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1 Jul 2002

Volume 117, Issue 1, pp. 1-500

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Quantum chemical study of π–π stacking interactions of the bacteriochlorophyll dimer in the photosynthetic reaction center of Rhodobacter sphaeroides

Yanli Wang and Xiche Hu

J. Chem. Phys. 117, 1 (2002); http://dx.doi.org/10.1063/1.1487831 (4 pages) | Cited 21 times

Online Publication Date: 17 June 2002

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Intermolecular π–π stacking interactions of the bacteriochlorophyll dimer in the photosynthetic reaction center of the purple bacterium Rhodobacter sphaeroides were analyzed by the second order Møller–Plesset perturbation method using the modified 6-31G∗(0.25) basis set with diffuse d-polarization by Hobza and co-workers. MP2/6-31G∗(0.25) calculations yield an intermolecular interaction energy of −21.50 kcal/mol for the bacteriochlorophyll dimer. Thus, the attractive nature of the π–π stacking interaction of the bacteriochlorophyll dimer in the photosynthetic reaction center from Rhodobacter sphaeroides is, for the first time, firmly established. © 2002 American Institute of Physics.
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87.15.M- Spectra of biomolecules
87.15.R- Reactions and kinetics
34.20.Gj Intermolecular and atom-molecule potentials and forces
31.15.xp Perturbation theory

Depolarization as a probe for ultrafast reorientation of diatomics in condensed phase: ClF versus I2 in rare gas solids

M. Bargheer, M. Gühr, and N. Schwentner

J. Chem. Phys. 117, 5 (2002); http://dx.doi.org/10.1063/1.1486444 (4 pages) | Cited 13 times

Online Publication Date: 17 June 2002

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Polarization dependent femtosecond pump-probe spectra display characteristic vibrational wave packet dynamics of ClF in Ar (isotropic cage and small fragment size) and I2 in Kr (cylindrical cage and large fragments). The intensity ratio of the signals for pumping with parallel versus crossed polarization with respect to the probe pulse is close to the value 1/3, as expected for full photoselection immediately after excitation. For ClF this ratio depolarizes to unity within τr = 1.2 ps, showing the ultrafast randomization of the orientation of the molecular bond due to fragment scattering off the matrix cage. The direction of the I2 bond is geometrically fixed by the Kr matrix and the ratio remains constant. © 2002 American Institute of Physics.
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33.20.Kf Visible spectra
78.40.Ha Other nonmetallic inorganics
78.47.-p Spectroscopy of solid state dynamics

Structure of the exact wave function. V. Iterative configuration interaction method for molecular systems within finite basis

Hiroshi Nakatsuji and Masahiro Ehara

J. Chem. Phys. 117, 9 (2002); http://dx.doi.org/10.1063/1.1487830 (4 pages) | Cited 23 times

Online Publication Date: 17 June 2002

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The iterative configuration interaction (ICI) method is applied to molecular systems within finite basis using only few (1–3) variables and shown to give the exact results that are identical to the full CI (FCI) ones. Since each iteration step of ICI is variational, the ICI converges monotonically to the exact solution from above. The diagonalization in ICI is so slight as the number of variables is so small, in contrast to the huge number of variables of FCI. We calculated the molecular ground states of various spin-space symmetries using minimal basis and double zeta basis. The number of iterations for convergence was small for minimal basis but moderate for double zeta basis, considering that only 1–3 variables are optimized in each iteration step. © 2002 American Institute of Physics.
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31.15.V- Electron correlation calculations for atoms, ions and molecules
02.60.-x Numerical approximation and analysis
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A second-order, quadratically convergent multiconfigurational self-consistent field polarizable continuum model for equilibrium and nonequilibrium solvation

Roberto Cammi, Luca Frediani, Benedetta Mennucci, Jacopo Tomasi, Kenneth Ruud, and Kurt V. Mikkelsen

J. Chem. Phys. 117, 13 (2002); http://dx.doi.org/10.1063/1.1480871 (14 pages) | Cited 30 times

Online Publication Date: 17 June 2002

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We present a new implementation of the polarizable continuum model (PCM) at the multiconfigurational self-consistent field (MCSCF) level. This new MCSCF-PCM implementation is based on a second-order algorithm for the optimization of the wave function of the solvated molecule. The robust convergence properties of this approach allows for fast convergence of the PCM-MCSCF wave function for large MCSCF expansions as well as for excited states of solvated molecules. Our implementation also enables us to treat nonequilibrium solvation—that is, to treat excited molecular states generated in a fast excitation process such that not all degrees of freedom of the solvent have relaxed. To demonstrate the applicability of the approach we present calculations of solvation effects on 1,3-dipolar systems and on the ground and excited states of methylenecyclopropene. © 2002 American Institute of Physics.
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82.30.Nr Association, addition, insertion, cluster formation
31.15.xr Self-consistent-field methods

Bessel discrete variable representation bases

Robert G. Littlejohn and Matthew Cargo

J. Chem. Phys. 117, 27 (2002); http://dx.doi.org/10.1063/1.1481388 (10 pages) | Cited 16 times

Online Publication Date: 17 June 2002

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Discrete variable representation (DVR) basis sets on the radial half-line, based on Bessel functions, are presented. These are Hankel transforms of the eigenfunctions of the particle in a spherical box in k space, but there is no box or bound on the radial variable r. The grid points extend to infinity on the r axis. The DVR functions are exactly orthonormal and exactly satisfy the interpolation properties usually associated with DVR functions. The exact matrix elements of the kinetic energy are computed, and the use of the Bessel DVR functions in radial eigenvalue problems is illustrated. The phase space or semiclassical interpretation of the Bessel DVR functions is presented, and variations on these functions, corresponding to alternative boundary conditions in k space, are discussed. An interesting feature of Bessel DVR functions is that they are based on a finite basis representation that is continuously infinite.© 2002 American Institute of Physics.
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03.65.Sq Semiclassical theories and applications
02.10.Ud Linear algebra

An Airy discrete variable representation basis

Robert G. Littlejohn and Matthew Cargo

J. Chem. Phys. 117, 37 (2002); http://dx.doi.org/10.1063/1.1481389 (6 pages) | Cited 5 times

Online Publication Date: 17 June 2002

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A new discrete variable representation (DVR) basis is presented, one that is based on Airy functions. That is, the functions of the “finite basis representation” (actually infinite in this case) are energy eigenfunctions in a constant force field. The exact matrix elements of the kinetic energy are computed. The use of the Airy DVR functions in diagonalizing a one-dimensional Hamiltonian is illustrated.© 2002 American Institute of Physics.
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33.20.Tp Vibrational analysis
02.10.Ud Linear algebra

New developments in the polarizable continuum model for quantum mechanical and classical calculations on molecules in solution

Maurizio Cossi, Giovanni Scalmani, Nadia Rega, and Vincenzo Barone

J. Chem. Phys. 117, 43 (2002); http://dx.doi.org/10.1063/1.1480445 (12 pages) | Cited 545 times

Online Publication Date: 17 June 2002

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The polarizable continuum model (PCM), used for the calculation of molecular energies, structures, and properties in liquid solution has been deeply revised, in order to extend its range of applications and to improve its accuracy. The main changes effect the definition of solute cavities, of solvation charges and of the PCM operator added to the molecular Hamiltonian, as well as the calculation of energy gradients, to be used in geometry optimizations. The procedure can be equally applied to quantum mechanical and to classical calculations; as shown also with a number of numerical tests, this PCM formulation is very efficient and reliable. It can also be applied to very large solutes, since all the bottlenecks have been eliminated to obtain a procedure whose time and memory requirements scale linearly with solute size. The present procedure can be used to compute solvent effects at a number of different levels of theory on almost all the chemical systems which can be studied in vacuo. © 2002 American Institute of Physics.
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61.20.-p Structure of liquids

On the oscillator strength sums S(±1) of atoms and ions

Toshikatsu Koga and Hisashi Matsuyama

J. Chem. Phys. 117, 55 (2002); http://dx.doi.org/10.1063/1.1481758 (4 pages) | Cited 1 time

Online Publication Date: 17 June 2002

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Using rigorous relations discovered recently, the Hartree–Fock limit values of the dipole oscillator strength sums S(−1) and S(+1) are obtained for the 102 neutral atoms He through Lr, singly charged 53 cations Li+ through Cs+, and 43 stable anions H− through I− in their experimental ground states. The present results for the ionic species are the first compilation of the sums. For heavy neutral atoms, the literature S(+1) values are found to be insufficiently accurate. © 2002 American Institute of Physics.
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32.70.Cs Oscillator strengths, lifetimes, transition moments
31.15.xr Self-consistent-field methods

Tetrahedrally invariant discrete variable representation basis on the sphere

Matthew Cargo and Robert G. Littlejohn

J. Chem. Phys. 117, 59 (2002); http://dx.doi.org/10.1063/1.1482697 (8 pages) | Cited 7 times

Online Publication Date: 17 June 2002

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This paper explores the difficulties of constructing multidimensional discrete variable representation (DVR) basis sets and the strategies that can be used to overcome them. A parameter count shows that the conditions on a DVR basis set cannot be satisfied on most spaces of wave functions. One-dimensional, orthogonal polynomials are an exception, but the Ylms on the sphere only go 3/4 of the way, in a certain sense, toward supplying enough parameters to satisfy the DVR conditions. It is shown that DVR sets involving rotationally invariant subspaces of wave functions on the sphere (consisting of complete subshells only) exist only for small values of the angular momentum cutoff. However, an exploration of DVR sets invariant under subgroups of the full rotation group leads to the discovery of a 12-point DVR set that is invariant under the tetrahedral group, whose grid points are the vertices of an icosahedron. © 2002 American Institute of Physics.
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31.15.-p Calculations and mathematical techniques in atomic and molecular physics

Variational density matrix functional theory calculations with the lowest-order Yasuda functional

Jerzy Cioslowski and Katarzyna Pernal

J. Chem. Phys. 117, 67 (2002); http://dx.doi.org/10.1063/1.1481384 (5 pages) | Cited 16 times

Online Publication Date: 17 June 2002

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Fully variational density matrix functional theory calculations reveal a critical flaw in the Yasuda functional derived from the contracted Schrödinger equation and the lowest-order cumulant expansions of the reduced density matrices. Although it yields finite energies in conjunction with finite basis sets, it appears to be unbound from below even for one of the simplest two-electron systems, namely, the helium atom at the s limit, once a complete basis set is employed. This observation casts serious doubts upon its practical usefulness in electronic structure calculations. © 2002 American Institute of Physics.
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31.15.E- Density-functional theory
02.30.Xx Calculus of variations
03.65.Ge Solutions of wave equations: bound states

Correlation in time-dependent density-functional theory

Paul Hessler, Neepa T. Maitra, and Kieron Burke

J. Chem. Phys. 117, 72 (2002); http://dx.doi.org/10.1063/1.1479349 (10 pages) | Cited 18 times

Online Publication Date: 17 June 2002

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The exact time-dependent correlation energy in time-dependent density-functional theory is shown to sometimes become positive, which is impossible with most present TDDFT approximations. Both the correlation potential and energy can be strongly nonlocal in time. A new inequality is derived for the time-dependent exchange-correlation energy. The correlation energy appears to scale to a constant function of scaled time in the high-density limit. In the linear response regime, the correlation energy is shown to become purely adiabatic, but the correlation potential is generally nonadiabatic. The usefulness of the virial theorem as a test of numerical accuracy is demonstrated. All results are found or inspired by exact numerical solution of a simple model system (Hooke’s atom), and inversion of the corresponding Kohn–Sham equations. © 2002 American Institute of Physics.
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31.15.E- Density-functional theory
back to top Gas Phase Dynamics and Structure: Spectroscopy, Molecular Interactions, Scattering, and Photochemistry

Theoretical and experimental studies of the structures of 12-, 13-, and 14-atom bimetallic nickel/aluminum clusters

E. F. Rexer, J. Jellinek, E. B. Krissinel, E. K. Parks, and S. J. Riley

J. Chem. Phys. 117, 82 (2002); http://dx.doi.org/10.1063/1.1481386 (13 pages) | Cited 25 times

Online Publication Date: 17 June 2002

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The structures of NinAlp clusters of all compositions with n+p = 12, 13, and 14 are studied both experimentally and theoretically. Experimental reactions of the clusters with N2 are used to determine the number of Ni atoms residing in the cluster surfaces. In agreement with the theoretical predictions, the N2 saturation levels are consistent with clusters having icosahedral and icosahedral-based structures. The various N2 adsorption channels seen in the experiment are explained in terms of the computed composition-dependent patterns of the configurational energies of the different structural forms. © 2002 American Institute of Physics.
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36.40.Mr Spectroscopy and geometrical structure of clusters

Locating the Al atom in Ni14Al–Ni19Al clusters

E. K. Parks, E. F. Rexer, and S. J. Riley

J. Chem. Phys. 117, 95 (2002); http://dx.doi.org/10.1063/1.1481387 (5 pages) | Cited 5 times

Online Publication Date: 17 June 2002

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Reactions of N2 with NinAl clusters, n = 14–19, are used to determine the location of the Al atom within the cluster framework. N2 saturation levels are consistent with cluster structures in which one surface atom of the corresponding Nin+1 cluster is replaced with an Al atom. For n = 14 and 17–19 it is possible to precisely locate the Al atom within the surface. In general, its placement maximizes the number of Ni–Al bonds for a surface Al atom. © 2002 American Institute of Physics.
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36.40.Jn Reactivity of clusters
36.40.Mr Spectroscopy and geometrical structure of clusters

Stereodynamics and control effects in the ultraviolet photolysis of Ar–HBr

R. Prosmiti and A. García-Vela

J. Chem. Phys. 117, 100 (2002); http://dx.doi.org/10.1063/1.1480866 (10 pages) | Cited 9 times

Online Publication Date: 17 June 2002

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The ultraviolet photolysis of the Ar–HBr cluster is studied by means of quasiclassical trajectory simulations. The goal is to investigate the effect of the initial distribution of intracluster orientations on the photolysis process. Cluster photolysis is simulated starting from two different initial states of Ar–HBr(v = 1), namely the ground and the first excited van der Waals states corresponding to the Ar–H–Br and Ar–Br–H isomers, respectively. These two states represent different initial situations for hydrogen dissociation, which in the first case is hindered to a large extent, and in the second case is not. The probability for the fragmentation pathway into H and Ar–Br radical fragments is found to be substantially higher (and therefore the efficiency of the total fragmentation pathway, into H+Ar+Br, is lower) for the cluster initial state where H dissociation is less hindered. The effect of the angular distributions shape of the initial state is also clearly manifested in the state distributions of the different photofragments. It is concluded that selecting the initial state of the cluster on the basis of the shape of its angular distribution provides an efficient means to control the yield of the different fragmentation pathways, and the final states of their corresponding photolysis products. © 2002 American Institute of Physics.
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82.50.Hp Processes caused by visible and UV light
36.40.Jn Reactivity of clusters

The hydration structure of the lithium ion

Hannes H. Loeffler and Bernd M. Rode

J. Chem. Phys. 117, 110 (2002); http://dx.doi.org/10.1063/1.1480875 (8 pages) | Cited 37 times

Online Publication Date: 17 June 2002

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The hydration structure of Li+ has been studied by means of hybrid quantum-mechanical molecular mechanical molecular dynamics simulations at Hartree–Fock and density-functional level of theory. The size of the quantum-mechanical region and the form of the potential function are shown to be of crucial importance for reliable results. Radial distribution functions, coordination number distributions, and various angular distributions have been used to discuss details of the hydration structure, together with bond lengths and bond angles of the water molecules in the first hydration shell. The lithium ion is found to be mainly fourfold coordinated with some smaller amounts of fivefold coordination. The lithium–water cluster exhibits a nearly perfect tetrahedral but still very flexible structure, in which coordinated water molecules are considerably tilted away from planarity. Water molecules in the first hydration shell are shown to be considerably polarized compared to gas-phase structures. © 2002 American Institute of Physics.
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82.30.Nr Association, addition, insertion, cluster formation
31.15.xv Molecular dynamics and other numerical methods
31.15.xr Self-consistent-field methods
34.20.-b Interatomic and intermolecular potentials and forces, potential energy surfaces for collisions
31.15.E- Density-functional theory

Electronic and rotational energy transfer in F(2P1/2)+H2 collisions at ultracold temperatures

Roman Krems and Alexander Dalgarno

J. Chem. Phys. 117, 118 (2002); http://dx.doi.org/10.1063/1.1480004 (6 pages) | Cited 16 times

Online Publication Date: 17 June 2002

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The dynamics of F(2P1/2)+H2 scattering at ultracold temperatures is studied. It is shown that both the rotational and vibrational excitation of H2 molecules decrease substantially the efficiency of spin–orbit relaxation in F+H2 collisions. It is observed that the near-resonant electronic transition leading to rotational excitation of H2(j = 0) is of the same magnitude at high energies as the off-resonant transition in which the rotational angular momentum of H2 is preserved but becomes dominant in ultracold collisions. The zero temperature rate constant for spin-orbit relaxation of F is computed and suggestions are made as to the chemical reactivity of F(2P1/2) atoms at ultracold temperatures. It is found that rotational relaxation of excited H2 molecules is significantly enhanced by electronic transitions in F atoms and the electronic relaxation in F(2P1/2)+H2(j>0) collisions is suppressed by rotational relaxation of H2. © 2002 American Institute of Physics.
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34.50.Ez Rotational and vibrational energy transfer
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions

Dissociation dynamics of gauche and anti conformations of 1-iodopropane ions prepared selectively by vacuum–ultraviolet mass-analyzed threshold ionization spectrometry: Photodissociation at 426 and 355 nm

Sang Tae Park and Myung Soo Kim

J. Chem. Phys. 117, 124 (2002); http://dx.doi.org/10.1063/1.1480006 (8 pages) | Cited 7 times

Online Publication Date: 17 June 2002

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Mass-analyzed threshold ionization with coherent vacuum ultraviolet radiation was used to generate the gauche, or alternatively anti, ion beam of 1-iodopropane ion. Conformation-selective photodissociation of these ion beams was studied at 426 and 355 nm which correspond to excitation to the second and third electronic states appearing in the photoelectron spectrum, respectively, and compared with dissociation in the first excited state reported previously. Conformation-specificity was not observed at 426 and 355 nm unlike the dissociation in the first excited state. Plausible mechanisms for dissociations from the excited electronic states are discussed based on the presence/absence of conformation-specificity, dissociation anisotropy, and kinetic energy release. © 2002 American Institute of Physics.
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33.80.Gj Diffuse spectra; predissociation, photodissociation
82.50.Hp Processes caused by visible and UV light
33.15.Bh General molecular conformation and symmetry; stereochemistry
33.15.Hp Barrier heights (internal rotation, inversion, rotational isomerism, conformational dynamics)
33.80.Eh Autoionization, photoionization, and photodetachment

Guided ion beam studies of the reaction of Nin+ (n = 2–16) with D2: Nickel cluster-deuteride bond energies

Fuyi Liu, Rohana Liyanage, and P. B. Armentrout

J. Chem. Phys. 117, 132 (2002); http://dx.doi.org/10.1063/1.1481855 (10 pages) | Cited 18 times

Online Publication Date: 17 June 2002

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The kinetic-energy dependences of the reactions of Nin+ (n = 2–16) with D2 are studied in a guided ion beam tandem mass spectrometer. The products observed are NinD+ for all clusters and NinD2+ for n = 5–16. Reactions for formation of NinD+ are observed to exhibit thresholds, whereas cross sections for formation of NinD2+ (n = 5–16) exhibit no obvious barriers to reaction. Rate constants of D2 chemisorption on the cationic clusters are compared with results from previous work on neutral nickel clusters. Nin+–D bond energies as a function of cluster size are derived from threshold analysis of the kinetic-energy dependence of the endothermic reactions, and are compared to previously determined metal–metal bond energies, D0(Nin+–Ni). The bond energies of Nin+–D generally increase as the cluster size increases, and parallel those for Nin+–Ni for many clusters. These trends are explained in terms of electronic and geometric structures for the Nin+ clusters. The bond energies of Nin+–D for larger clusters (n ≥ 11) are found to be close to the value for chemsorption of atomic hydrogen on bulk phase nickel. © 2002 American Institute of Physics.
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82.30.Fi Ion-molecule, ion-ion, and charge-transfer reactions
36.40.Jn Reactivity of clusters
34.50.Lf Chemical reactions
33.15.Ry Ionization potentials, electron affinities, molecular core binding energy
82.20.Pm Rate constants, reaction cross sections, and activation energies

High-spin electronic interaction of small lithium and sodium cluster formation in the excited states

Shigeru Hotta, Kentaro Doi, Koichi Nakamura, and Akitomo Tachibana

J. Chem. Phys. 117, 142 (2002); http://dx.doi.org/10.1063/1.1480869 (11 pages) | Cited 9 times

Online Publication Date: 17 June 2002

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We have carried out the MRCI ab initio calculations for small lithium and sodium clusters, and elucidate the interaction between atoms in various high-spin electronic states, in terms of the quantum mechanical energy densities based on the regional density functional theory [Tachibana, J. Chem. Phys. 115, 3497 (2001)]. When the separated two electronic drop regions, where the electronic kinetic-energy density is positive, connect to each other, it is observed that ratios of occupation on configurations change rapidly in the Li2 molecule. These results are considered as one of the evidences that valence electrons can move around both two Li atoms freely in the meaning of classical mechanics. The shape of electronic drop region depends strongly on the electronic state and represents the characteristics of interaction clearly, and the electronic tension density also gives new images of microscopic electronic stresses. Furthermore, we have clarified the most stable structures of Li3 and Li4 for the high-spin electronic state, which are respectively different from the most stable structures for the low-spin electronic state. The stabilization energy due to taking in a Li atom is raised gradually as the number of atoms in Lin cluster increases in the initial stage of cluster propagation. The formation energies of Na2, Na3, and Na4 clusters are much smaller than that of the corresponding lithium clusters. © 2002 American Institute of Physics.
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36.40.Cg Electronic and magnetic properties of clusters
31.15.A- Ab initio calculations
31.15.vq Electron correlation calculations for polyatomic molecules

Photodissociation dynamics of cyclopropane at 157 nm

Chia C. Wang, Yuan T. Lee, Jim J. Lin, Jinian Shu, Ying-Yu Lee, and Xueming Yang

J. Chem. Phys. 117, 153 (2002); http://dx.doi.org/10.1063/1.1481390 (8 pages) | Cited 21 times

Online Publication Date: 17 June 2002

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Photodissociation dynamics of cyclopropane at 157 nm has been investigated using a new molecular beam apparatus based on vacuum ultraviolet ionization by synchrotron radiation. Four distinct dissociation pathways have been observed. The observed channels are the H formation process, the H2 formation process, the CH2+C2H4 formation process, and the CH3+C2H3 formation process. Experimental results indicate that the H atom products are possibly produced via a synchronous, concerted 2H elimination process, while other channels are all binary dissociation processes. Product kinetic energy distribution of each dissociation channel has been determined from simulating the experimental time of flight spectra. Relative branching ratios for all observed dissociation channels were also estimated based on all detected products. © 2002 American Institute of Physics.
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82.50.Hp Processes caused by visible and UV light
82.20.Hf Product distribution

Absolute cross sections for electron impact ionization of NO2

C. Q. Jiao, C. A. DeJoseph, and A. Garscadden

J. Chem. Phys. 117, 161 (2002); http://dx.doi.org/10.1063/1.1480867 (5 pages) | Cited 8 times

Online Publication Date: 17 June 2002

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Absolute partial cross sections for electron impact ionization of nitrogen dioxide (NO2) are determined using Fourier-transform mass spectrometry in the energy range from threshold to 200 eV. Data are presented for the production of the major ionic species, NO2+, NO+, O+, and N+. Ion intensity dependence on the trapping potential is studied for the purpose of probing the kinetic energy of the product ions from the electron impact ionization. O+ and N+ are found to have significant kinetically excited ion populations. The cross-section data are corrected for loss of energetic species from the trap and the results are compared with previous data. © 2002 American Institute of Physics.
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34.80.Gs Molecular excitation and ionization
33.15.Ta Mass spectra

Resonance and reversibility of vibrational relaxation of HF in high temperature Ar bath gas

Roman V. Krems, Alexei A. Buchachenko, Nikola Marković, and Sture Nordholm

J. Chem. Phys. 117, 166 (2002); http://dx.doi.org/10.1063/1.1482373 (6 pages) | Cited 8 times

Online Publication Date: 17 June 2002

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The Boltzmann averaged rate constants for total vibrational relaxation of HF(v = 1) in collisions with Ar are computed in the range of temperatures between 100 and 1500 K. The computed rate constants overestimate the experimental measurements at high temperatures by a large factor. It is concluded that the deviation between theory and experiment cannot be explained by inaccuracy of the PES or dynamical approximations made. It is shown that increasing initial rotational energy enhances a resonant character of the vibrational energy transfer to a great extent. An assumption is made that total vibrational relaxation of HF(v = 1) at high temperatures is determined by competition between vibrational relaxation to a resonant level (v = 0,jres), vibrational excitation from the resonant level, and purely rotational relaxation of HF(v = 0,jres). It is demonstrated that at high temperatures the latter process can be significantly slower than vibrationally inelastic transitions and rotational relaxation of HF(v = 0,jres) may in fact be a rate-limiting stage of vibrational relaxation. © 2002 American Institute of Physics.
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34.50.Ez Rotational and vibrational energy transfer

Time-dependent quantum wave packet study of H+HCN→H2+CN reaction

Wan-Yong Ma, Ke-Li Han, Ming L. Wang, and John Z. H. Zhang

J. Chem. Phys. 117, 172 (2002); http://dx.doi.org/10.1063/1.1481385 (5 pages) | Cited 9 times

Online Publication Date: 17 June 2002

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Time-dependent quantum wavepacket calculations for the H+HCN reaction are carried out on the ab initio potential energy surface of ter Horst et al. [J. Chem. Phys. 105, 558 (1996)]. The dynamics calculations are performed using both the semirigid vibrating rotor target (SVRT) model [J. Chem. Phys. 111, 3929 (1999)] as well as the pseudo atom–diatom model. Total reaction probabilities from the initial ground state of the reagent are calculated for various values of the total angular momentum quantum number J. Reaction cross sections and rate constants are also calculated. The dynamical result from the SVRT calculation is compared with that from a pseudo atom–diatom calculation in which the HCN is treated as a pseudo diatom. Both the SVRT and pseudo atom–diatom calculations involve three degrees of freedom for the H+HCN reaction due to linearity of the HCN molecule at both reactant and transition states. The results from these two calculations are generally close to each other with some difference at high collision energies. The two models for the current system are essentially the same except that the rotational constant used is different. In particular, the SVRT model uses the correct rotational constant for the linear HCN molecule while the pseudo atom–diatom model produces a rotational constant which is much larger than the correct one. © 2002 American Institute of Physics.
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82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
31.15.A- Ab initio calculations
82.20.Kh Potential energy surfaces for chemical reactions
82.20.Pm Rate constants, reaction cross sections, and activation energies

Photoexcitation of LiH2+ from selected initial states: A time-dependent model

M. Satta, E. Bodo, R. Martinazzo, and F. A. Gianturco

J. Chem. Phys. 117, 177 (2002); http://dx.doi.org/10.1063/1.1482695 (10 pages) | Cited 2 times

Online Publication Date: 17 June 2002

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A new quantum time-dependent treatment has been employed to model the photoexcitation of LiH2+ by looking at the process both in a constrained configuration and in the full three-dimensional space. The study has been carried out by monitoring at the end of the process the fragmentation probabilities, the final vibrational distributions of the molecular fragments, and the angular evolution of the wave functions of the complex on the excited electronic surface. The comparison between different initial conditions is able to shed light on the microscopic mechanism of the energy redistribution, with particular reference to the role of the angular coordinate that turns out to provide efficient energy channeling during the evolution. The possibility of extending the method to larger systems is briefly discussed. © 2002 American Institute of Physics.
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33.80.Gj Diffuse spectra; predissociation, photodissociation
82.50.-m Photochemistry
82.20.Nk Classical theories of reactions and/or energy transfer

Perturbation-facilitated optical-optical double resonance spectroscopy of the h0u−(3P1) and H1u(3P1) ion-pair states of I2

Satoshi Motohiro, Shinsuke Nakajima, and Takashi Ishiwata

J. Chem. Phys. 117, 187 (2002); http://dx.doi.org/10.1063/1.1481391 (10 pages) | Cited 7 times

Online Publication Date: 17 June 2002

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Perturbation-facilitated optical-optical double resonance spectroscopy has been applied to study the h0u−(3P1) and H1u(3P1) ion-pair states of I2 correlating with I−(1S)+I+(3P1). The intermediate states used were the g/u parity mixed states found in the B 3∏(0u+)−X 1∑g+ absorption spectrum near the dissociation limit. We identified several B 3∏(0u+) ∼ 3∏(0g−) coupled states by hyperfine interactions for the first time. These states had the 0u+ and 0g− double-faced character and facilitated to combine the X 1∑g+ ground state with the h0u−(3P1) state in the (1+1) photon excitation scheme following the optical selection rules for one-photon transition. We also accessed the H1u(3P1) state through the B 3∏(0u+) ∼ c1g mixed state, and elucidated the heterogeneous coupling between the h0u−(3P1) and H1u(3P1) states. Our analyses covered the region of about 48 200 to 50 300 cm−1, and gave the molecular parameters of the h0u−(3P1) state valid for v = 0–17 and those of the H1u(3P1) state for v = 0–20. The 3∏(0g−) state used as an intermediate state was analyzed through the dispersed h0u−(3P1)−3∏(0g−) emission in conjunction with the Franck–Condon factor calculations, and the principle spectroscopic constants of the 3∏(0g−) state were reported. © 2002 American Institute of Physics.
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33.40.+f Multiple resonances (including double and higher-order resonance processes, such as double nuclear magnetic resonance, electron double resonance, and microwave optical double resonance)
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