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8 Jan 2003

Volume 118, Issue 2, pp. 457-996

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Analytic continuation for quantum nonadiabatic rate constants

Andrei A. Golosov, David R. Reichman, and Eran Rabani

J. Chem. Phys. 118, 457 (2003); http://dx.doi.org/10.1063/1.1535214 (4 pages) | Cited 20 times

Online Publication Date: 20 December 2002

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We develop a method for calculating nonadiabatic rate constants in condensed phases. The method is based on a novel path integral representation of the imaginary time flux–flux correlation function combined with an analytic continuation technique. The method is general, and may be applied to systems with arbitrarily strong coupling parameters, arbitrary anharmonic environments and any number of discrete system states. The method is applied to a nontrivial benchmark system with encouraging results. © 2003 American Institute of Physics.
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82.20.Pm Rate constants, reaction cross sections, and activation energies
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back to top Theoretical Methods and Algorithms

Connections between second-order Görling–Levy and many-body perturbation approaches in density functional theory

Stanislav Ivanov, So Hirata, Ireneusz Grabowski, and Rodney J. Bartlett

J. Chem. Phys. 118, 461 (2003); http://dx.doi.org/10.1063/1.1522570 (10 pages) | Cited 12 times

Online Publication Date: 20 December 2002

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Formal connections between the high-density scaling limit of the correlation energy functional Ec[n] in density functional theory and second-order energy expressions from different perturbation theory formulations are presented. It is demonstrated that the second-order correlation potential considered by Grabowski et al. [J. Chem. Phys. 116, 4415 (2002)] is equivalent to the high-density limit of the exact correlation potential, and thus provides the first self-consistent finite-basis-set implementation of a Kohn–Sham (KS) potential correct through second-order. A different second-order correlation functional based on the exchange-only KS approach is introduced. It is shown that this second-order correlation functional leads to the same self-consistent KS realization as the one derived from the second-order component of Ec[n]. © 2003 American Institute of Physics.
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31.15.E- Density-functional theory
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
31.15.xp Perturbation theory

Relativistic effects on the nuclear magnetic shielding tensor

J. I. Melo, M. C. Ruiz de Azua, C. G. Giribet, G. A. Aucar, and R. H. Romero

J. Chem. Phys. 118, 471 (2003); http://dx.doi.org/10.1063/1.1525808 (16 pages) | Cited 31 times

Online Publication Date: 20 December 2002

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A new approach for calculating relativistic corrections to the nuclear magnetic shieldings is presented. Starting from a full relativistic second order perturbation theory expression a two-component formalism is constructed by transforming matrix elements using the elimination of small component scheme and separating out the contributions from the no-virtual pair and the virtual pair part of the second order corrections to the energy. In this way we avoid a strong simplification used previously in the literature. We arrive at final expressions for the relativistic corrections which are equivalent to those of Fukui et al. [J. Chem Phys. 105, 3175 (1996)] and at some other additional terms correcting both the paramagnetic and the diamagnetic part of the nuclear magnetic shielding. Results for some relativistic corrections to the shieldings of the heavy and light nuclei in HX and CH3X (X = Br,I) at both random phase and second order polarization propagator approach levels are given. © 2003 American Institute of Physics.
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31.30.J- Relativistic and quantum electrodynamic (QED) effects in atoms, molecules, and ions
33.25.+k Nuclear resonance and relaxation

Valence basis sets for relativistic energy-consistent small-core actinide pseudopotentials

Xiaoyan Cao, Michael Dolg, and Hermann Stoll

J. Chem. Phys. 118, 487 (2003); http://dx.doi.org/10.1063/1.1521431 (10 pages) | Cited 55 times

Online Publication Date: 20 December 2002

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Gaussian (14s13p10d8f6g)/[6s6p5d4f3g] atomic natural orbital valence basis sets have been generated for relativistic energy-consistent small-core actinide pseudopotentials of the Stuttgart–Bonn variety. Effective valence spin–orbit operators supplementing the scalar-relativistic pseudopotentials have been derived from multiconfiguration Dirac–Hartree–Fock reference data. Pseudopotentials, basis sets and spin–orbit operators have been used to determine the first and second ionization potentials of all actinide elements at the multiconfiguration self-consistent field and multireference averaged coupled-pair functional level. Comparison is made to results obtained from large-scale calculations using uncontracted basis sets up to i-type functions and extrapolation to the basis set limit as well as to experimental data. Molecular calibration studies using the coupled-cluster singles, doubles, and perturbative triples approach are reported for the ground states of AcH, AcO, AcF, and ThO. © 2003 American Institute of Physics.
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31.30.J- Relativistic and quantum electrodynamic (QED) effects in atoms, molecules, and ions
31.15.xr Self-consistent-field methods
33.15.Ry Ionization potentials, electron affinities, molecular core binding energy

Molecular motors driven by laser pulses: Role of molecular chirality and photon helicity

Kunihito Hoki, Masahiro Yamaki, Shiro Koseki, and Yuichi Fujimura

J. Chem. Phys. 118, 497 (2003); http://dx.doi.org/10.1063/1.1526834 (8 pages) | Cited 16 times

Online Publication Date: 20 December 2002

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The results of a theoretical study on molecular motors driven by laser pulses are presented. The roles of molecular chirality and photon helicity in determination of their unidirectional rotation are clarified. An expression for an instantaneous angular momentum of motors driven by lasers in the density matrix formalism was derived. Assuming randomly oriented molecular motors, the initial distribution-averaged instantaneous angular momentum in the dipole approximation was obtained. Taking into account parity inversion symmetry of molecular motors in the averaged instantaneous angular momentum, it is shown that the directions of the averaged instantaneous angular momentum of (R)- and (S)-chiral molecular motors are opposite, but that the magnitudes are the same. This is independent of polarization of laser fields. That is, the chiral motors driven by a linearly polarized optical field creates a unidirectional motion in a molecular fixed frame. On the other hand, the direction of rotation in the laboratory fixed frame is decided by a circularly polarized laser regardless of its molecular chirality. A simple example of real chiral molecular motors is used to demonstrate the interplay of molecular chirality and photon helicity in determination of their unidirectional rotation. The internal rotation of the CHO group plays the role of the engine of the motor. The time evolution of the rotational wave packets of the molecular motors driven by linearly or circularly polarized laser pulses was numerically evaluated and the dynamical behaviors were analyzed. Effects of temperature on the instantaneous angular momentum of the molecular motors are presented as well. © 2003 American Institute of Physics.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
33.80.-b Photon interactions with molecules
33.15.Bh General molecular conformation and symmetry; stereochemistry

Analytical time-dependent Hartree-Fock evaluation of the dynamic zero-point vibrationally averaged (ZPVA) first hyperpolarizability

Oliver Quinet, Bernard Kirtman, and Benoît Champagne

J. Chem. Phys. 118, 505 (2003); http://dx.doi.org/10.1063/1.1523903 (9 pages) | Cited 10 times

Online Publication Date: 20 December 2002

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A procedure to compute analytical second derivatives of the dynamic first hyperpolarizability with respect to vibrational coordinates has been developed and implemented at the time-dependent Hartree-Fock level. Simplifications are obtained by the same techniques as those employed to derive the 2n+1 rule and the interchange relations. This scheme is used to determine the first-order ZPVA correction for three small molecules. It is found that the frequency dispersion coefficients are similar to those obtained for the pure electronic contribution in H2O and NH3 but not CH4. © 2003 American Institute of Physics.
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33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility
31.15.xr Self-consistent-field methods
33.20.Tp Vibrational analysis

A discrete solvent reaction field model within density functional theory

Lasse Jensen, Piet Th. van Duijnen, and Jaap G. Snijders

J. Chem. Phys. 118, 514 (2003); http://dx.doi.org/10.1063/1.1527010 (8 pages) | Cited 30 times

Online Publication Date: 20 December 2002

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In this work we present theory and implementation for a discrete reaction field model within Density Functional Theory (DFT) for studying solvent effects on molecules. The model combines a quantum mechanical (QM) description of the solute and a classical description of the solvent molecules (MM). The solvent molecules are modeled by point charges representing the permanent electronic charge distribution, and distributed polarizabilities for describing the solvent polarization arising from many-body interactions. The QM/MM interactions are introduced into the Kohn–Sham equations, thereby allowing for the solute to be polarized by the solvent and vice versa. Here we present some initial results for water in aqueous solution. It is found that the inclusion of solvent polarization is essential for an accurate description of dipole and quadrupole moments in the liquid phase. We find a very good agreement between the liquid phase dipole and quadrupole moments obtained using the Local Density Approximation and results obtained with a similar model at the Coupled Cluster Singles and Doubles level of theory using the same water cluster structure. The influence of basis set and exchange correlation functional on the liquid phase properties was investigated and indicates that for an accurate description of the liquid phase properties using DFT a good description of the gas phase dipole moment and molecular polarizability are also needed. © 2003 American Institute of Physics.
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31.15.E- Density-functional theory
31.15.bw Coupled-cluster theory
32.30.-r Atomic spectra
33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility

Linear response at the 4-component relativistic level: Application to the frequency-dependent dipole polarizabilities of the coinage metal dimers

T. Saue and H. J. Aa. Jensen

J. Chem. Phys. 118, 522 (2003); http://dx.doi.org/10.1063/1.1522407 (15 pages) | Cited 40 times

Online Publication Date: 20 December 2002

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Linear response theory based on the time-averaged quasienergy of Floquet states is generalized to the 4-component relativistic level for molecular calculations based on an analytical basis set. An efficient implementation of the theory for 4-component closed-shell Hartree–Fock is described. This level of approximation is also called the 4-component relativistic random phase approximation. The structure of the reduced response equations is analyzed in terms of Hermiticity and time reversal symmetry and leads to restrictions on the form chosen for the trial vectors as well as rules indicating when the linear response function is real, imaginary or zero. A key ingredient of the AO-driven algorithm is the formulation of the Hessian times a trial vector as the construction of modified Fock matrices. To reduce computational cost a previously reported quaternion symmetry scheme has been extended to non totally symmetric operators such that possible symmetry reductions are obtained as a reduction of algebra from quaternion to complex or real. We report the calculations of the frequency-dependent dipole polarizabilities for Cu2, Ag2, and Au2 at the 4-component Dirac–Coulomb Hartree–Fock level. Comparison of the relativistic and non-relativistic results show an increasing discrepancy with increasing nuclear charge, leading to qualitatively different results. Analysis of the first-order wave function shows that in the case of the gold dimer at the relativistic level of theory the generally dominant excitations from the HOMO are supplemented by excitations from the 5d manifold. This may significantly alter the molecular spectra and will be studied in a subsequent paper. © 2003 American Institute of Physics.a
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31.30.J- Relativistic and quantum electrodynamic (QED) effects in atoms, molecules, and ions
31.15.xr Self-consistent-field methods
33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility

Counterpoise-corrected geometries and harmonic frequencies of N-body clusters: Application to (HF)n (n = 3,4)

Pedro Salvador and Małgorzata M. Szczȩśniak

J. Chem. Phys. 118, 537 (2003); http://dx.doi.org/10.1063/1.1527011 (13 pages) | Cited 14 times

Online Publication Date: 20 December 2002

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The differences between three previously defined counterpoise (CP) schemes for removing the BSSE in molecular complexes formed by more than two subunits have been assessed by CP-corrected geometry optimizations and frequency calculations for the hydrogen fluoride trimer and tetramer. The types of the functional counterpoise (FC) procedures included the site–site (SSFC), pairwise additive, and hierarchical Valiron–Mayer (VMFC) schemes. The latter approach takes into account the basis set extension of the dimers in the trimer, dimers and trimers in the tetramer, etc. The number of different calculations required to apply this counterpoise scheme increases very rapidly with the cluster size. The symmetry of the chosen systems makes the test of this approach computationally feasible. All the optimizations and frequency calculations have been carried out automatically using a new program that generates the necessary input files and repeatedly calls a slightly modified version of a Gaussian link. The results show that geometrical parameters, zero-point vibrational energies, and redshifts computed on the CP-corrected potential energy surfaces differ considerably from those evaluated on the uncorrected surfaces. The structural and energetic properties obtained with the conventional SSFC procedure are almost identical to those predicted by the more costly and complex VMFC method. Hence, the former seems to be more appropriate in the present case. Furthermore, symmetry-adapted perturbation theory calculations show the importance of computing the interaction energies at the CP-corrected geometries. © 2003 American Institute of Physics.
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36.40.Mr Spectroscopy and geometrical structure of clusters
36.40.Sx Diffusion and dynamics of clusters
33.15.Mt Rotation, vibration, and vibration-rotation constants
31.15.xp Perturbation theory
back to top Gas Phase Dynamics and Structure: Spectroscopy, Molecular Interactions, Scattering, and Photochemistry

Electronic and photophysical properties of C60Cl24

P. F. Coheur, J. Liévin, R. Colin, and B. Razbirin

J. Chem. Phys. 118, 550 (2003); http://dx.doi.org/10.1063/1.1525807 (7 pages) | Cited 5 times

Online Publication Date: 20 December 2002

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This work examines, by using quantum-chemical calculations, the electronic and optical properties of three highly symmetrical isomers of the C60Cl24 halogenofullerene. The ground state properties of these derivatives are calculated using the semi-empirical Hartree–Fock AM1 approach and discussed in terms of symmetry, charge distribution and electronic conjugation on the fullerene cage. Starting from the optimized geometry, the optical absorption spectrum of each molecule is calculated at the semi-empirical Hartree–Fock INDO/S level, using a large configuration interaction scheme. The results are compared to a visible and near-infrared absorption spectrum of C60Cl24, recorded in solid matrices, at low temperature. From the comparison, it is concluded that a D2h C60Cl24 isomer is responsible for the spectrum observed. The spectrum is analyzed in terms of electronic singlet transitions. © 2003 American Institute of Physics.
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36.40.Cg Electronic and magnetic properties of clusters
36.40.Mr Spectroscopy and geometrical structure of clusters
33.20.Kf Visible spectra
33.20.Ea Infrared spectra
31.15.xr Self-consistent-field methods
31.15.bu Semi-empirical and empirical calculations (differential overlap, Hückel, PPP methods, etc.)
31.15.vq Electron correlation calculations for polyatomic molecules

A computational study of chlorofluoro-methyl radicals

M. Schwartz, L. R. Peebles, R. J. Berry, and Paul Marshall

J. Chem. Phys. 118, 557 (2003); http://dx.doi.org/10.1063/1.1524157 (8 pages) | Cited 8 times

Online Publication Date: 20 December 2002

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Chorine- and fluorine-containing methyl radicals have been investigated by ab initio methods. Geometries and vibrational frequencies were derived with quadratic configuration methods at the QCISD/6-311G(d,p) level of theory, and energies via QCISD(T)/6-311+G(3df,2p) and Gaussian 3 theory. Anharmonicity of the out of plane bending mode was taken into account by numerical integration of the Schrödinger equation with a potential derived from a relaxed scan of this mode. The results are in good accord with experimental data where available. For the radicals CHF2, CF3, CH2Cl, CHCl2, and CCl3, we compute ΔfH2980 values of −241.2, −465.9, 117.0, 91.1, and 72.2 kJ mol−1, respectively, which agree with well-established experimental values to within 2.2 kJ mol−1. For the more poorly characterized molecules CH2F, CHClF, CClF2, and CCl2F we compute ΔfH2980 values of −29.0, −63.8, −274.7, and −94.3 kJ mol−1, respectively, with recommended confidence limits of ±4.1 kJ mol−1. © 2003 American Institute of Physics.
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31.15.A- Ab initio calculations
31.15.xp Perturbation theory
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.15.Bh General molecular conformation and symmetry; stereochemistry
31.15.vq Electron correlation calculations for polyatomic molecules

Quantum mechanical and quasi-classical trajectory study of the C(1D)+H2 reaction dynamics

L. Bañares, F. J. Aoiz, P. Honvault, B. Bussery-Honvault, and J.-M. Launay

J. Chem. Phys. 118, 565 (2003); http://dx.doi.org/10.1063/1.1527014 (4 pages) | Cited 102 times

Online Publication Date: 20 December 2002

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First accurate quantum mechanical (QM) calculations of integral and differential cross sections for the C(1D)+H2(v = 0,j = 0,1) insertion reaction have been performed on a newly developed ab initio potential energy surface [B. Bussery-Honvault et al., J. Chem. Phys. 115, 10701 (2001)]. These results have been compared with those obtained with a quasi-classical trajectory (QCT) method. A Gaussian-weighted binning procedure to assign product quantum states in the QCT calculations yields vibrational branching ratios and rotational distributions in better agreement with the QM calculations than those obtained when the usual histogramatic binning method is employed. This is the first time that the Gaussian-weighted binning procedure is used for an insertion reaction. © 2003 American Institute of Physics.
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82.20.Fd Collision theories; trajectory models
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions

Quantum reactive scattering in three dimensions using adiabatically adjusting principal axis hyperspherical coordinates: Periodic distributed approximating functional method for surface functions

Keming Zhang, Gregory A. Parker, Donald J. Kouri, David K. Hoffman, and Srinivasan S. Iyengar

J. Chem. Phys. 118, 569 (2003); http://dx.doi.org/10.1063/1.1526835 (13 pages) | Cited 1 time

Online Publication Date: 20 December 2002

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Periodic distributed approximating functionals are proposed and used to obtain a coordinate representation for the adiabatically adjusting principal axis hyperspherical coordinate kinetic energy operator. The approach is tested and accurate results for adiabatic surface functions for the reaction F+H2→HF+H are calculated and compared to those of some existing methods. © 2003 American Institute of Physics.
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82.20.Kh Potential energy surfaces for chemical reactions
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)
02.60.Dc Numerical linear algebra

Analytical fittings for the global potential energy surface of the ground state of methylene

Jen-Shiang K. Yu, Sue-ying Chen, and Chin-Hui Yu

J. Chem. Phys. 118, 582 (2003); http://dx.doi.org/10.1063/1.1523906 (13 pages) | Cited 2 times

Online Publication Date: 20 December 2002

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The global potential energy surface (PES) corresponding to the dissociation reaction of the ground state of methylene (CH2) is studied with the coupled-cluster method with single, double and perturbative triplet excitations, CCSD(T), in conjunction with the correlation-consistent cc-pVTZ basis set, and fitted by three analytical potential functions in terms of the Simons–Parr–Finlan (SPF) polynomial, Jensen function and the Sorbie–Murrell (SM) function. Ab initio single-point calculations over a distributed range of grids are performed first, and totally 12 085 converged points are fed into these functions. The fitting of each analytical PES function is done with an unconstrained minimization of the difference between the evaluations of the analytical function and the ab initio results, solved by a modified Levenberg–Marquardt algorithm with a finite-difference Jacobian in the IMSL package. The SPF polynomial is found to have the best global description, while the SM function behaves superior in the dissociation region forming three atoms. The spline function is potentially feasible to interpolate the computationally divergent points in the ab initio calculations. © 2003 American Institute of Physics.
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31.50.Bc Potential energy surfaces for ground electronic states
31.15.bw Coupled-cluster theory
31.15.xf Finite-difference schemes
31.15.A- Ab initio calculations

Control of vibrational ionization branching through feedback-optimized tailored femtosecond laser pulses

E. Hertz, G. Nersisyan, N. A. Papadogiannis, and D. Charalambidis

J. Chem. Phys. 118, 595 (2003); http://dx.doi.org/10.1063/1.1524621 (5 pages) | Cited 8 times

Online Publication Date: 20 December 2002

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We report the control of the ionization yield ratio to different vibrational levels of the electronic ground state of NO+ by feedback optimization of shaped ultra-short laser pulses. The nitric oxide NO molecule is excited by the second harmonic of a phase-shaped Ti:sapphire femtosecond laser. The optimization of pulse tailoring by a learning evolutionary algorithm leads to significant modifications of the vibrational ionic distribution observed by photoelectron spectroscopy. The control exerted over two groups of photoelectrons is robust and reveals some selectivity. © 2003 American Institute of Physics.
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33.80.Eh Autoionization, photoionization, and photodetachment
33.60.+q Photoelectron spectra
33.15.Mt Rotation, vibration, and vibration-rotation constants

Photodissociation of the ArHBr complex investigated with the multiconfiguration time-dependent Hartree approach

J. Trin, M. Monnerville, B. Pouilly, and H.-D. Meyer

J. Chem. Phys. 118, 600 (2003); http://dx.doi.org/10.1063/1.1523013 (10 pages) | Cited 13 times

Online Publication Date: 20 December 2002

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We apply the multiconfiguration time-dependent Hartree method to the study of the photodissociation of the Ar–HBr van der Waals complex. The dynamics is studied in both Jacobi and valence coordinates. The evolution of the probability density in the different modes shows that the direct or nearly direct mechanism, where the hydrogen atom interacts only very weakly with the Ar and Br atoms, dominates the dissociation process. By projecting the quantum flux onto the vibrational levels of ArBr, we find at the maximum of the absorption profile, i.e., around E = 3 eV, that 65% of the dissociation gives rise to partial fragmentation into hot H fragments and bound ArBr molecules. © 2003 American Institute of Physics.
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33.80.Gj Diffuse spectra; predissociation, photodissociation
31.15.xr Self-consistent-field methods
82.50.Hp Processes caused by visible and UV light

Theoretical investigation of the temperature dependence of the O+O2 exchange reaction

Paul Fleurat-Lessard, Sergy Yu. Grebenshchikov, Rüdiger Siebert, Reinhard Schinke, and Nadine Halberstadt

J. Chem. Phys. 118, 610 (2003); http://dx.doi.org/10.1063/1.1525255 (12 pages) | Cited 40 times

Online Publication Date: 20 December 2002

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The exchange reaction 16O+18O2→16O18O+18O and, in particular, its dependence on the transition state region is investigated by classical trajectories on three potential energy surfaces, all based on high-level electronic structure calculations. The first one is the original potential recently constructed by Siebert, Schinke, and Bittererová [Phys. Chem. Chem. Phys. 3, 1795 (2001)]; it has a very small barrier above the O+O2 asymptote. The second potential is a modification of the first one in that the transition state region is adjusted according to new electronic structure calculations on higher levels of theory; it has a small barrier below the asymptote. The third potential is obtained by artificially removing this barrier. The variation of the exchange reaction cross section with collision energy and the magnitude of the thermal rate constant at and below room temperature depend drastically on the shape of the potential at intermediate distances. The second potential, which is believed to represent the transition state structure of the true ground-state potential of ozone best, yields a reaction rate for room temperature that is about a factor of three smaller than the experimental rate. The neglect of nonadiabatic transitions between the several electronic states in the entrance channel may explain this discrepancy. The very slight negative temperature dependence found in the calculations is caused by the strong decrease of the reaction cross section with the initial rotational excitation of the oxygen molecule. Statistical calculations give poor agreement with the classical energy and initial-state dependent cross sections. Nevertheless, the statistical thermal rates are in fair agreement with the classical ones, because the overestimation of the cross sections for low j’s and the underestimation for high j’s partly compensate. © 2003 American Institute of Physics.
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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)
82.20.Kh Potential energy surfaces for chemical reactions
82.20.Pm Rate constants, reaction cross sections, and activation energies
32.10.Bi Atomic masses, mass spectra, abundances, and isotopes

CF A 2Σ+–X 2Π and B 2Δ–X 2Π study by broadband absorption spectroscopy in a plasma etch reactor: Determination of transition probabilities, CF X 2Π concentrations, and gas temperatures

Jorge Luque, Eric A. Hudson, and Jean-Paul Booth

J. Chem. Phys. 118, 622 (2003); http://dx.doi.org/10.1063/1.1527923 (11 pages) | Cited 13 times

Online Publication Date: 20 December 2002

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Broadband absorption spectroscopy was applied to study the CF A 2Σ+–X 2Π and B 2Δ–X 2Π transitions in a plasma etch reactor. We report a previously unobserved band, which is assigned as CF A 2Σ+–X 2Π (3,0). This band is significantly broadened by predissociation, and we estimate the average collision-free lifetime of the CF A 2Σ+ v′ = 3 level to be 0.30±0.08 ps. Experimental relative oscillator strength measurements, together with ab initio calculations, Rydberg–Klein–Rees-based wave functions and experimental lifetimes were used to calculate a full set of transition probabilities for the CF A 2Σ+–X 2Π and B 2Δ–X 2Π bands. The maximum observed number densities of CF X 2Π were ∼ 2×1013 cm−3 with sensitivity to measure to 1010 cm−3. The excited state and ground state temperatures were determined by comparing the spectra to simulations. The ground state rotational temperature was 450±30 K and the vibrational temperature was 850±80 K near the substrate surface. The CF B 2Δ excited state rotational temperatures are higher than those of the ground state. We show that this absorption technique is practical for determining gas temperatures and absolute concentrations in plasma etch reactors. © 2003 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
33.70.Ca Oscillator and band strengths, lifetimes, transition moments, and Franck-Condon factors
33.20.Lg Ultraviolet spectra
52.25.-b Plasma properties
31.15.A- Ab initio calculations
33.80.Gj Diffuse spectra; predissociation, photodissociation
52.77.Bn Etching and cleaning
52.75.-d Plasma devices
33.70.Fd Absolute and relative line and band intensities

Kinetic and mechanistic studies on the abstraction reactions of atomic O (3P) with (CH3)2SiH2 and (CH3)3SiH

Qingzhu Zhang, Yueshu Gu, and Shaokun Wang

J. Chem. Phys. 118, 633 (2003); http://dx.doi.org/10.1063/1.1523904 (10 pages) | Cited 3 times

Online Publication Date: 20 December 2002

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The reactions of atomic O (3P) with (CH3)2SiH2 and (CH3)3SiH have been studied theoretically using ab initio molecular orbital theory for the first time. Geometries have been optimized at the MP2 level with the 6-311G(d,p) and 6-311G(2d,2p) basis sets. The single-point energy calculations have been carried at the QCISD(T)/6-311+G(3df,2p) level. Theoretical analysis provides conclusive evidence that the main process occurring in each reaction is the hydrogen abstraction from the Si–H bonds leading to the formation of the H2 and silyl radical; the hydrogen abstraction from the C–H bonds has higher barrier and is difficult to react. Two nearly degenerate transition states of 3A″ and 3A′ symmetries have been located for each hydrogen abstraction reaction from the Si–H bonds. Changes of geometries, generalized normal-mode vibrational frequencies, and potential energies along the reaction paths are discussed and compared. The rate constants have been deduced over a wide temperature range of 200–3000 K using canonical variational transition-state theory (CVT) with small curvature tunneling effect (SCT). The calculated CVT/SCT rate constants exhibit typical non-Arrhenius behavior, three-parameter rate-temperature formulas are fitted as follows (in units of cm3 molecule−1 s−1): k1(T) = (3.41×10−16)T1.65exp(−411.72/T) and k2(T) = (1.85×10−15)T1.42 exp(−372.57/T) for the reactions of O (3P) with (CH3)2SiH2 and (CH3)3SiH, respectively. The calculated rate constants are compared with the available experimental values. © 2003 American Institute of Physics.
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82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
82.20.Pm Rate constants, reaction cross sections, and activation energies

Tunneling dynamics of the NH chromophore in NHD2 during and after coherent infrared excitation

Roberto Marquardt, Martin Quack, Ioannis Thanopulos, and David Luckhaus

J. Chem. Phys. 118, 643 (2003); http://dx.doi.org/10.1063/1.1514577 (16 pages) | Cited 18 times

Online Publication Date: 20 December 2002

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The time dependent quantum dynamics of the large amplitude motion of the NH stretching chromophore in NHD2 is investigated during and after coherent multiphoton excitation by calculation of the wave packet evolution using global analytical potential energy and electric dipole hypersurfaces of ammonia derived from ab initio calculations. Intramolecular vibrational redistribution between the NH stretching and bending motion and coupling to the radiation field induces a diffusion of probability density into the NH chromophore space, which includes the inversion coordinate. However, inversion remains essentially dominated by a tunneling process, even at average energies well above the inversion barrier. © 2003 American Institute of Physics.
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33.80.-b Photon interactions with molecules
33.20.Tp Vibrational analysis

Intramolecular vibrational energy redistribution, mode specificity, and nonexponential unimolecular decay dynamics of vibrationally highly excited states of DCO (math 2A′)

F. Renth, F. Temps, and A. Tröllsch

J. Chem. Phys. 118, 659 (2003); http://dx.doi.org/10.1063/1.1525256 (10 pages) | Cited 3 times

Online Publication Date: 20 December 2002

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The unimolecular dynamics of vibrationally highly excited states of DCO (math 2A′) in the energy region up to Evib ⩽ 9500 cm−1, beyond the D–CO (math) dissociation threshold, has been investigated using an effective polyad Hamiltonian obtained by fitting to the term energies from the measured math 2A′←math 2A′ stimulated emission pumping (SEP) spectra of the molecule [Stöck et al., J. Chem. Phys. 106, 5333 (1997); Temps and Tröllsch, Z. Phys. Chem. 215, 207 (2001)]. An added absorbing negative imaginary potential allowed for the unimolecular dissociation of the highly excited DCO via distinctive open reaction channels of the DC stretching vibration. The ensuing dynamics was explored using a wave packet propagation approach. Time profiles describing the intramolecular vibrational energy redistribution (IVR) and unimolecular decay kinetics were computed for the CO stretching zero-order basis states up to 6 quanta of excitation and the DCO bending zero-order basis states up to 12 quanta of excitation. The computed decay curves for the CO stretching zero-order basis states compare nicely with those of the respective coherent superposition states constructed directly from the measured SEP spectra (assuming the CO stretching mode as the Franck–Condon active bright zero-order mode that determines the observed transitions). A comparison of the decay curves with those of the almost isoenergetic DCO bending zero-order basis states in the respective polyads reveals large differences in the couplings of the two vibrational modes among each other and with the open dissociation channels. The obtained unimolecular decay profiles exhibit pronounced non-exponential kinetics. Comparison with statistically calculated decay rates shows a substantial degree of mode specificity of the dynamics, which can be attributed to a bottleneck in the IVR from the CO stretching vibration to the reaction coordinate. The model calculations explain the two-to-three orders of magnitude large difference between the measured eigenstate specific DCO (math) decay constants [Stöck et al.] and predictions by microcanonical statistical rate theories. © 2003 American Institute of Physics.
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34.50.Ez Rotational and vibrational energy transfer
33.15.Hp Barrier heights (internal rotation, inversion, rotational isomerism, conformational dynamics)
back to top Condensed Phase Dynamics, Structure, and Thermodynamics: Spectroscopy, Reactions, and Relaxation

Rigorous calculation of electric field effects on the free energy change of the electron transfer reaction

Kazuhiko Seki, S. D. Traytak, and M. Tachiya

J. Chem. Phys. 118, 669 (2003); http://dx.doi.org/10.1063/1.1527632 (11 pages) | Cited 6 times

Online Publication Date: 20 December 2002

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We theoretically investigate the effect of an external electric field on the free energy change of electron transfer reaction in polar solvents. The external electric field produces polarization both on the solutes and in the solvent. Since the polarization produced on the solute differs from that in the solvent, apparent surface charge is created on the surface of the solutes. The polarization charge on the surface of the solutes interacts with the charge associated with the electron transfer. The free energy change of the reaction including such effect is calculated rigorously. A simple formula is derived and compared to the exact result in the case of spherical solutes in the dielectric continuum media. Only slight deviations are observed for any values of the solvent polarity and of the ratio between the radii of the donor and the acceptor molecules. In addition, we also applied the same method to evaluate the reorganization energy rigorously: The Marcus expression for the reorganization energy is an approximate one. The accuracy of the Marcus expression is assessed by comparing it with the exact result. © 2003 American Institute of Physics.
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82.20.Yn Solvent effects on reactivity
82.60.Lf Thermodynamics of solutions
82.30.-b Specific chemical reactions; reaction mechanisms
82.20.Pm Rate constants, reaction cross sections, and activation energies
65.20.-w Thermal properties of liquids

Physical limit of stability in supercooled D2O and D2O+H2O mixtures

S. B. Kiselev and J. F. Ely

J. Chem. Phys. 118, 680 (2003); http://dx.doi.org/10.1063/1.1526634 (10 pages) | Cited 6 times

Online Publication Date: 20 December 2002

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The fluctuation theory of homogeneous nucleation was applied for calculating the physical boundary of metastable states, the kinetic spinodal, in supercooled D2O and D2O+H2O mixtures. The kinetic spinodal in our approach is completely determined by the surface tension and equation of state of the supercooled liquid. We developed a crossover equation of state for supercooled D2O, which predicts a second critical point of low density water–high density water equilibrium, CP2, and represents all available experimental data in supercooled D2O within experimental accuracy. Using Turnbull’s expression for the surface tension we calculated with the crossover equation of state for supercooled D2O the kinetic spinodal, TKS, which lies below the homogeneous nucleation temperature, TH. We show that CP2 always lies inside in the so-called “nonthermodynamic habitat” and physically does not exist. However, the concept of a second “virtual” critical point is physical and very useful. Using this concept we have extended this approach to supercooled D2O+H2O mixtures. As an example, we consider here an equimolar D2O+H2O mixture in normal and supercooled states at atmospheric pressure, P = 0.1 MPa. © 2003 American Institute of Physics.
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05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion
64.60.Q- Nucleation
82.60.Nh Thermodynamics of nucleation

Modeling velocity autocorrelation functions of confined fluids: A memory function approach

S. H. Krishnan and K. G. Ayappa

J. Chem. Phys. 118, 690 (2003); http://dx.doi.org/10.1063/1.1524191 (16 pages) | Cited 13 times

Online Publication Date: 20 December 2002

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Velocity autocorrelation functions (VACF) of a fluid confined in a slit pore have been modeled using the memory equation. Models for the VACF are based on both the truncation and analytic closure approximations of the Mori’s continued fraction representation. The performance of the models is evaluated for gas to liquid-like pore densities and pore widths which accommodate one to four atomic layers. In all cases we compare the predictions from the models with the VACF obtained from molecular dynamics simulations. The truncation models predict an oscillatory behavior for the in-plane VACF with better agreement at lower densities. Among the analytical closure models we observe that the sech model applied at the first level of closure is not only able to capture the short-time dynamics but is also seen to give the best predictions to the in-plane diffusivities at liquid-like pore densities. Although the minima in the VACFs are captured accurately by the sech model, the subsequent plateau regions in the VACF typically observed in confined systems are not predicted. This aspect is due to the slower relaxation of the actual memory kernel, which is not captured by the model. Predictions of the in-plane diffusivities using different levels of analytic closure have been compared with diffusivities obtained from the simulations. © 2003 American Institute of Physics.
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61.20.-p Structure of liquids
66.10.C- Diffusion and thermal diffusion

Density inhomogeneities and electron mobility in supercritical xenon

Richard A. Holroyd, Kengo Itoh, and Masaru Nishikawa

J. Chem. Phys. 118, 706 (2003); http://dx.doi.org/10.1063/1.1527944 (5 pages) | Cited 4 times

Online Publication Date: 20 December 2002

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The low-field mobility of electrons in supercritical Xe has been measured isothermally as a function of density above the critical temperature (289.7 K). At 293 K the mobility varies from a high of 890 cm2/V s at 9.2×1021 atoms/cm3 to a minimum value of 4.6 cm2/V s at a density of 3.5×1021 atoms/cm3, which is just below the critical density. The density dependence of the mobility is reasonably well predicted by the deformation potential model if the adiabatic compressibility is used to characterize the electron–medium interactions. Approximate agreement indicates that electrons are quasifree in supercritical xenon. © 2003 American Institute of Physics.
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72.90.+y Other topics in electronic transport in condensed matter (restricted to new topics in section 72)
51.50.+v Electrical properties (ionization, breakdown, electron and ion mobility, etc.)
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