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

You Tube Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

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

14 Jan 2013

Volume 138, Issue 2, Articles (02xxxx)

Issue Cover Spotlight Figure

J. Chem. Phys. 138, 020901 (2013); http://dx.doi.org/10.1063/1.4773981 (10 pages)

Raymond Kapral
Enlarge Image | Read More
Page 1 of 3 Pages Next Page | Jump to Page
back to top
RSS Feeds
FREE

Perspective: Nanomotors without moving parts that propel themselves in solution

Raymond Kapral

J. Chem. Phys. 138, 020901 (2013); http://dx.doi.org/10.1063/1.4773981 (10 pages)

Online Publication Date: 8 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Self-propelled nanomotors use chemical energy to produce directed motion. Like many molecular motors they suffer strong perturbations from the environment in which they move as a result of thermal fluctuations and do not rely on inertia for their propulsion. Such tiny motors are the subject of considerable research because of their potential applications, and a variety of synthetic motors have been made and are being studied for this purpose. Chemically powered self-propelled nanomotors without moving parts that rely on asymmetric chemical reactions to effect directed motion are the focus of this article. The mechanisms they use for propulsion, how size and fuel sources influence their motion, how they cope with strong molecular fluctuations, and how they behave collectively are described. The practical applications of such nanomotors are largely unrealized and the subject of speculation. Since molecular motors are ubiquitous in biology and perform a myriad of complex tasks, the hope is that synthetic motors might be able to perform analogous tasks. They may have the potential to change our perspective on how chemical dynamics takes place in complex systems.
Show PACS
87.85.Rs Nanotechnologies-applications
82.39.Rt Reactions in complex biological systems
87.15.Ya Fluctuations
87.19.Pp Biothermics and thermal processes in biology
87.15.hj Transport dynamics
back to top
RSS Feeds
FREE

Communication: How to generate and measure anomalous diffusion in simple systems

A. Fuliński

J. Chem. Phys. 138, 021101 (2013); http://dx.doi.org/10.1063/1.4775737 (4 pages)

Online Publication Date: 10 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
It is shown that in systems with time-dependent and/or spatially nonuniform temperature T(t, r), the diffusion (Brownian motion) is anomalous (AD). A few examples of simple arrangements, easy for experimental realization, are discussed in detail. Proposed measurements will enable also the observation of transitions from normal to anomalous diffusion. New effects are predicted: (i) zero-mean oscillations of T(t) accelerate AD (pumping effect), (ii) the combination of temporal and spatial variations of temperature may lead to superballistic AD, (iii) various forms of T(t, r) may result in non-algebraic AD including exponential diffusion. One can expect similar effects in inflationary systems with time-dependent metric and in expanding/contracting gases.
Show PACS
05.60.-k Transport processes
05.40.Jc Brownian motion
FREE

Communication: A simple analytical formula for the free energy of ligand–receptor-mediated interactions

Stefano Angioletti-Uberti, Patrick Varilly, Bortolo M. Mognetti, Alexei V. Tkachenko, and Daan Frenkel

J. Chem. Phys. 138, 021102 (2013); http://dx.doi.org/10.1063/1.4775806 (4 pages) | Cited 1 time

Online Publication Date: 10 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Recently [P. Varilly, S. Angioletti-Uberti, B. M. Mognetti, and D. Frenkel, “A general theory of DNA-mediated and other valence-limited colloidal interactions,” J. Chem. Phys. 137, 094108 (2012)10.1063/1.4748100], we presented a general theory for calculating the strength and properties of colloidal interactions mediated by ligand–receptor bonds (such as those that bind DNA-coated colloids). In this Communication, we derive a surprisingly simple analytical form for the interaction free energy, which was previously obtainable only via a costly numerical thermodynamic integration. As a result, the computational effort to obtain potentials of interaction is significantly reduced. Moreover, we can gain insight from this analytic expression for the free energy in limiting cases. In particular, the connection of our general theory to other previous specialised approaches is now made transparent. This important simplification will significantly broaden the scope of our theory.
Show PACS
82.39.Pj Nucleic acids, DNA and RNA bases
82.70.Dd Colloids
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
FREE

Communication: Paramagnetic NMR chemical shift in a spin state subject to zero-field splitting

Alessandro Soncini and Willem Van den Heuvel

J. Chem. Phys. 138, 021103 (2013); http://dx.doi.org/10.1063/1.4775809 (3 pages) | Cited 1 time

Online Publication Date: 10 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We derive a general formula for the paramagnetic NMR nuclear shielding tensor of an open-shell molecule in a pure spin state, subject to a zero-field splitting (ZFS). Our findings are in contradiction with a previous proposal. We present a simple application of the newly derived formula to the case of a triplet ground state split by an easy-plane ZFS spin Hamiltonian. When kT is much smaller than the ZFS gap, thus a single non-degenerate level is thermally populated, our approach correctly predicts a temperature-independent paramagnetic shift, while the previous theory leads to a Curie temperature dependence.
Show PACS
33.25.+k Nuclear resonance and relaxation
FREE

Communication: One third: A new recipe for the PBE0 paradigm

Ciro A. Guido, Eric Brémond, Carlo Adamo, and Pietro Cortona

J. Chem. Phys. 138, 021104 (2013); http://dx.doi.org/10.1063/1.4775591 (4 pages) | Cited 1 time

Online Publication Date: 11 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We analyze the performances of the parameter-free hybrid density functional PBE0-1/3 obtained combining the PBE generalized-gradient functional with a predefined amount of exact exchange of 1/3, as recently discussed by Cortona [J. Chem. Phys. 136, 086101 (2012)10.1063/1.3690462]. The numerical results that we have obtained for various properties, such as atomization energies (G2-148 dataset), weak interactions (NCB31 dataset), hydrogen-bond length optimizations, and dissociation energies (HB10 dataset), and vertical excitation energies, show an increased performance of PBE0-1/3 with respect to the widely used PBE0. We therefore propose to use one third as the mixing coefficient for the PBE-based hybrid functional.
Show PACS
31.15.E- Density-functional theory
31.30.jh QED corrections to long-range and weak interactions
33.15.Fm Bond strengths, dissociation energies
FREE

Communication: Theoretical prediction of the structure and spectroscopic properties of the math and math states of hydroxymethyl peroxy (HOCH2OO) radical

Mickael G. Delcey, Roland Lindh, Roberto Linguerri, Majdi Hochlaf, and Joseph S. Francisco

J. Chem. Phys. 138, 021105 (2013); http://dx.doi.org/10.1063/1.4775782 (4 pages)

Online Publication Date: 11 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The hydroxymethyl peroxy (HMOO) radical is a radical product from the oxidation of non-methane hydrocarbons. The present study provides theoretical prediction of critical spectroscopic features of this radical that should aid in its experimental characterization. Structure, rotational constants, and harmonic frequencies are presented for the ground and first excited electronic states of HMOO. The adiabatic transition energy for the math←math process is 7360 cm−1, suggesting that this transition, occurring in the mid to near infrared, is the most promising candidate for observing the radical spectroscopically. The band origin of the math←math transition of HMOO is calibrated and benchmarked with the corresponding state of the HOO radical, which is experimentally and theoretically well characterized.
Show PACS
33.15.Bh General molecular conformation and symmetry; stereochemistry
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.20.Ea Infrared spectra
33.20.Sn Rotational analysis
back to top
RSS Feeds
back to top Theoretical Methods and Algorithms

Analytical second derivatives of excited-state energy within the time-dependent density functional theory coupled with a conductor-like polarizable continuum model

Jie Liu and WanZhen Liang

J. Chem. Phys. 138, 024101 (2013); http://dx.doi.org/10.1063/1.4773397 (10 pages)

Online Publication Date: 8 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This work extends our previous works [J. Liu and W. Z. Liang, J. Chem. Phys. 135, 014113 (2011)10.1063/1.3605504; J. Liu and W. Z. Liang, J. Chem. Phys. 135, 184111 (2011)]10.1063/1.3659312 on analytical excited-state Hessian within the framework of time-dependent density functional theory (TDDFT) to couple with a conductor-like polarizable continuum model (CPCM). The formalism, implementation, and application of analytical first and second energy derivatives of TDDFT/CPCM excited state with respect to the nuclear and electric perturbations are presented. Their performances are demonstrated by the calculations of excitation energies, excited-state geometries, and harmonic vibrational frequencies for a number of benchmark systems. The calculated results are in good agreement with the corresponding experimental data or other theoretical calculations, indicating the reliability of the current computer implementation of the developed algorithms. Then we made some preliminary applications to calculate the resonant Raman spectrum of 4-hydroxybenzylidene-2,3-dimethyl-imidazolinone in ethanol solution and the infrared spectra of ground and excited states of 9-fluorenone in methanol solution.
Show PACS
31.15.vj Electron correlation calculations for atoms and ions: excited states
31.15.xp Perturbation theory
33.20.Tp Vibrational analysis
31.15.am Relativistic configuration interaction (CI) and many-body perturbation calculations
31.15.ee Time-dependent density functional theory

On the physical role of exchange in the formation of an intramolecular bond path between two electronegative atoms

Vincent Tognetti and Laurent Joubert

J. Chem. Phys. 138, 024102 (2013); http://dx.doi.org/10.1063/1.4770495 (8 pages)

Online Publication Date: 8 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this paper, we present a detailed energetic decomposition of intramolecular O⋯X interactions (X being O, S, or a halogen atom) based on the interacting quantum atoms approach of Pendás and co-workers. The nature of these interactions (repulsive or attractive, more or less electrostatic) is discussed in the framework of Bader's atoms in molecules theory, a particular emphasis being put on delocalization (measured by delocalization indexes and in terms of the source function) and on the exchange contributions. Notably, the concept of exchange channels introduced by Pendás and collaborators provides means of rationalizing and predicting the presence of bond critical points, enhancing the physical meaning of bond paths.
Show PACS
31.15.eg Exchange-correlation functionals (in current density functional theory)
33.15.Fm Bond strengths, dissociation energies
34.20.Cf Interatomic potentials and forces

H2O photodissociation in the first absorption band: Entangled trajectory molecular dynamics method

Feng Xu (徐峰), Lifei Wang (王立飞), Craig C. Martens, and Yujun Zheng (郑雨军)

J. Chem. Phys. 138, 024103 (2013); http://dx.doi.org/10.1063/1.4774023 (7 pages) | Cited 1 time

Online Publication Date: 9 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We investigate H2O photodissociation in its first absorption band using entangled trajectory molecular dynamics method. We compare our results of entangled trajectories with exact quantum mechanical calculations, the overall agreement with the exact results is reasonable. To help understanding we show the photodissociation process with our entangled trajectories and the effect of the entangled trajectories in the system.
Show PACS
33.80.Gj Diffuse spectra; predissociation, photodissociation
42.50.Dv Quantum state engineering and measurements
31.15.xv Molecular dynamics and other numerical methods
Author Select

Implementation of quantum logic gates using polar molecules in pendular states

Jing Zhu, Sabre Kais, Qi Wei, Dudley Herschbach, and Bretislav Friedrich

J. Chem. Phys. 138, 024104 (2013); http://dx.doi.org/10.1063/1.4774058 (7 pages) | Cited 1 time

Online Publication Date: 10 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We present a systematic approach to implementation of basic quantum logic gates operating on polar molecules in pendular states as qubits for a quantum computer. A static electric field prevents quenching of the dipole moments by rotation, thereby creating the pendular states; also, the field gradient enables distinguishing among qubit sites. Multi-target optimal control theory is used as a means of optimizing the initial-to-target transition probability via a laser field. We give detailed calculations for the SrO molecule, a favorite candidate for proposed quantum computers. Our simulation results indicate that NOT, Hadamard and CNOT gates can be realized with high fidelity, as high as 0.985, for such pendular qubit states.
Show PACS
03.67.Lx Quantum computation architectures and implementations
03.67.Mn Entanglement measures, witnesses, and other characterizations
03.65.Ta Foundations of quantum mechanics; measurement theory

Gaussian basis sets for highly excited and resonance states of helium

Petra Ruth Kaprálová-Žďánská and Jan Šmydke

J. Chem. Phys. 138, 024105 (2013); http://dx.doi.org/10.1063/1.4772468 (17 pages)

Online Publication Date: 10 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A consistent method for optimizing Gaussian primitives for Rydberg and multiply excited helium states is designed. A novel series for the “exponentially tempered Gaussians” is introduced, which is markedly more efficient than the commonly used series of even tempered Gaussians. The optimization is made computationally feasible due to an approximate calculation of excited states using the effective one-electron Hamiltonian that is defined as Fockian from which the redundant Coulomb and exchange terms are dropped. Finally, ExTG5G and ExTG7F Gaussian basis sets are proposed. They enable calculations of the helium spectrum all the way from the ground state up to the (5, 4)5 1Se and (6, 5)7 1Se doubly excited resonances, respectively, mostly in the spectroscopic accuracy of 1 cm−1.
Show PACS
31.15.bw Coupled-cluster theory

Correlated driving and dissipation in two-dimensional spectroscopy

Jian Xu, Hou-Dao Zhang, Rui-Xue Xu, and YiJing Yan

J. Chem. Phys. 138, 024106 (2013); http://dx.doi.org/10.1063/1.4773472 (14 pages)

Online Publication Date: 10 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The correlation between coherent driving and non-Markovian dissipation plays a vital role in optical processes. To exhibit its effect on the simulation of optical spectroscopy, we explore the correlated driving-dissipation equation (CODDE) [R. X. Xu and Y. J. Yan, J. Chem. Phys. 116, 9196 (2002)]10.1063/1.1474579, which modifies the conventional Redfield theory with the inclusion of correlated driving-dissipation effect at the second-order system–bath coupling level. With an exciton model mimicking the Fenna–Matthews–Olson pigment-protein complex, we compare between the Redfield theory, CODDE, and exact hierarchical dynamics, for their results on linear absorption and coherent two-dimensional spectroscopy. We clarify that the failure of Redfield approach originates mainly from the neglect of driving–dissipation correlation, rather than its second-order nature. We further propose a dynamical inhomogeneity parameter to quantify the applicable range of CODDE. Our results indicate that CODDE is an efficient and quantifiable theory for many light-harvesting complexes of interest. To facilitate the evaluation of multi-dimensional spectroscopy, we also develop the mixed Heisenberg–Schrödinger picture scheme that is valid for any dynamics implementation on nonlinear response functions.
Show PACS
42.50.Nn Quantum optical phenomena in absorbing, amplifying, dispersive and conducting media; cooperative phenomena in quantum optical systems
42.50.Ar Photon statistics and coherence theory

Density cumulant functional theory: The DC-12 method, an improved description of the one-particle density matrix

Alexander Yu. Sokolov, Andrew C. Simmonett, and Henry F. Schaefer, III

J. Chem. Phys. 138, 024107 (2013); http://dx.doi.org/10.1063/1.4773580 (9 pages)

Online Publication Date: 10 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Density cumulant functional theory (DCFT) is a theory that, in principle, can compute energies and properties exactly without a wavefunction. To accomplish this, the energy is expressed as an exact, known functional of the one-particle density matrix and two-particle density cumulant. The correlation contribution to the one-particle density matrix is obtained from the cumulant, to eliminate redundancy in the equations. The previous formulation of DCFT introduced this relationship in an approximate way, to obtain tractable equations. In this research, it is demonstrated that the correlation contribution to the one-particle density matrix can be extracted exactly from the cumulant, with minimal computational overhead and no increase in the asymptotic cost of the theory. We present numerical results, showing the improvements resulting from this reformulation (DC-12), and offer a perturbative analysis of the new equations to compare them to their predecessors.
Show PACS
31.15.E- Density-functional theory

Non-Hermitian wave packet approximation of Bloch optical equations

Eric Charron and Maxim Sukharev

J. Chem. Phys. 138, 024108 (2013); http://dx.doi.org/10.1063/1.4774056 (10 pages)

Online Publication Date: 11 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We introduce a non-Hermitian approximation of Bloch optical equations. This approximation provides a complete description of the excitation, relaxation, and decoherence dynamics of ensembles of coupled quantum systems in weak laser fields, taking into account collective effects and dephasing. In the proposed method, one propagates the wave function of the system instead of a complete density matrix. Relaxation and dephasing are taken into account via automatically adjusted time-dependent gain and decay rates. As an application, we compute the numerical wave packet solution of a time-dependent non-Hermitian Schrödinger equation describing the interaction of electromagnetic radiation with a quantum nano-structure, and compare the calculated transmission, reflection, and absorption spectra with those obtained from the numerical solution of the Liouville-von Neumann equation. It is shown that the proposed wave packet scheme is significantly faster than the propagation of the full density matrix while maintaining small error. We provide the key ingredients for easy-to-use implementation of the proposed scheme and identify the limits and error scaling of this approximation.
Show PACS
42.50.-p Quantum optics
03.65.Ge Solutions of wave equations: bound states
03.65.Yz Decoherence; open systems; quantum statistical methods

Directed motion of periodically driven molecular motors: A graph-theoretical approach

Alexey V. Akimov, Dibyendu Mandal, Vladimir Y. Chernyak, and Nikolai A. Sinitsyn

J. Chem. Phys. 138, 024109 (2013); http://dx.doi.org/10.1063/1.4774270 (12 pages)

Online Publication Date: 11 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We propose a numerical algorithm for calculation of quantized directed motion of a stochastic system of interacting particles induced by periodic changes of control parameters on the graph of microstates. As a main application, we consider models of catenane molecular motors, which demonstrated the possibility of a similar control of directed motion of molecular components. We show that our algorithm allows one to calculate the motion of a system in the space of its microstates even when the considered phase space is combinatorially large (∼1 × 106 microscopic states). Several general observations are made about the structure of the phase diagram of the systems studied, which may be used for rational design and efficient control of new generations of molecular motors.
Show PACS
85.65.+h Molecular electronic devices

The effect of quantization on the full configuration interaction quantum Monte Carlo sign problem

M. H. Kolodrubetz, J. S. Spencer, B. K. Clark, and W. M.C. Foulkes

J. Chem. Phys. 138, 024110 (2013); http://dx.doi.org/10.1063/1.4773819 (7 pages)

Online Publication Date: 11 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The sign problem in full configuration interaction quantum Monte Carlo (FCIQMC) without annihilation can be understood as an instability of the psi-particle population to the ground state of the matrix obtained by making all off-diagonal elements of the Hamiltonian negative. Such a matrix, and hence the sign problem, is basis dependent. In this paper, we discuss the properties of a physically important basis choice: first versus second quantization. For a given choice of single-particle orbitals, we identify the conditions under which the fermion sign problem in the second quantized basis of antisymmetric Slater determinants is identical to the sign problem in the first quantized basis of unsymmetrized Hartree products. We also show that, when the two differ, the fermion sign problem is always less severe in the second quantized basis. This supports the idea that FCIQMC, even in the absence of annihilation, improves the sign problem relative to first quantized methods. Finally, we point out some theoretically interesting classes of Hamiltonians where first and second quantized sign problems differ, and others where they do not.
Show PACS
31.15.V- Electron correlation calculations for atoms, ions and molecules
31.15.xv Molecular dynamics and other numerical methods

Benchmarking density-functional theory calculations of NMR shielding constants and spin–rotation constants using accurate coupled-cluster calculations

Andrew M. Teale, Ola B. Lutnæs, Trygve Helgaker, David J. Tozer, and Jürgen Gauss

J. Chem. Phys. 138, 024111 (2013); http://dx.doi.org/10.1063/1.4773016 (21 pages) | Cited 2 times

Online Publication Date: 11 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Accurate sets of benchmark nuclear-magnetic-resonance shielding constants and spin–rotation constants are calculated using coupled-cluster singles–doubles (CCSD) theory and coupled-cluster singles–doubles–perturbative-triples [CCSD(T)] theory, in a variety of basis sets consisting of (rotational) London atomic orbitals. The accuracy of the calculated coupled-cluster constants is established by a careful comparison with experimental data, taking into account zero-point vibrational corrections. Coupled-cluster basis-set convergence is analyzed and extrapolation techniques are employed to estimate basis-set-limit quantities, thereby establishing an accurate benchmark data set. Together with the set provided for rotational g-tensors and magnetizabilities in our previous work [O. B. Lutnæs, A. M. Teale, T. Helgaker, D. J. Tozer, K. Ruud, and J. Gauss, J. Chem. Phys. 131, 144104 (2009)]10.1063/1.3242081, it provides a substantial source of consistently calculated high-accuracy data on second-order magnetic response properties. The utility of this benchmark data set is demonstrated by examining a wide variety of Kohn–Sham exchange–correlation functionals for the calculation of these properties. None of the existing approximate functionals provide an accuracy competitive with that provided by CCSD or CCSD(T) theory. The need for a careful consideration of vibrational effects is clearly illustrated. Finally, the pure coupled-cluster results are compared with the results of Kohn–Sham calculations constrained to give the same electronic density. Routes to future improvements are discussed in light of this comparison.
Show PACS
31.15.eg Exchange-correlation functionals (in current density functional theory)
31.15.xp Perturbation theory
33.20.Sn Rotational analysis
33.20.Wr Vibronic, rovibronic, and rotation-electron-spin interactions
33.25.+k Nuclear resonance and relaxation
31.15.bw Coupled-cluster theory

Fast-SAXS-pro: A unified approach to computing SAXS profiles of DNA, RNA, protein, and their complexes

Krishnakumar M. Ravikumar, Wei Huang, and Sichun Yang

J. Chem. Phys. 138, 024112 (2013); http://dx.doi.org/10.1063/1.4774148 (7 pages)

Online Publication Date: 11 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A generalized method, termed Fast-SAXS-pro, for computing small angle x-ray scattering (SAXS) profiles of proteins, nucleic acids, and their complexes is presented. First, effective coarse-grained structure factors of DNA nucleotides are derived using a simplified two-particle-per-nucleotide representation. Second, SAXS data of a 18-bp double-stranded DNA are measured and used for the calibration of the scattering contribution from excess electron density in the DNA solvation layer. Additional test on a 25-bp DNA duplex validates this SAXS computational method and suggests that DNA has a different contribution from its hydration surface to the total scattering compared to RNA and protein. To account for such a difference, a sigmoidal function is implemented for the treatment of non-uniform electron density across the surface of a protein/nucleic-acid complex. This treatment allows differential scattering from the solvation layer surrounding protein/nucleic-acid complexes. Finally, the applications of this Fast-SAXS-pro method are demonstrated for protein/DNA and protein/RNA complexes.
Show PACS
87.15.B- Structure of biomolecules
36.20.Hb Configuration (bonds, dimensions)
87.14.gk DNA
87.14.gn RNA
87.15.A- Theory, modeling, and computer simulation

A tri-atomic Renner-Teller system entangled with Jahn-Teller conical intersections

A. Csehi, A. Bende, G. J. Halász, Á. Vibók, A. Das, D. Mukhopadhyay, and M. Baer

J. Chem. Phys. 138, 024113 (2013); http://dx.doi.org/10.1063/1.4773352 (11 pages)

Online Publication Date: 14 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The present study concentrates on a situation where a Renner-Teller (RT) system is entangled with Jahn-Teller (JT) conical intersections. Studies of this type were performed in the past for contours that surround the RT seam located along the collinear axis [see, for instance, G. J. Halász, Á. Vibók, R. Baer, and M. Baer, J. Chem. Phys. 125, 094102 (2006)]. The present study is characterized by planar contours that intersect the collinear axis, thus, forming a unique type of RT-non-adiabatic coupling terms (NACT) expressed in terms of Dirac-δ functions. Consequently, to calculate the required adiabatic-to-diabatic (mixing) angles, a new approach is developed. During this study we revealed the existence of a novel molecular parameter, η, which yields the coupling between the RT and the JT NACTs. This parameter was found to be a pure number η = 2math/π (and therefore independent of any particular molecular system) and is designated as Renner-Jahn coupling parameter. The present study also reveals an unexpected result of the following kind: It is well known that each (complete) group of states, responsible for either the JT-effect or the RT-effect, forms a Hilbert space of its own. However, the entanglement between these two effects forms a third effect, namely, the RT/JT effect and the states that take part in it form a different Hilbert space.
Show PACS
33.20.Wr Vibronic, rovibronic, and rotation-electron-spin interactions
31.15.-p Calculations and mathematical techniques in atomic and molecular physics
31.30.-i Corrections to electronic structure
31.50.-x Potential energy surfaces
back to top Advanced Experimental Techniques

Direct measurements of collisionally broadened Raman linewidths of CO2 S-branch transitions

Sukesh Roy, Paul S. Hsu, Naibo Jiang, Joseph R. Gord, Waruna D. Kulatilaka, Hans U. Stauffer, and James R. Gord

J. Chem. Phys. 138, 024201 (2013); http://dx.doi.org/10.1063/1.4774093 (6 pages) | Cited 1 time

Online Publication Date: 10 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report direct measurements of S-branch Raman-coherence lifetimes of CO2 resulting from CO2–CO2 and CO2–N2 collisions by employing time-resolved picosecond coherent anti-Stokes Raman scattering spectroscopy. The S-branch (ΔJ = +2) transitions of CO2 with rotational quantum number J = 0–52 were simultaneously excited using a broadband (∼5 nm) laser pulse with a full-width-at-half-maximum duration of ∼115 ps. The coherence lifetimes of CO2 for a pressure range of 0.05–1 atm were measured directly by probing the rotational coherence with a nearly transform-limited, 90-ps-long laser pulse. These directly measured Raman-coherence lifetimes, when converted to collisional linewidth broadening coefficients, differ from the previously reported broadening coefficients extracted from frequency-domain rotational Raman and infrared-absorption spectra and from theoretical calculations by 7%–25%.
Show PACS
33.70.Jg Line and band widths, shapes, and shifts
82.53.Kp Coherent spectroscopy of atoms and molecules
33.20.Ea Infrared spectra
33.20.Fb Raman and Rayleigh spectra (including optical scattering)
33.70.Ca Oscillator and band strengths, lifetimes, transition moments, and Franck-Condon factors

Nonlinear optical absorption and stimulated Mie scattering in metallic nanoparticle suspensions

Guang S. He, Wing-Cheung Law, Alexander Baev, Sha Liu, Mark T. Swihart, and Paras N. Prasad

J. Chem. Phys. 138, 024202 (2013); http://dx.doi.org/10.1063/1.4773340 (9 pages)

Online Publication Date: 10 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The nonlinear optical properties of four metallic (Au-, Au/Ag-, Ag-, and Pt-) nanoparticle suspensions in toluene have been studied in both femtosecond and nanosecond regimes. Nonlinear transmission measurements in the femtosecond laser regime revealed two-photon absorption (2PA) induced nonlinear attenuation, while in the nanosecond laser regime a stronger nonlinear attenuation is due to both 2PA and 2PA-induced excited-state absorption. In the nanosecond regime, at input pump laser intensities above a certain threshold value, a new type of stimulated (Mie) scattering has been observed. Being essentially different from all other well known molecular (Raman, Brillouin) stimulated scattering effects, the newly observed stimulated Mie scattering from the metallic nanoparticles exhibits the features of no frequency shift and low pump threshold requirement. A physical model of induced Bragg grating initiated by the backward Mie scattering from metallic nanoparticles is proposed to explain the gain mechanism of the observed stimulated scattering effect.
Show PACS
78.47.je Time resolved light scattering spectroscopy
78.47.da Excited states
78.30.Er Solid metals and alloys
78.40.Kc Metals, semimetals, and alloys
82.70.Kj Emulsions and suspensions
back to top Atoms, Molecules, and Clusters

Ferrocene analogues of sandwich B12·Cr·B12: A theoretical study

Yuan Yuan (袁媛) and Longjiu Cheng (程龙玖)

J. Chem. Phys. 138, 024301 (2013); http://dx.doi.org/10.1063/1.4773281 (7 pages)

Online Publication Date: 8 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The bowl B12 cluster was previously reported to be analogous to benzene and predicted to be one of the best candidates to be new inorganic ligands. The structural stability and electronic properties of a new sandwich compound Cr(B12)2 (D3d) have been investigated by using density functional theory. It is found that the sandwich Cr(B12)2 (D3d) is a stable complex with large binding energy (−5.93 eV) and HOMO-LUMO gap (2.37 eV), as well as Fe(C5H5)2 and Cr(C6H6)2, following the 18-electron principle. The detailed molecular orbitals and aromaticity analyses indicate that the sandwich compound Cr(B12)2 (D3d) is electronically very stable. The natural bond orbital analysis suggests that spd-π interaction plays an important role in the sandwich compounds.
Show PACS
36.40.Cg Electronic and magnetic properties of clusters
36.40.Mr Spectroscopy and geometrical structure of clusters
31.15.E- Density-functional theory

Cascade Auger decays following Si KL23L23 Auger transitions in SiF4

I. H. Suzuki, Y. Kono, A. Ikeda, M. Oi, T. Ouchi, K. Ueda, Y. Tamenori, O. Takahashi, and S. Nagaoka

J. Chem. Phys. 138, 024302 (2013); http://dx.doi.org/10.1063/1.4773344 (7 pages)

Online Publication Date: 8 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Cascade Si LVV Auger decays following KL23L23 Auger transitions have been measured in SiF4 molecule using an electron spectrometer combined with monochromatized undulator radiation. Molecular cascade processes from the two 2p holes states largely generate wide band structures in the spectra due to sequential electron emission leading to multiple valence holes. However, a peak with high yield is observed for the first time at about 103 eV, an energy being considerably higher than the energies of the normal LVV Auger electron, in the instance of the resonant excitation of Si 1s electron into the vacant molecular orbital. This peak is presumed to originate from the participator decay from the state with two 2p holes and one excited electron into the state with one 2p hole and one valence hole. A similar peak with less intensity is detected in the photoexcitation of the 1s electron into a Rydberg orbital. After the normal KL23L23 Auger transition, the resultant cascade spectrum shows several peaks, e.g., 61 eV, 76 eV, and 82 eV. The former two peaks are assigned to the Auger transitions of Si atoms produced through molecular ion dissociation after cascade decays, and the latter is probably ascribed to the second step Auger decay into states having a 2p hole together with two valence holes.
Show PACS
33.80.Eh Autoionization, photoionization, and photodetachment
33.80.Gj Diffuse spectra; predissociation, photodissociation
33.60.+q Photoelectron spectra
33.70.Fd Absolute and relative line and band intensities

Structural studies of aromatic carboxylic acids via computational chemistry and microwave spectroscopy

Peter D. Godfrey and Don McNaughton

J. Chem. Phys. 138, 024303 (2013); http://dx.doi.org/10.1063/1.4773347 (8 pages)

Online Publication Date: 8 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The structures of three simple aromatic carboxylic acids: benzoic, isophthalic, and terephthalic have been investigated using a combination of theoretical high-level quantum chemical calculations and experimental millimeter-wave Stark-modulated free-jet absorption spectroscopy. Rotational and centrifugal distortion constants have been measured for one conformer of each of the species and for its –COOD isotopologue, leading to the experimental determination of the coordinates of the carboxyl hydrogen atom. Consideration of the observed inertial defect is consistent with a planar equilibrium structure for each species. Calculated structures, relative energies, and electric dipole moments, using ab initio methods at the MP2/cc-pVTZ level, are reported for all the lower-energy conformers of each species. The theoretical calculations lead to the unambiguous identification of the conformers involved in the observed microwave spectra. The match between theoretical and spectroscopic measurements was used to gauge the reliability of the quantum chemical structure optimization calculations.
Show PACS
31.15.am Relativistic configuration interaction (CI) and many-body perturbation calculations
33.15.Bh General molecular conformation and symmetry; stereochemistry
33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.20.Bx Radio-frequency and microwave spectra
33.20.Sn Rotational analysis

Quantum control of multi-photon dissociation of HCl+ with intense femtosecond laser pulses

Qianzhen Su, Yongchang Han, and Shu-lin Cong

J. Chem. Phys. 138, 024304 (2013); http://dx.doi.org/10.1063/1.4773022 (8 pages)

Online Publication Date: 8 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The multi-photon dissociation of HCl+ through three channels HCl +→H(1s|2S)+ Cl +(3P), H++ Cl (2P0), and H(2S)+ Cl +(1D) steered by intense femtosecond laser pulses are investigated theoretically using the quantum wave packet dynamics. The numerical calculations are performed in two cases without and with the coupling between the excited states. The results show that the dissociation is sensitive to the duration τ, peak intensity I0, and the resonance of driving laser fields. In the case without the coupling, the effect of the permanent dipole moments on the dissociations dominates for τ < 15 fs, while with the increase of τ, the dissociation dynamics is mainly dominated by the transition dipole moment. In the case with the coupling, the above-threshold dissociation process is complex, and the non-resonant (λ = 400 nm) and resonant (λ = 800 and 1200 nm) laser fields lead to different variation of the branching ratios. The angle-resolved energy distribution is also discussed in detail.
Show PACS
33.80.Gj Diffuse spectra; predissociation, photodissociation
33.80.Rv Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states)
31.15.-p Calculations and mathematical techniques in atomic and molecular physics
33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility
33.70.Ca Oscillator and band strengths, lifetimes, transition moments, and Franck-Condon factors
33.70.Fd Absolute and relative line and band intensities
Page 1 of 3 Pages Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close