12), c′4 (4, 5, 6), and c′5 (0) states all have lifetimes in the range of hundreds of picoseconds.
Show PACS
33.80.Eh Autoionization, photoionization, and photodetachment
33.70.Ca Oscillator and band strengths, lifetimes, transition moments, and Franck-Condon factors
33.50.Dq Fluorescence and phosphorescence spectra
33.80.Rv Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states)
FREE

A quantum defect model for the s, p, d, and f Rydberg series of CaF

Jeffrey J. Kay, Stephen L. Coy, Bryan M. Wong, Christian Jungen, and Robert W. Field

J. Chem. Phys. 134, 114313 (2011); http://dx.doi.org/10.1063/1.3565967 (21 pages) | Cited 3 times

Online Publication Date: 18 March 2011

Full Text: Read Online (HTML) | Download PDF


See Also: Erratum

Show Abstract
We present an improved quantum defect theory model for the “s,” “p,” “d,” and “f” Rydberg series of CaF. The model, which is the result of an exhaustive fit of high-resolution spectroscopic data, parameterizes the electronic structure of the ten (“s”Σ, “p”Σ, “p”Π, “d”Σ, “d”Π, “d”Δ, “f”Σ, “f”Π, “f”Δ, and “f”Φ) Rydberg series of CaF in terms of a set of twenty μℓℓ′(Λ) quantum defect matrix elements and their dependence on both internuclear separation and on the binding energy of the outer electron. Over 1000 rovibronic Rydberg levels belonging to 131 observed electronic states of CaF with n* ≥ 5 are included in the fit. The correctness and physical validity of the fit model are assured both by our intuition-guided combinatorial fit strategy and by comparison with R-matrix calculations based on a one-electron effective potential. The power of this quantum defect model lies in its ability to account for the rovibronic energy level structure and nearly all dynamical processes, including structure and dynamics outside of the range of the current observations. Its completeness places CaF at a level of spectroscopic characterization similar to NO and H2.
Show PACS
33.15.Ry Ionization potentials, electron affinities, molecular core binding energy
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.20.Vq Vibration-rotation analysis
33.15.Bh General molecular conformation and symmetry; stereochemistry
Page 1 of 3 Pages Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Your Recent History Recent History Help

Recently Viewed

  1. Re-entrant phase behavior for systems with competition between phase separation and self-assembly
  2. Chemical response of aldehydes to compression between (0001) surfaces of α-alumina
  3. The decay mechanism of photoexcited guanine − A nonadiabatic dynamics study
  4. A first principles based polarizable O(N) interatomic force field for bulk silica
  5. The role of stochasticity on compactness of the native state of protein peptide backbone
Go to AIP Home
Copyright © American Institute of Physics
close