bluuebunny/crossref_metadata_2025 huggingface dataset:
Single electrode potentials related to flat-band voltage measurements on EOS and MOS structures
Authors: Bousse Luc
Published: February 2003

The precise definition and meaning of single electrode potentials is discussed. This definition is then used to derive an expression for the flat-band voltage of electrolyte/oxide/silicon (EOS) structures. The same reasoning also produces an expression for the flat-band voltage of MOS capacitors, which includes dipole interaction terms. The difference in flat-band voltage between EOS and MOS structures on the same wafer involves the potential of the reference electrode and the work function of the gate metal. Experiments were performed with aluminum as gate metal, and a saturated calomel reference electrode. In these circumstances, ΔVFB is determined as 0.86±0.03 V. This value can then be used to derive the single electrode potential of the normalized hydrogen electrode. The result is ENHE = 4.74 V, in very good agreement with other recent determinations.
Conductance of alkali metal ions in compressed water at 25 °C
Authors: Nakahara M. , Török T. , Takisawa N. , Osugi J.
Published: February 2003

Limiting molar conductances (λ0) of Li+, K+, Cs+, and Cl− ions in water have been determined at 25 °C as a function of pressure up to 2000 kg cm−2 from the measured conductances (Λ) of LiCl, KCl, and CsCl. In the pressure range investigated, λ0(Li+) increases, λ0(Cs+) decreases, and λ0(K+) and λ0(Cl−) have a maximum at 520 and 1230 kg cm−2, respectively. The drag coefficient (Δζ) subtracted by that due to Stokes’ law for perfect slip (4πηR) is obtained for the alkali metal ions and compared with that predicted by the Hubbard and Onsager (HO) dielectric friction theory over the pressure range. The observed decrease in Δζ with pressure for the small ion Li+ can be explained by the HO theory, but the increase for the large ion Cs+ shows a limitation of the continuum theory. The latter trend suggests that Cs+ ions may possibly pass through larger unoccupied cavities in the open structure of water which is less developed at higher pressures. Δζ for the medium-sized ion K+ is constant, which seems to result from the balance of the dielectric friction and the passing-through-cavities mechanism.
On the coupling of the diffusion mode to Brillouin peaks
Authors: Cohen Claude , Kwon O’Dae
Published: February 2003

Modified Navier–Stokes equations for solutions of Brownian particles are employed to obtain a description of the Brillouin peaks of these systems. For small particles, the results of the phenomenological binary mixture theory are essentially recovered; and for larger particles, the spectrum exhibits similarities to experimental results from polymer solutions.
Calculation of the nuclear spin–spin coupling constants. IV. π-electron contributions
Authors: Fukui H. , Miura K. , Ohta K. , Tsuji T.
Published: February 2003

The nuclear–spin coupling constants and their π-components in butadiene, hexatriene, octatetraene, and butatriene are calculated using the SOS2 method shown in the previous paper [J. Am. Chem. Soc. 103, 3652 (1981)] in order to investigate significance of π-electron transmission. It has been shown that π-electron contributions are predominant to the coupling constants between nuclei separated by three or more chemical bonds in C–C couplings, by four or more bonds in C–H ones, and by six or more bonds in H–H ones. (AIP)
Temperature coefficient of the dipole moment of undiluted poly(4-chlorostyrene), T≳T
g
Authors: Yoshihara M. , Work R. N.
Published: February 2003

Temperature coefficients of the dipole moments of undiluted poly (4−chlorostyrene) are reported. (AIP)
Photodissociation of O3+
Authors: Goss S. P. , Morrison J. D.
Published: February 2003

Photodissociation of O3+ is reported. (AIP)
Experimental determination of the effective contributions of the L+M and K electrons of argon to the Bethe sum rule
Authors: Duguet A. , Lahman-Bennani A. , Rouault M.
Published: February 2003

Energy loss spectra over a large energy loss range have been obtained for Ar using high energy electron impact spectroscopy. The sums of the generalized oscillator strengths for all possible excitation and ionization transitions have been determined separately for the L+M and K shell electrons relative to the Bethe sum rule for the whole atom. The effective number of electrons NK in the K shell of Ar was determined and found to be the same as theoretical predictions and experimental determinations for dipole oscillator strengths. (AIP)
Comment on ‘‘A statistical theory of rate constants in nonergodic systems’’
Authors: De Leon Nelson , Berne B. J.
Published: February 2003

A comment on the statistical theory of rate constants in non-ergodic systems is presented. (AIP)
The infinite-order-sudden method for light–heavy–light reactions: Application to D+HCl→DCl+H
Authors: Clary David C. , Drolshagen Gerhard
Published: February 2003

An infinite-order-sudden (IOS) theory for light-heavy-light reactions is applied to the D+HCl(v = 0, j)→DCl(v′?1, j′)+H reaction. The results are compared with those obtained using a more accurate quantum-dynamical technique, the ESA–CSA method, in which the energy sudden approximation is used for the entrance channel, while the centrifugal sudden approximation is employed for the exit channel. The computations have been performed using LEPS and DIM potential energy surfaces. We obtain good agreement between the IOS and ESA–CSA results, not only for averaged quantities such as rate coefficients, but also for detailed vibrational-rotational reactive cross sections.
Channel specific spectral properties and time delays for bimolecular collisions
Authors: Wardlaw David , Brumer Paul , Osborn T. A.
Published: February 2003

The relationship between the time delay for scattering initiated in a particular state of a specific arrangement channel and densities of states is derived. Both the quantum [Eq. (66)] and classical versions [Eq. (84)] of this ’’channel specific property’’ are obtained. The resultant properties have significant import in understanding the relationship between collisional time delays and properties of the scattering system.
Solution of the coupled equations of inelastic atom–molecule scattering for a single initial state. II. Use of nondiagonal matrix Green functions
Authors: Thomas Lowell D.
Published: February 2003

This paper presents improvements to a previoulsy developed interative method for computing a single column of the coupled channel S matrix. Nondiagonal matrix Green functions are used in the integral equations and a new numerically stable algorithm is introduced for their evaluation. Improvements in covergence and computer time are demonstrated. Test cases of up to 510 coupled equations have been solved. Integral and differential cross sections have been computed for rotational excitations of CO by He at a collision energy of 1822 cm−1. The results are compared with quasiclassical and IOS calculations.
Excited-state potentials in the Na–Hg system: Analysis of rainbow scattering and polarization effects
Authors: Hüwel L. , Maier J. , Pauly H.
Published: February 2003

In the region from 0.7 to 2.9 eV center-of-mass energy the total differential cross section for the scattering of laser excited sodium in its 3 2P3/2 state against ground state mercury has been measured. Characteristic features of this cross section are two well-separated and undisturbed rainbow structures. Assigning these patterns to rainbow scattering from the Σ and Π branch, respectively, of the excited state potential and analyzing the experimental data in the elastic approximation, yields potential parameters for both branches. As available pseudopotentials for the Na–Hg system fail to reproduce our results, a Lennard-Jones 8,6 model was assumed. Then the well depth and equilibrium distance for the Σ and Π potential are extracted as εΣ = 0.264 eV, εΠ = 0.755 eV and RΣ = 3.72 Å, RΠ = 3.46 Å. The observed variation of the rainbow amplitudes with the angle between the field vector of the linearly polarized light and the relative velocity of the collision pair is interpreted on the basis of the elastic approximation in correlation with the initial alignment of the sodium atoms induced by the laser excitation.
Energy dependencies of the reactions of Ar+ with H2, N2, CO, O2, CO2, N2O, and COS
Authors: Dotan I. , Lindinger W.
Published: February 2003

Reactions of Ar+ ions with H2, N2, O2, CO, CO2, N2O, and COS have been meausred in a flow-drift tube at center-of-mass energies of 0.04–2.5 eV. The reactions with H2 and COS are fast and show only small energy dependences. The reaction with N2 is very slow at thermal energies and the rate coefficient increases very fast with increasing energy. The rate coefficients for the reactions with CO2 and N2O decrease with increasing energy over the whole energy range studied. For the reactions with O2 and CO, we find minima of the rate coefficient at 0.4 and 0.8 eV, respectively, followed by a dramatic increase at higher energies.
Kinetic isotope effects in the Mu+H2 and Mu+D2 reactions: Accurate quantum calculations for the collinear reactions and variational transition state theory predictions for one and three dimensions
Authors: Bondi D. K. , Clary D. C. , Connor J. N. L. , Garrett Bruce C. , Truhlar Donald G.
Published: February 2003

We consider three reactions: H+H2→H2+H; Mu+H2→MuH+H; Mu+D2 →MuD+D. We calculate accurate quantum mechanical reaction probabilities and thermal rate coefficients for all three reactions in collinear geometry using the Liu–Siegbahn–Truhlar–Horowitz (LSTH) accurate potential energy surface. These rate coefficients are used to test conventional transition state theory and the improved canonical variational theory with Marcus–Coltrin-path semiclassical adiabatic ground-state transmission coefficients (ICVT/MCPSAG). The ICVT/MCPSAG theory is found to be greatly superior and reasonably reliable. These conclusions are tested for sensitivity to variations in the potential energy surface by repeating the calculations for the less accurate Porter–Karplus surface. The conclusions are unaltered by this. The ICVT/MCPSAG theory and LSTH surface are then employed to predict the rate coefficients for all three reactions in three dimensions.
Two-color resonance photoionization of aromatic molecules in solid argon
Authors: Kelsall Benuel J. , Andrews Lester
Published: February 2003

High pressure mercury arc photolysis of argon matrix samples of biphenyl, naphthalene, and 1-phenyl-1-propyne containing CCl4 for an electron trap produced very strong parent radical cation absorptions. Filtered irradiations show that two-color photoionization is responsible for ion formation in these experiments. In the case of biphenyl and naphthalene, photolysis data show that the relatively long-lived S1 states are the intermediate in the two-color photoionization process, whereas in the case of 1-phenyl-1-propyne, the T1 state contributes to the two-color photoionization process. The observation of two-color photoionization in these experiments suggests that resonant absorption by an excited molecule into ionization is an extremely high cross-section process.
A method for determination of intra- and interparticle structure factors of macroions in solution from small angle neutron scattering
Authors: Bendedouch Dalila , Chen Sow-Hsin , Koehler W. C. , Lin J. S.
Published: February 2003

Macroions in solution have been studied by a variety of physicochemical methods. In particular, small angle neutron scattering (SANS) and light scattering (LS) have been widely used in this domain (e.g., micelles, emulsions, proteins) because of the wealth of information these techniques can provide. We describe here a method by which both single particle and interparticle structure factors [P(Q) and S(Q), respectively] can be extracted from SANS data. P(Q) is given by the SANS data under conditions of low concentration and moderately high ionic strength where interactions between macroions are negligible. For conditions where the interactions are important and in the Q region covered by SANS, S(Q) can be deduced by dividing the intensity distribution by P(Q) obtained previously. If available, the LS data further provides the osmotic compressibilty so that the values of S(Q) at vanishing Q’s can be interpolated.
A radially restricted Thomas–Fermi theory for atoms
Authors: Kemister Gary , Nordholm Sture
Published: February 2003

A new approach to the correction of the inaccuracies of Thomas–Fermi theory as applied to atoms is developed, in which the exact angular part of the energy eigenfunctions are accepted and the statistical treatment restricted to the radial motion. The Langer correction is used to represent the quantum depletion of electron density close to the nucleus. Orbital eigenvalues are assigned by a quantization scheme which produces exact energies for noninteracting electrons. Self-interaction and spin polarization are allowed for. The predicted total energies are correct to about 4% for the first 20 atoms. Ionization energies and electron densities are also discussed.
Electronic structure of small copper clusters. I
Authors: Tatewaki Hiroshi , Miyoshi Eisaku , Nakamura Takashi
Published: February 2003

The electronic structure of small Cu clusters Cun (n = 2–6) is investigated by an all-electron SCF calculation. Basis sets for the calculations are chosen with special care. The calculated atomization energy per atom increases almost linearly with the number of the Cu atoms from Cu4 to Cu6, while the bond energy defined as the atomization energy per bond shows a gradual convergence. The band structure of clusters is closely investigated. The absolute value of the orbital energies for the highest occupied 4s-like orbitals is around 5 eV for Cu4–Cu6, in agreement with the experimental work function (4.65 eV) of the Cu bulk; however the absolute value of the orbital energies for the highest occupied 3d-like orbitals is around 13 eV, which is much larger than the photoelectronic result of 6.75 eV. In this connection, the importance of the reorganization effect in the d electron ionization is emphasized. It is proposed that the orbital energies of the 3d-like orbitals should be shifted by ∼6 eV to compare them with photoelectron spectroscopic data.
Investigation of the electronic structure of ice by high resolution x-ray spectroscopy
Authors: Gilberg E. , Hanus M. J. , Foltz B.
Published: February 2003

Using a new high resolution concave grating grazing incidence spectrometer, we have investigated the oxygen K emission spectra of ice deposits formed near 0 °C and at liquid nitrogen temperature. The spectra, which have not been recorded so far, were excited by the radiation from a high power rotating x-ray anode loaded with 6 kV and 2.5 A. The spectral resolution amounted to 0.25 eV. The spectrum of the crystallized high temperature deposits follows qualitatively the predictions of a band structure calculation carried out by Resca and Resta (Ref.1). The spectrum of amorphous ice, which has been derived from the low temperature ice spectrum, exhibits features strongly resembling the spectrum of free water molecules as well as structures which can be related to the spectrum of crystallized ice. This suggests that amorphous ice contains molecules which are more or less properly bound in the sense of hydrogen bonding as well as quasifree molecules, the hydrogen bonds of which are severely disturbed or broken.
Statistical rate theory of interfacial transport. II. Rate of isothermal bubble evolution in a liquid–gas solution
Authors: Ward C. A. , Rizk M. , Tucker A. S.
Published: February 2003

The statistical rate theory approach is used to derive the expression for the rate of gas absorption by a liquid. This process involves two sequential rates−the rate of transport from the gas to the surface and the rate of transport from the surface to the bulk liquid. According to the statistical rate theory, the rate limiting step is the rate of transport from the surface. After deriving the rate expression for the rate limiting step, it is incorporated in an integral equation approach for predicting the rate of evolution of a bubble evolving isothermally in a liquid–gas solution. This approach accounts for the movement of the bubble boundary in the diffusion problem. Statistical rate theory leads to a complete expression for the rate of gas absorption; thus by comparing the predicted rate of bubble evolution with a set of measurements, one can investigate the validity of the statistical rate theory. This comparison is carried out and the predictions are found to be in close agreement with the experiments throughout the experimental period.
Vibrational energy relaxation of the cyanide ion in aqueous solution
Authors: Heilweil E. J. , Doany F. E. , Moore R. , Hochstrasser R. M.
Published: February 2003

Vibrational energy relaxation (T1) of the CN− ion is reported for NaCN in saturated H2O/D2O and dilute H2O solutions at room temperature. Time domain measurements of the v = 1, 2080 cm−1 vibration shown T1 is on the order of a few picoseconds. The relaxation time increases with dilution and is apparently sensitive to cation (Na+,K+) and local solution structure.
State selected velocity measurements: NO/Ru(001) thermal desorption
Authors: King David S. , Cavanagh Richard R.
Published: February 2003

The tangential velocity distribution of ground state NO (J\ = 9 1/2, Erot = 165 cm−1) thermally desorbed from R (001) under ultrahigh vacuum conditons was measured by laser excited fluorescence Doppler spectroscopy. The measured Doppler profile was Gaussian in nature, characterized by a temperature T∥ = 235±45 K significantly lower than the surface temperature at the desorption peak of 455 K.
ESR of the high-spin (S = 25/2) Mn5 molecule
Authors: Van Zee R. J. , Baumann C. A. , Bhat S. V. , Weltner W.
Published: February 2003

The linewidths of the ESR spectrum of Mn5 in solid krypton at 4°K are studied. (AIP)
Origins of power law behavior in rotationally inelastic collisions
Authors: Brunner Timothy A. , Scott Thomas P. , Pritchard David E.
Published: February 2003

The rotationally inelastic collision rates in non-hydrogenic atom-molecule collisions are described by an angular momentum based power law. A classical calculation of the rotationally inelastic collison rates is presented (based on the power law). (AIP)
Photoelectron spectrum of H2S following multiphoton ionization
Authors: Miller John C. , Compton R. N. , Carney Thomas E. , Baer Tomas
Published: February 2003

The resonance enhanced multiphoton ionization photelectron spectra, REMPI-PES of H2S is presented. The results lead to a reinterpretation of the mass spectral data of Carney and Baer8. (AIP)
A method to include certain infinite order contributions in a multiconfigurational self-consistent field (MCSCF) calculation
Authors: Igawa Akira , Yeager Danny L. , Fukutome Hideo
Published: February 2003

The independent variables of unitary transformation are transformed into two new groups. Using these new variables, we derive an exact MC energy expression. One group of variables is related to the modes of orbital or configurational mixing. These are approximately determined by using first or second order information of an energy hypersurface. The other group is related to the magnitude of orbital or configurational mixing. These are exactly determined, i.e., through infinite order. With this procedure, we can investigate the structure of the energy hypersurface and more safely approach the desired stationary point when far from convergence. We show the results of MCSCF calculations with these infinite order procedures on the ground states of C2 and CO.
A molecular orbital study of the hydration of ions. The role of nonadditive effects in the hydration shells around Mg2+ and Ca2+
Authors: Ortega-Blake I. , Novaro O. , Leś A. , Rybak S.
Published: February 2003

The role of divalent cations in biology, in particular Ca2+ and Mg2+, has led to many studies of the coordination of these ions. The existence of empirical rules serves to characterize these properties, however, a detailed quantum mechanical analysis of the fundamental causes which are responsible for the nature of such properties is lacking. Here, we perform a molecular orbital study of the interactions involved in the hydration scheme of the ions looking particularly into the role of nonadditive effects. Notable differences are found for the cases of Mg2+ and Ca2+.
Second-order propagator calculation of a doublet P Mg shape resonance
Authors: Donnelly Robert A.
Published: February 2003

We report several calculations on the doublet P shape resonance in the Mg atom by use of a second-order, complex-scaled electron propagator. The results agree with experiment within experimental error, and these are attained within quite small basis sets. Rules for construction of the complex scaled self-energy are given. The diagrammatic expansion corresponds to that for a system in a scaled external potential.
Spin-vibronic transition moments and the phases of spin-orbit matrix elements in asymmetric top molecules
Authors: Lattanzi F.
Published: February 2003

Relations between the phases of spin-orbit matrix elements and of the induced spin-vibronic transition moments in asymmetric top molecules are derived on account of transformation properties under time reversal and by inspection of the spin-orbit coupling mechanism. It is shown that the real or imaginary nature of spin-vibronic transition moments induced by coupling about the molecular y axis is opposite to that of transition moments induced by x- or z-axis coupling. Assuming real values for the matrix elements of Sx±iSy, the reduced matrix elements of the spin angular momenta of the single electrons in the ‖SΣ〉 basis are all real if this set transforms under time reversal as Θ‖SΣ〉 = (−1)S−Σ‖S−Σ〉. Special cases reported in the literature are discussed.
Complete active space (CAS) SCF study of the dipole polarizability function for the X 1Σ+ state of LiH
Authors: Roos Björn O. , Sadlej Andrzej J.
Published: February 2003

The CAS SCF method is applied to the calculation of the dipole polarizability function of the X 1Σ+ state of LiH by using the finite-field perturbation approach. The dipole moment function and the potential energy curve are also computed. The vibrational averaging of electric properties has been carried out with different accurate potential energy curves available for the LiH molecule. It has been found that the vibrational contribution to the polarizability components leads to the change of the sign of the polarizability anisotropy between the second and third vibrational state. The dipole polarizability tensor transition matrix elements for some of the lowest energy vibrational transitions have been calculated and can be checked against the Raman intensity data.
Accurate analytic approximations for the rotating Morse oscillator: Energies, wave functions, and matrix elements
Authors: Elsum Ian R. , Gordon Roy G.
Published: February 2003

The assumption that the effective potential for a rotating Morse oscillator always retains a Morse form enables approximate, analytic expressions to be derived for the energy levels, wave functions, and for matrix elements of positive powers of the internuclear separation of a rotating Morse oscillator. Comparison with exact numerical, and with experimental results, shows that the formulas presented are accurate, even for highly excited vibration-rotation states.
Cobalt cyanoaurate: Crystal structure of a component from cobalt-hardened gold electroplating baths
Authors: Abrahams S. C. , Zyontz L. E. , Bernstein J. L.
Published: February 2003

Cobalt cyanoaurate (I) Co[Au(CN)2]2 is a new material derived from cobalt-hardened gold electroplating bath solutions that crystallizes in the hexagonal system with space group P6422 and six formula weights in a unit cell with a = 8.434±0.004 and c = 20.695±0.006 Å at 298 K. The integrated intensities of a full sphere of reciprocal space, within a radius of (sin ϑ)/λ = 0.85 Å−1, were measured using graphite monochromated MoKα with a CAD-4 diffractometer. The resulting total of 12 037 structure factors gave 1969 terms after averaging, of which 717 were accepted as reliably observed. Patterson and Fourier series were used to solve the crystal structure, which was refined by the method of least squares: the final agreement factor R = 0.0358. The atomic thermal vibrations are highly anisotropic. The Au(CN)−2 ion departs slightly but significantly from linearity with a C–Au–C angle of 173.1±1.5° and mean Au–C–N angle of 170.6±1.7°. The cyano groups also form tetrahedral Co(NC)2−4 ions: conversion to the octahedral Co(NC)2−6 ion occurs at high concentrations of K+ in solution. The crystal radius of high-spin Co(II) decreases by 0.15 Å as the coordination changes from octahedral to tetrahedral, for a two-coordinated N radius of 1.245 Å. The mean Au–C distance is 2.003±0.016 Å with C–N = 1.124±0.021 Å and Co–N = 1.973±0.013 Å. The mismatch between Au–Au separations in Co[Au(CN)2]2 and in (111) of elementary Au is less than 8%. The identical but rotated sequence of Au–Au separations at the c/3 and 2c/3 levels in Co[Au(CN)2]2 coincides within 2.4% with the corresponding spacings in the element normal to (111) at the a√3 and 2a√3 levels. These small mismatches could result in epitaxial overgrowth leading to gold hardening and incorporation of the observed impurities in the electrodeposit.
Comments on some reduced descriptions of coherent and incoherent dynamics of multilevel systems
Authors: Gamliel D. , Mukamel S. , Smilansky U. , Gross D. H. E. , Möhring K.
Published: February 2003

We discuss some newly developed reduced equations of motion of systems which undergo transition from coherent to incoherent dynamics, and compare these equations with the well-established Bloch equations. We show that in spite of some structural similarities, there are important differences in the behavior of their solutions.
Neutron diffraction structural study of pyroelectric Ba(NO2)2⋅H2O at 298, 102, and 20 K
Authors: Kvick Å. , Liminga R. , Abrahams S. C.
Published: February 2003

Neutron diffraction studies of barium nitrite monohydrate [Ba(NO2)2⋅H2O] have been made at 20, 102, and 298 K on the same crystal. Intensities of 954 (20 K), 2179 (102 K), and 2393 (298 K) reflections were measured at the Brookhaven National Laboratory high flux beam reactor. The structures were refined on the basis of the hexagonal space group P65 to yield agreement factors R(F2) = 0.028 (20 K), 0.034 (102 K), and 0.061 (298 K). The thermal expansion is nonlinear along both a and c axes, with α1 = 3.8×10−6 K−1, β1 = 2.8×10−8 K−2, α3 = 21.3×10−6 K−1, β3 = 10.9×10−8 K−2. The cell dimensions are a = 7.0524(24) Å, c = 17.6372(80) Å at 20 K, a = 7.0559(23) Å, c = 17.6810(77) Å at 102 K, and a = 7.074 90(3) Å, c = 17.890 87(12) Å at 298 K. The mean-square amplitude of thermal motion of Ba is proportional to temperature in the range 298 to 20 K, with small departures from linearity for the O and N amplitudes and larger departures for the H nuclear amplitudes. The Ba2+ ion is coordinated by nine oxygen atoms and one nitrogen atom at an average distance of 2.881 Å at 20 K, 2.884 Å at 102 K, and 2.902 Å at 298 K. The increase in length corresponds completely to the lattice expansion. A maximum difference within a nitrite ion of 0.015 Å in N–O bond lengths, observed at 298 K, is reduced to 0.008 Å at 20 K for a mean N–O distance of 1.254 Å. One O–H bond of 0.958 Å, which forms a bifurcated hydrogen bond with two oxygen atoms, is identical in length to that in the free water molecule; the other is slightly elongated by formation of a nearly linear hydrogen bond to a nitrogen atom. The largest nuclear displacement between 298 and 20 K in this pyroelectric crystal is only 0.038 Å along the polar axis.
Photoinduced diffusion of trapped electrons
Authors: Funabashi Koichi
Published: February 2003

The wavelength dependence of a photoinduced diffusion coefficient is contrasted with that of the absorption spectrum for trapped (or solvated) electrons in molecular aggregates. The theory is based upon the supposition that the absorption spectrum is the sum of electron-transfer transitions involving different transfer distances. For the same incident photon flux, the diffusion coefficient is shown to peak at a photon energy which is blue shifted from that of the absorption peak.
Multiphoton ionization in the organic condensed phase: A three-photon study of liquid benzene
Authors: Scott Thomas W. , Braun C. L. , Albrecht A. C.
Published: February 2003

The three-photon ionization spectrum of liquid benzene is reported in the 360–440 nm one-photon spectral region. Simultaneous two-photon absorption indirectly populates what appears to be the lowest singlet excimer state in the first step of the ionization sequence. Absorption of a third photon by the excimer then reaches superexcited states of the liquid. The influence of temperature and applied electric field on the overall ion yield can be rationalized if these superexcited levels collapse into geminate charge pairs of ≊25 Å radius. Free charge carriers are finally formed by thermal ionization of geminate pairs with efficiencies on the order of 10−3.
The central Lorentzian in the depolarized Rayleigh spectra of liquid CCl4 and GeCl4
Authors: Stevens J. R. , Patterson G. D. , Carroll P. J. , Alms G. R.
Published: February 2003

The central Lorentzian peak in the depolarized Rayleigh spectrum of CCl4 and GeCl4 is studied as a function of temperature using a high resolution Fabry–Perot interferometer. The results are shown to be consistent with a recent theory by Madden which attributes the depolarized spectrum to scattering by anisotropic pairs of density fluctuations. It is also shown that the ubiquitous presence of long-lived asymmetric vibrationally excited molecules may give rise to a spectrum whose width is determined by the reorientational relaxation time of the molecules. In the molecules studied here, the two relaxation times are comparable.
BCl3 absorption of CO2 laser lines
Authors: Richton R. E. , Farrow L. A.
Published: February 2003

Extinction coefficients for the 0001–1000 band of the CO2 laser as absorbed by BCl3 are reported. The P(8) line is shown to be the most sensitive as a probe. A band model calculation summing ≊200 000 theoretical lines describes the data very well if the upper state inertial constants are fit such that B′ = B\−0.0013 and C′ = C\+0.0005. The band strength is found to be (5.90±0.30)×107 cm/mol, larger than a previous experimental determination but in better agreement with CNDO calculations.
The two-photon absorptivity of rotational transitions in the A 2Σ+(v′ = 0)–X 2Π(v′′ = 0) gamma band of nitric oxide
Authors: Gross K. P. , McKenzie R. L.
Published: February 2003

A predominantly single-mode pulsed dye laser system giving a well-characterized spatial and temporal output suitable for absolute two-photon absorptivity measurements was used to study the NOγ(0,0)S11+R21(J\ = 7-1/2) transition. Using a calibrated induced-fluorescence technique, an absorptivity parameter of 2.8±1.4×10−51 cm6 was obtained. Relative strengths of other rotational transitions in the γ(0,0) band were also measured and shown to compare well with predicted values in all cases except the 012(J\ = 10-1/2) transition.
Experimental and theoretical investigation of self-broadening and self-shifting of ammonia transition lines in the ν2 band
Authors: Baldacchini G. , Marchetti S. , Montelatici V. , Buffa G. , Tarrini O.
Published: February 2003

We have measured self-broadenings and self-shiftings of several rotovibrational transitions of the ν2 band of NH3. We have found smaller broadenings and bigger shifts with respect to the known data of the inversion spectrum in the microwave region. The experimental results are compared with the Anderson original line broadening theory, successively extended in order to calculate the shift also. The agreement between experiments and theory is quite good so that it is possible to select the right procedure among those usually adopted in order to avoid divergences occurring in the Anderson’s perturbative treatment of the molecular collision matrix.
Studies of multichannel rotational predissociation of Ar–H2 van der Waals molecule by the complex-coordinate coupled-channel formalism
Authors: Chu Shih-I , Datta Krishna K.
Published: February 2003

The complex-coordinate coupled-channel (CCCC) formalism previously developed [J. Chem. Phys. 72, 4772 (1980)] is applied to the accurate determination of the level widths (lifetimes) and energies of rotationally predissociating metastable Ar⋅⋅⋅H2 van der Waals molecules. Calculations are performed using several realistic anisotropic potentials obtained recently by experiments, including Lennard-Jones (LJ), Buckingham–Corner (BC) type potentials, as well as the semiempirical potential of Tang–Toennies (TT). New numerical methods are introduced here to deal with the complex rotations of piecewise inhomogeneous potentials such as those of BC and TT. It is found that the CCCC method is capable of providing reliable results for any given potential surface. Furthermore, the CCCC results are sensitive to the potential surfaces used. For example, the linewidths predicted for different LJ potential surfaces considered here vary by a factor as large as 4. However, the agreement among more recent potentials, namely, the BC potential of Zandee and Reuss and that of Le Roy and Carley as well as the potential of Tang and Toennies, is much closer: the resonance energies agree to within 1 cm−1 and the linewidths to within 30%.
A quantum analog to the classical quasiperiodic motion
Authors: Hose Gabriel , Taylor H. S.
Published: February 2003

A quantum mechanical mnemonic which identifies the energy levels corresponding to those obtained by quantization of the classical quasiperiodic motion in coupled anaharmonic oscillator systems is presented. The mnemonic reproduces the known classical regular to irregular behavior as a function of the energy. The mnemonic is based on the definition of a suitable effective Hamiltonian for each level. Quasiperiodic levels are those in which the wave function has a weight greater than 50% on a degenerate subspace of any separable part of the Hamiltonian. This condition ensures that there exists an effective Hamiltonian defined on this degenerate subspace which commutes with the separable Hamiltonian; the latter is therefore an effective constant of motion for the total Hamiltonian. In some cases, depending on the degenerate subspace, other effective constants of motion exist. There is a correlation between the semiclassical quantization methods of quasiperiodic trajectories and the present effective Hamiltonian approach.
Complex coordinate, self-consistent field calculations of vibrational resonance energies
Authors: Christoffel K. M. , Bowman J. M.
Published: February 2003

Application of the complex coordinate rotation method to molecular vibrational resonances is made at the self-consistent field (SCF) level. The highly coupled, two-mode, model system of Waite and Miller [B.A. Waite and W. H. Miller, J. Chem. Phys. 73, 3713 (1980)] is used to test the accuracy of the complex coordinate SCF method. A substantial improvement over the zero-order results is found.
Precise test of the Coulomb-projected Born approximation for the 2 1S and 3 1S excitation of helium by electron impact
Authors: Dillon Michael A. , Inokuti Mitio
Published: February 2003

By use of the accurately known generalized oscillator strength (i.e., the result of the first Born approximation due to Kim and Inokuti), we have evaluated the differential cross sections for the 2 1S and 3 1S excitation of helium by electron impact, much more precisely than before, within the Coulomb-projected Born approximation. The results are in good agreement with measurements by Dillon and Lassettre reported in 1975. The method of the present calculation is based on the Fourier decomposition of the Coulomb potential for interactions between the incident electron and electrons in the target atom, and has been used in a few other contexts. We point out here that the same method can be readily extended to many other scattering approximations such as distorted-wave approximations, either with or without account for electron-exchange effects.
The metastable and collision-induced dissociation of propane, CO2-cluster, and NH3-cluster ions
Authors: Futrell J. H. , Stephan K. , Märk T. D.
Published: February 2003

Metastable decay reactions occurring in the mass spectrum of C3H8 and the cluster species (NH3)2, (NH3)3, and (CO2)2 were investigated by decoupling the acceleration and deflection fields of a reversed Nier–Johnson geometry double-focusing mass spectrometer. It is shown that the present experimental setup (molecular beam-electron impact ion source-deflection optics) permits a clean separation of molecular beam processes from background processes. The general reliability of our instrument is demonstrated by the study of the well-characterized metastable ions in propane, which corrobated and extended previous measurements. Moreover, the ability to differentiate and study quantitatively both collision-induced and unimolecular decay processes with the combined techniques of our instrument is demonstrated. Our tentative conclusion from the present study of ammonia and carbon dioxide clusters is that small cluster ions should be described by a loosely coupled oscillator model. The simple dissociation of (CO2)+2, (NH3)+2, and (NH3)2H+ are collision-induced in the present work, supporting this model. On the other hand, the observation of true (unimolecular decay) metastables for the rearrangement decay of (NH3)+2 to NH+4 and (NH3)3+ to NH+4. NH3, and for the dissociation of (NH3)3H+ to (NH3)2H+, suggests that energy exchange within a statistical ensemble of strongly coupled oscillators controls the decomposition kinetics of these species.
Vibrational relaxation in ozone recombination
Authors: Joens Jeffrey A. , Burkholder James B. , Bair Edward J.
Published: February 2003

The time dependence of different components of the population of vibrationally excited ozone is measured during its formation by recombination, using changes in the shape of the vibronic absorption continuum as a probe. The time dependence of the population of every component of the total population is distinguished as either the ground state P000, states excited only in the bending mode P0x0, or states excited in the stretching mode Pxxx. In addition, two levels of states excited in the stretching mode are distinguished. The results give values for the V→T relaxation of the bending mode k2 that are consistent with the values obtained in other laboratories. For relaxation by O2 in the absence of O3†–O3† mode equilibration, the value obtained for the ratio of the rate constant k12, for V→V transfer from the stretching modes to bend, to k2 is α = 0.4±0.1. Assuming that the newly recombined ozone initially relaxes through a quasicontinuum of levels, for which the rules for energy exchange are not known, it is shown that the observations from which α is derived set limits on the pathway through the quasicontinuum.
Analytic estimation of almost-resonant molecular energy transfer due to multipolar potentials. II. V
V relaxation of the laser levels of CF4
Authors: Pack Russell T
Published: February 2003

A quantal almost-resonant collisional energy transfer theory with a natural cutoff for the Born approximation is extended to spherical-top polyatomic molecules and used to calculate the rate from 100–400 K for the almost-resonant vibration to vibration process which depletes the upper laser level and populates the lower laser level of CF4.
Quantum mechanical calculations of symmetric molecular charge exchange and vibrational excitations in O+2+O2 collisions
Authors: Becker C. H.
Published: February 2003

A scattering formulation is presented for symmetric molecular charge exchange treating the internal vibrational degrees of freedom and translation quantum mechanically. A unitary transformation is found to reduce the 2n coupled radial equations to two sets of n coupled equations. The formulation is applied to O2+(X 2Πg, v)+O2(X 3Σg−, v′) at 1, 8, and 36 eV center-of-mass collision energies. Convergence with respect to vibrational basis set size is found to be slower at lower energy. Integral cross sections and transition probabilities as a function of nuclear orbital angular momentum are presented. The integral cross sections summed over final levels for vibrational excitation and de-excitation and for charge transfer are on the order of 10 Å2. Comparisons of earlier classical path calculations with the present results do not show quantitative agreement at these energies.
A Monte Carlo quasiclassical trajectory study of energy transfer in Ar+HF collisions
Authors: Thompson Donald L.
Published: February 2003

Quasiclassical trajectories on a pairwise-additive potential-energy surface have been used to compute state-to-state cross sections for energy transfer in Ar+HF. Interest is focused upon relaxation from high vibration-rotation states. Pure-rotational energy transfer in excited vibrational states, vibrational relaxation, and the effect of relative translational energy on the energy transfer were also investigated. Most of the calculations were carried out for 1.0 eV relative translational energy. Initial vibrational states vi = 0, 2, 4, and 6 and initial rotational states Ji = 0, 10, 20, 30, and 40 were studied at this collision energy. The energy transfer for initial state vi = 4, Ji = 20 was studied at the initial relative translational energies 0.2, 0.4, 0.6, 0.8, and 1.0 eV. For collisions of Ar with highly excited HF the dominant energy transfer is V-R. The energy transfer results in an increase in the rotational state for downward vibrational transitions and a decrease in rotational state for upward vibrational transitions. The results suggest that pure-rotational energy transfer for low levels of rotational energy (Ji≲10), even in high vibrational states, should be accurately described by the rigid-rotor approximation. None of the energy transfer processes has a strong dependence on the initial relative translation energy, however, the influence is not negligible in all cases.
Vibrational energy transfer from highly excited anharmonic oscillators. Dependence on quantum state and interaction potential
Authors: Nesbitt David J. , Hynes James T.
Published: February 2003

In order to elucidate the general features of vibrational deactivation of highly excited anharmonic oscillators, we present quasiclassical trajectory calculations on prototype collinear I2 (v)-inert gas collision systems. The results for vibrational-translational energy transfer reveal several interesting trends as a function of initial vibrational quantum state, projectile mass, and projectile–oscillator interaction potential. (1) Vibrational deactivation is inefficient from all quantum levels and for all projectile masses. The average energy transfer per collision ΔE is strongly peaked at intermediate vibrational levels (v≊80) and is observed to be at most ≊−kbT. Furthermore, when scaled to h/ω(E), the ’’local’’ oscillator energy spacing, ΔE can be accurately represented by a simple power law in vibrational quantum number over a wide range of bound states. (2) Energy transfer is progressively less efficient from levels in the neighborhood of and approaching dissociation. (3) Vibrational energy loss for high levels of initial vibrational excitation (v≳90) is rather insensitive to the nature of the interaction potential. Smooth exponential and hard-sphere interaction results differ by less than an order of magnitude. This observed insensitivity motivates the development of an analytic collision model, in which simple hard-sphere geometry and dynamics are used to calculate ΔE. The model results are in qualitatively good agreement with trajectory calculations and also indicate that nonuniform sampling of the anharmonic oscillator velocity and phase are responsible for decreased energy transfer efficiency from high vibrational states.
Nonadiabatic coupling between low lying singlet states of geometrically relaxed olefines: Ethylene and propylene
Authors: Persico M. , Bonac̆ić-Koutecký V.
Published: February 2003

Geometrical relaxation in low lying singlet excited states of biradicaloids with equal and different radical centers has been investigated employing ab initio large-scale CI treatments. The nonadiabatic coupling matrix elements between three singlet electronic states through twisting of the olefinic bond in propylene, unpyramidalized ethylene, and ethylene pyramidalized at one or both ends have been determined. The results are analyzed in terms of ionic and covalent contributions to the electronic wave functions. For large twisting angles a crossing between the two lowest excited states occurs for nonpyramidalized and dipyramidalized ethylene. The crossing becomes avoided for systems with two unequal radical centers. In the latter case both excited states exhibit large charge separation of opposite direction. In the region of avoided crossing the nonadiabatic coupling function between two excited states exhibits a peak which goes over into a broad shape curve as the difference in the electronegativity of the two radical centers increases. If the large polarity of the excited states is not localized within a few degrees of the twisting angle, the correction to the Born–Oppenheimer states through nonadiabatic coupling does not substantially change the main features of these states. The nonadiabatic coupling functions between the ground state and each of the two excited states are broad curves symmetrical with respect to the 90° twist. It is concluded that internal conversion from the excited into the ground state is not likely to be extremely fast.
Oxygen K hole photoionization cross section of CO2
Authors: Daasch W. Robert , Davidson Ernest R. , Hazi Andrew U.
Published: February 2003

The oxygen K hole photoionization cross section of CO2 has been computed in the discrete basis improved virtual orbital (IVO) and CI virtual orbital (CIVO) approximations. Reasonable agreement with the experimental result is obtained. Effects of basis set, hole localization, and imaging procedure are examined, and shake-up effects are discussed.
A new gradient expansion of the exchange energy to be used in density functional calculations on atoms
Authors: Bartolotti Libero J.
Published: February 2003

A gradient expansion of the exchange energy density functional for an N electron atom is obtained by imposing the following conditions: (i) The functional scaleslike potential energy. (ii) Nonlocality is introduced through powers of electron position and powers of the gradient of the density. (iii) The atomic cusp condition is exactly satisfied. The resulting functional is K[ρ] = C(N)ℱρ4/3 dτ+D(N)ℱr2ρ−2/3 (∇ρ⋅∇ρ) dτ = ℱρ4/3 [C(N)+D(N) y2] dτ, where y = ∂ ln ρ/∂ ln r. Imposing conditions on the functional and its functional derivative which must be satisfied when evaluated with the exact one-electron density, we obtained the following estimates of the coefficients: C(N) = −(3/4)(π/3)1/3 −(3/4)(π1/3/N2/3)[1−(3/π2)1/3] and D(N) = π1/3/729 N2/3. Evaluating the present functional with 1785 Hartree–Fock densities and comparing the resulting energies to the Hartree–Fock energies gave an average 0.04% error. Solving the Euler–Lagrange equation associated with our functional gave energies which differed from Hartree–Fock energies by about the same percentage error as when the energy density functional was evaluated with Hartree–Fock densities. Unlike the usual gradient expansion, our expansion does not prevent the virial theorem or the atomic cusp condition from being exactly satisfied.