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15 May 1980

Volume 72, Issue 10, pp. 5291-5790

Page 1 of 3 Pages Next Page | Jump to Page

Study of the corrosion of aluminum by CCl4 using inelastic electron tunneling spectroscopy

R. M. Ellialtioglu, H. W. White, L. M. Godwin, and T. Wolfram

J. Chem. Phys. 72, 5291 (1980); http://dx.doi.org/10.1063/1.439019 (6 pages) | Cited 8 times

Online Publication Date: 15 July 2008

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Inelastic electron tunneling spectroscopy (IETS) has been used to determine the molecular species which occur on an aluminum oxide surface during metallic corrosion by carbon tetrachloride. IETS spectra were obtained for CCl4 adsorbed on aluminum oxide and the observed vibration modes were assigned by comparison with infrared and Raman frequencies. Modes were observed which could be associated with the molecular species CCl4, AlCl, AlCl2, AlCl3, ⋅CCl3, C2Cl6, and the complex CCl+3[AlCl4]−. These species are those in the reaction sequence proposed by Stern and Uhlig for the corrosion of aluminum by CCl4. The results do not provide information on whether the reaction is chemical or electrochemical in nature. The fact that no modes were observed which would reflect oxygen–carbon bonding, and the presence of a large number of aluminum–chlorine modes suggest that the corrosion mechanism is by reaction of the solvent with exposed aluminum atoms.
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81.05.Bx Metals, semimetals, and alloys
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Initial vibrational state dependence of resonant excitation and ‘‘dissociative attachment’’ in electron–N2 scattering

A. Huetz, F. Gresteau, R. I. Hall, and J. Mazeau

J. Chem. Phys. 72, 5297 (1980); http://dx.doi.org/10.1063/1.439020 (8 pages) | Cited 9 times

Online Publication Date: 15 July 2008

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See Also: Erratum

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A beam of vibrationally excited ground state nitrogen molecules has been generated using a microwave discharge. The effect of this vibrational energy on the different decay processes of the A 2Πu state of N−2 formed by electron impact in the 7–13 eV region has been studied using an electron‐impact spectrometer. Firstly, the ’’boomerang’’ oscillations occuring in the excitation cross section of the A 3Σ+u levels increase in amplitude when the initial level is v=1. This effect, as well as the measured cross sections are well described by calculations using the local complex potential model. Secondly, the cross section ratio for the ’’dissociative attachment’’, process yielding unstable N−(3P) from the v=0 and 1 levels has been evaluated indicating that the vibrational energy has almost no effect. The calculations further indicate that this ratio only rises to 4 when going from v=0 to 4 which is in sharp contrast to H2 where, in the 4 eV region the same amount of vibrational energy increases the dissociative attachment cross section by a factor of 360.
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34.80.Gs Molecular excitation and ionization

Determination of frequency shifts by Raman difference spectroscopy

Jaan Laane and Wolfgang Kiefer

J. Chem. Phys. 72, 5305 (1980); http://dx.doi.org/10.1063/1.439021 (7 pages) | Cited 19 times

Online Publication Date: 15 July 2008

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The characteristics of the Raman difference spectra which result when one Raman signal arising from a particular chemical species is subtracted from a second Raman signal due to the same species in a different system, have been examined for both Lorentzian and Gaussian band profiles. The mathematical relationships between δ (frequency separation in the difference spectra), d (intensity of difference spectra), Δ (frequency separation between the two Raman spectra), I0 (Raman band height), and Γ (Raman bandwidth) have been derived. The relationship between the ratios d/I0 and Δ/Γ is most useful for the determination of very accurate values of Δ, the frequency shift. These can often be determined to within ±0.01 cm−1.
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82.80.Dx Analytical methods involving electronic spectroscopy
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods

Calculation of molecular polarizabilities using an anisotropic atom point dipole interaction model which includes the effect of electron repulsion

Robert R. Birge

J. Chem. Phys. 72, 5312 (1980); http://dx.doi.org/10.1063/1.439022 (8 pages) | Cited 49 times

Online Publication Date: 15 July 2008

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The point dipole interaction model for molecular polarizability recently proposed by Applequist, Carl, and Fung is modified by replacing isotropic atomic point dipoles with anisotropic atomic point dipoles. The modified formalism, which is invariant to coordinate transformations, requires an additional empirical parameter for each atom type (ξA, the atomic anisotropy constant) and a single, global parameter applicable to all nonconjugated systems (κ, the repulsion exponent). The atomic polarizability tensor in the molecular environment is evaluated as a function of interatomic electron repulsion. This latter quantity is shown to be related to the degree to which bonding diminishes the polarizability of an atomic center in the direction (s) of the covalent bond (s). The anisotropic atom point dipole interaction model generates identical mean molecular polarizabilities as in the isotropic procedures of Applequist et al., while reducing the average error in the calculated molecular polarizability components to ∼7%. This error is comparable to experimental uncertainty.
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31.15.-p Calculations and mathematical techniques in atomic and molecular physics

Theoretical studies of energy transfer in disordered condensed media

A. Blumen, J. Klafter, and R. Silbey

J. Chem. Phys. 72, 5320 (1980); http://dx.doi.org/10.1063/1.439023 (13 pages) | Cited 62 times

Online Publication Date: 15 July 2008

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In this paper we consider energy transfer among impurity molecules in disordered systems. We use the result of Gochanour, Andersen, and Fayer [J. Chem. Phys. 70, 4254 (1979)] for the generalized diffusion coefficient D(t) in terms of the decay function Φ(t), in conjunction with separate calculations of Φ(t) in the pair approximation to compute D(t). Both multipolar and exchange interactions and both short and long time limits are considered. Comparisons to earlier work are made.
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66.30.J- Diffusion of impurities
66.10.C- Diffusion and thermal diffusion

Time‐correlation functions for restricted rotational diffusion

C. C. Wang and R. Pecora

J. Chem. Phys. 72, 5333 (1980); http://dx.doi.org/10.1063/1.439024 (8 pages) | Cited 79 times

Online Publication Date: 15 July 2008

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The dynamical model of rotational diffusion of rod‐shaped molecules in a conical volume is applied to the calculation of time autocorrelation functions of 1st and 2nd order spherical harmonic functions of the rod’s orientation angles. Numerical results are obtained for the various correlation functions as a function of the polar angle ϑ0 within which the molecule’s axis is confined. Applications to dielectric relaxation, dynamic light scattering, and fluorescence depolarization experiments are pointed out.
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51.10.+y Kinetic and transport theory of gases
51.20.+d Viscosity, diffusion, and thermal conductivity
31.70.Hq Time-dependent phenomena: excitation and relaxation processes, and reaction rates

GaSe Faraday rotation near the absorption edge

A. Balbin Villaverde and D. A. Donatti

J. Chem. Phys. 72, 5341 (1980); http://dx.doi.org/10.1063/1.439025 (2 pages) | Cited 4 times

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We measured the optical dispersion of the interband Faraday rotation of GaSe near the absorption edge at the temperature of 298 °K. From our data it is possible to confirm that a direct allowed electronic transition takes place between the valence and the conduction bands in GaSe.
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78.20.Ls Magneto-optical effects

Absorption spectra of heavily Cu+‐doped KCl, SrCl2 and KI crystals

Taiju Tsuboi

J. Chem. Phys. 72, 5343 (1980); http://dx.doi.org/10.1063/1.439026 (5 pages) | Cited 18 times

Online Publication Date: 15 July 2008

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Optical absorption and magnetic circular dichroism spectra have been investigated in heavily Cu+‐doped KCl, SrCl2, and KI crystals (the concentration is more than 0.1 mole%). In KCl, CuCl microcrystal is formed in the annealed crystals and gives rise to two sharp bands in the 350–380 nm region, which are attributable to the Z1,2 and Z3 exciton bands in the microcrystal by analogy with the Z1,2 and Z3 exciton bands of pure CuCl crystal. The two bands of the microcrystal shift toward lower energy and approach to the pure CuCl exciton band spectrum with increasing microcrystal size. Similar microcrystal has been suggested to be formed in CuCl‐doped SrCl2, and CuI microcrystal in CuI‐doped KI.
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78.30.Hv Other nonmetallic inorganics
78.40.Ha Other nonmetallic inorganics

Molecular dynamics simulation of the plastic phase of solid methane

David G. Bounds, Michael L. Klein, and G. N. Patey

J. Chem. Phys. 72, 5348 (1980); http://dx.doi.org/10.1063/1.439027 (9 pages) | Cited 30 times

Online Publication Date: 15 July 2008

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A molecular dynamics (MD) calculation has been carried out for a model of solid methane at a state condition close to the triple point. We have used systems of 32 and 108 molecules interacting via atom–atom potentials. Equilibrium properties such as the configurational energy, pressure, and specific heat have been evaluated and compared where possible with experimental data. The simulated static structure factor has been analyzed assuming that rotational and translational motion can be decoupled and that the rotational structure factor can be developed as a power series in Kubic harmonics. This description is shown to yield a reasonably faithful representation of the structure in the plastic phase. The dynamical structure factor S(Q,ω) has been calculated for selected values of the momentum transfer hQ. These results have been used to estimate the velocity of sound and hence the elastic constants. The overall agreement of the dynamical properties with experiment is not particularly good, indicating the need for a more refined intermolecular potential.
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61.66.Hq Organic compounds
61.05.F- Neutron diffraction and scattering
62.20.D- Elasticity

Extensions of the LSD approximation in density functional calculations

O. Gunnarsson and R. O. Jones

J. Chem. Phys. 72, 5357 (1980); http://dx.doi.org/10.1063/1.439028 (6 pages) | Cited 50 times

Online Publication Date: 15 July 2008

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Multiplet splittings of first row and iron series atoms and ions have been calculated using two modifications of the local spin density (LSD) functional approach. (a) The energies of individual states are related to linear combinations of energies calculated from single determinants. (b) The spin dependent part of the functional is constructed to reflect the symmetry between electrons and holes. Agreement with experiment is improved significantly and trends are described remarkably well. There is a general tendency for the LSD approximation to overestimate the relative stability of states with greater p‐ and d‐character and singlet–triplet splittings for sd‐configurations.
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31.15.V- Electron correlation calculations for atoms, ions and molecules

Approximating the master equation by Fokker–Planck‐type equations for single‐variable chemical systems

Daniel T. Gillespie

J. Chem. Phys. 72, 5363 (1980); http://dx.doi.org/10.1063/1.439029 (8 pages) | Cited 3 times

Online Publication Date: 15 July 2008

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The stochastic evolution of a well stirred chemically reacting system containing a single time‐varying species X is accurately described by the master equation, in which the total number x of X molecules is an integer variable. We investigate here the legitimacy of approximating the master equation by a Fokker–Planck type partial differential equation in which x is treated as a real variable. Taking the position that any partial differential equation may be regarded as a legitimate approximation to the master equation if and only if it reduces to the master equation when subjected to a proper discretization procedure, we deduce the following: For the special case in which the various chemical reactions can alter the X molecule population by no more than one molecule at a time, a second order (two term) Fokker–Planck equation suffices. However, for the more general case in which reactions are allowed that alter the X molecule population by two molecules at a time, it is necessary to use at least a fourth order (four term) Fokker–Planck equation. In all cases it is assumed that x is large compared to unity; however, no assumptions are made about the way in which the transition probability rates and the molecular population fluctuations scale with the size of the system.
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82.20.Fd Collision theories; trajectory models

Perturbation theory for the free energy of two‐center‐Lennard‐Jones liquids

Johann Fischer

J. Chem. Phys. 72, 5371 (1980); http://dx.doi.org/10.1063/1.439011 (7 pages) | Cited 96 times

Online Publication Date: 15 July 2008

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Recently a perturbation theory for molecular liquids using hard dumbbells as reference system was suggested by Kohler et al. Here, with a somewhat modified approach, it is shown that this type of perturbation theory yields a nearly accurate equation of state even for the most anisotropic two‐center‐Lennard‐Jones molecules, for which simulation results have been reported. In addition to that, an investigation of the different approximations in this approach is given.
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61.25.Em Molecular liquids
64.30.-t Equations of state of specific substances

The electronic spectrum of TiN

A. E. Douglas and P. M. Veillette

J. Chem. Phys. 72, 5378 (1980); http://dx.doi.org/10.1063/1.439030 (3 pages) | Cited 15 times

Online Publication Date: 15 July 2008

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The electronic spectrum of TiN has been observed in absorption for the first time and has been photographed at high dispersion. From the rotational analysis of a number of bands, new constants have been determined for the X 2Σ, A 2Π and B 2Σ states. The vibrational frequency of the ground state determined from the new measurements disagrees with a previously published value.
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33.20.Sn Rotational analysis

Measurement of the rate coefficients for the bimolecular and termolecular ion–molecule reactions of Ne2+ with selected atomic and molecular species

C. B. Collins and F. W. Lee

J. Chem. Phys. 72, 5381 (1980); http://dx.doi.org/10.1063/1.439031 (9 pages) | Cited 19 times

Online Publication Date: 15 July 2008

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This work reports the measurement of second and third order ion–molecule reactions of diatomic neon ions with eight reactants selected because of their widely varying values of polarizability and dipole moment. In this study Ne2+ destruction frequencies have been experimentally determined from measurements of the selectively excited fluorescence of N2+ in high pressure afterglows of mixed gases excited by intense electron beam discharges. Data have been obtained as functions of neon pressure over the range from 500 to 1500 Torr and as functions of the partial pressure of reactant from 100 to 900 mTorr. From this data pressure dependent rate coefficients have been extracted and subsequently resolved into contributions from second order, bimolecular, and third order, termolecular, components. The bimolecular components have been found to agree with tabulated values appearing in the literature. The sensitivity of the method has been sufficient to detect termolecular components as small as 2×10−30 cm6 sec−1 and values were found to range from 3.5×10−30 cm6 sec−1 for Ar to 10−28 cm6 sec−1 for HBr. A classical approximation to the three‐body capture rate has been evaluated which explains these values in terms of the rates at which third body encounters change glancing collisions into inwardly spiraling orbits. The data reported here are in agreement with this model and indicate that the reaction probabilities in this channel are generally high. The sizes of these termolecular rates suggest their general importance in charge transfer reactions in plasmas at atmospheric pressures.
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82.20.Pm Rate constants, reaction cross sections, and activation energies
82.30.Fi Ion-molecule, ion-ion, and charge-transfer reactions
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.80.Hc Glow; corona

On the vibrational structure in the luminescence spectra of uranium‐activated sodium fluoride crystals

K. C. Bleijenberg and P. A. Breddels

J. Chem. Phys. 72, 5390 (1980); http://dx.doi.org/10.1063/1.439032 (9 pages) | Cited 5 times

Online Publication Date: 15 July 2008

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In this paper we report on the luminescence properties of three selectively excited uranate centers in sodium fluoride crystals, viz. the (UO6⋅VF)×, (UO6⋅VF)×p and (UO5F)× centers. The emission transition is assigned to a 4γ7u→12γ8u transition. The emission spectra and the lowest energy band in the excitation spectrum show vibronic patterns associated with two electronic origins due to splitting of the excited electronic states under C4v symmetry. The relative intensities of the two vibronic patterns are temperature dependent. The temperature dependence of the decay time of the luminescence of the three uranate centers provides information about the transitions involved in the luminescence processes. An analysis of the vibrational structure in the luminescence spectra is presented.
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61.72.jn Color centers
78.55.Fv Solid alkali halides
78.40.Fy Semiconductors

Electron correlation, isoelectronic, isonuclear, spin, and excitation aspects of Politzer–Parr partitioning

Russell J. Boyd and George E. Markus

J. Chem. Phys. 72, 5399 (1980); http://dx.doi.org/10.1063/1.439033 (6 pages)

Online Publication Date: 15 July 2008

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The effect of electron correlation on the Politzer–Parr procedure for partitioning the electron density of an atom into core and valence regions is investigated by use of configuration interaction (CI) wave functions. Although the effect is generally small, substantial qualitative differences are observed between the 3, 4, and 6 electron cases. Analytical Hartree–Fock (HF) wave functions are used to reveal the trends in isoelectronic and isonuclear sequences. Correlated wave functions, which explicitly include the interelectronic distance, are used to study the effect of spin and electronic excitation on the populations and dimensions of the core and valence regions in the 1sns excited states of He.
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31.15.V- Electron correlation calculations for atoms, ions and molecules
31.50.Df Potential energy surfaces for excited electronic states

The photolytic cage effect of iodine in the gas phase

J. M. Zellweger and H. van den Bergh

J. Chem. Phys. 72, 5405 (1980); http://dx.doi.org/10.1063/1.439034 (7 pages) | Cited 14 times

Online Publication Date: 15 July 2008

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The laser flash photolysis of iodine has been studied over a wide pressure range in several bath gases. At low pressures the observed quantum yield for photolysis at 6943 Å is independent of the gas density, whereas at higher pressures the quantum yield decreases with increasing gas density. This phenomenon is discussed in terms of the cage effect, and the measured yields are compared with model calculations. The experiments also provide information on the second order rate constants for iodine atom combination.
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82.50.-m Photochemistry
82.20.Pm Rate constants, reaction cross sections, and activation energies

Mössbauer effect investigations on frozen solutions of 129I2 in para‐ and ortho‐xylene

C. I. Wynter, Y. W. Chow, and Ambuj Mukerji

J. Chem. Phys. 72, 5412 (1980); http://dx.doi.org/10.1063/1.439035 (3 pages)

Online Publication Date: 15 July 2008

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The Mössbauer effect in 129I due to the 27.75 keV gamma The Mössbauer effect in 129I due to the 27.75 eV gamma transition was used to investigate the frozen solutions of I2 in para‐ and ortho‐xylene at 20 K temperature. In p‐xylene the electric quadrupole constant and isomer shift were found to be e2qQ/h=−2360±20 MHz and δ=0.922±0.002 mm/s, respectively. A nonzero value of the asymmetry parameter η=0.18 was also obtained. In ortho‐xylene–I2 complex two sets of octet of Mössbauer lines were observed. The values of e2qQ, δ, and η for the two sites of iodine were found to be quite different. The electronic structure of the I2‐organic solvent complexes has been discussed in the light of the charge transfer theory.
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33.45.+x Mössbauer spectra

Isotope, electric field, and vibrational state dependence of single rotational level lifetimes of S1 formaldehyde

James C. Weisshaar and C. Bradley Moore

J. Chem. Phys. 72, 5415 (1980); http://dx.doi.org/10.1063/1.439036 (11 pages) | Cited 42 times

Online Publication Date: 15 July 2008

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Additional single rovibronic level lifetimes of S1 H2CO and D2CO have been measured under collisionless conditions. The H2CO 41 lifetimes vary at least a factor of 150, from 20 nsec to 3.10 μsec. The observed D2CO 41 lifetimes fluctuate about ±20% around a mean value of 6.2 μsec, which is probably close to the pure radiative lifetime. In contrast, the observed D2CO 43 lifetimes vary from 1.09 to 2.46 μsec and the 2143 lifetimes vary from 212 nsec to 1.61 μsec. The onset of rotational state lifetime fluctuations in D2CO thus coincides with the high pressure D2+CO photochemical threshold. All of these results are explained in terms of a collisionless sequential decay mechanism, S1→S0→H2(D2)+CO. The last step probably involves tunneling through a barrier for the lower energies studied. For several H2CO 41 rotational levels application of a uniform external electric field of 0–4.6 kV/cm can change the fluorescence lifetime by at least a factor of 4. This result is understood in terms of small (≲0.05 cm−1) shifts in S1−S0 energy spacings. Quantitative estimates of S1−S0 intramolecular couplings, S0 widths due to dissociation, and S0 level spacings are derived in favorable cases.
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33.70.Fd Absolute and relative line and band intensities
33.20.Wr Vibronic, rovibronic, and rotation-electron-spin interactions
33.20.Sn Rotational analysis
33.55.+b Optical activity and dichroism
33.57.+c Magneto-optical and electro-optical spectra and effects

Vibrational product state distributions of ion–molecule reactions by infrared chemiluminescence: Cl−+HBr,HI→HCl(v)+Br−,I−

Timothy S. Zwier, Veronica M. Bierbaum, G. Barney Ellison, and Stephen R. Leone

J. Chem. Phys. 72, 5426 (1980); http://dx.doi.org/10.1063/1.439037 (11 pages) | Cited 22 times

Online Publication Date: 15 July 2008

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Initial vibrational product distributions have been obtained for the thermal proton abstraction reactions, Cl−+HBr→HCl(v=0,1)+Br− and Cl−+HI→HCl(v=0,1,2)+I−. The experimental method utilizes detection of infrared chemiluminescence from the products of the ion–molecule reactions in a flowing afterglow. A detailed description of the apparatus design and characteristics is given. The initial relative HCl product vibrational distribution for the reaction Cl−+HI was determined to be Nv=1=1.0, Nv=2=0.85±0.05. The ratio of the total emission from Cl−+HBr to that from Cl−+HI was measured to be 39±2%. The results suggest substantial disposal of energy into product vibrations in these ion–molecule reactions.
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82.30.Fi Ion-molecule, ion-ion, and charge-transfer reactions
82.80.Dx Analytical methods involving electronic spectroscopy
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods

Theoretical prediction of the potential curves for the lowest‐lying states of the isovalent diatomics CN+, Si2, SiC, CP+, and SiN+ using the ab initio MRD‐CI method

Pablo J. Bruna, Sigrid D. Peyerimhoff, and Robert J. Buenker

J. Chem. Phys. 72, 5437 (1980); http://dx.doi.org/10.1063/1.439012 (9 pages) | Cited 84 times

Online Publication Date: 15 July 2008

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Large‐scale CI calculations are reported for the potential curves of the isovalent series of diatomic systems CN+, Si2, SiC, CP+, and SiN+ in their lowest electronic states. The standard AO basis sets employed are of double zeta plus polarization quality and the CI method used is of the multireference double‐excitation (MRD‐CI) variety including individualized configuration selection and energy extrapolation. By including up to 17 reference species to generate the MRD‐CI spaces (of orders up to 150 000) and by supplementing the AO basis with f functions it is found that the ground state of CN+ is the π4 1Σ+ species (as in isovalent C2) falling 0.1 eV below the σπ3 3Π state. This result is in significant disagreement with earlier theoretical predictions on this point, which have generally tended to place the 3Π state at least 0.3 eV below 1Σ+. The importance of using more than a single reference configuration in the CI calculations is underscored in this example. For Si2 a similar nearly isoenergetic relationship is noted for its lowest two electronic states, but in this case the competing states are 3Πu and 3Σg−, with 1Σg+ found to lie 0.7 eV higher in this spectrum. The mixed first‐ and second‐row systems SiC and CP+ both show a clear 3Π ground state, well separated from both 1Σ+ and 3Σ−, but in SiN+ the absolute energy minimum is found to occur for 3Σ−, whereby the wide variations in the relative stabilities of all these states from one system to another is seen to be a consequence of the weakening of π bonding relative to σ as second‐row atomic character is introduced into these molecules. Finally generally good agreement is observed between calculation and experiment in this study, with errors of 0.02 bohr and 70 cm−1 being indicated for known bond lengths and stretching frequencies.
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34.20.-b Interatomic and intermolecular potentials and forces, potential energy surfaces for collisions
82.20.Kh Potential energy surfaces for chemical reactions
31.15.V- Electron correlation calculations for atoms, ions and molecules

Molecular beam experiments on the sticking and accommodation of molecular hydrogen on a low‐temperature substrate

T. R. Govers, L. Mattera, and G. Scoles

J. Chem. Phys. 72, 5446 (1980); http://dx.doi.org/10.1063/1.439013 (10 pages) | Cited 32 times

Online Publication Date: 15 July 2008

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Molecular beams, microcalorimetry, and mass spectrometry are used to study the physisorption kinetics of H2 and D2 molecules on a low temperature substrate. The energy transferred to the surface of a liquid‐helium cooled bolometer by an incident room temperature beam of H2 and D2, and the number density of the scattered molecules are measured. The sticking coefficient S and the accommodation coefficient α are obtained as a function of N, the surface coverage by H2 or D2. For both isotopes, S and α depend strongly on N. S(H2) changes from 0.07±0.05 to 0.80±0.02 and α(H2) from 0.31±0.07 to 0.97±0.01 as N increases from ?0 to 3×1015 molecule cm−2. In the same coverage range, S(D2) changes from 0.25±0.05 to 0.92±0.04 and α(D2) from 0.3±0.1 to 0.975±0.025.
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68.43.-h Chemisorption/physisorption: adsorbates on surfaces
34.50.Lf Chemical reactions

The Kirkwood instability in a mean field context

W. Klein and N. Grewe

J. Chem. Phys. 72, 5456 (1980); http://dx.doi.org/10.1063/1.439014 (2 pages) | Cited 15 times

Online Publication Date: 15 July 2008

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We demonstrate for systems with pair potentials of the form V(r)=γdϕ(γr) that the Kirkwood instability analysis of the first equation in the BBGKY hierarchy is correct in the limit γ→0. The cancellation of singular behavior, which occurs for models with short range potentials when higher order equations in the BBGKY hierarchy are considered, does not occur in this mean field (γ→0) limit.
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64.70.D- Solid-liquid transitions
64.60.My Metastable phases

Logarithmic terms in the softness expansion of dilute gas transport properties

R. F. Kayser

J. Chem. Phys. 72, 5458 (1980); http://dx.doi.org/10.1063/1.439015 (11 pages) | Cited 2 times

Online Publication Date: 15 July 2008

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We consider the dilute gas coefficients of viscosity and thermal conductivity for the inverse power potential, ϕ(x,r)=ϕ0(σ/r)x−1, and prove that as x→+0 they have the form a0+a1x+a2x2lnx+a3x2+a4x3ln2x +0(x3lnx). We determine the coefficients a0–a4 in closed form and the analysis may be easily adapted to other properties such as the self‐diffusion coefficient. We also show that the logarithmic terms are due to binary collisions for which the distance of closest approach of the particles is greater than the diameter σ and discuss the implications of this for developing a general perturbation theory for transport properties.
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51.10.+y Kinetic and transport theory of gases
51.30.+i Thermodynamic properties, equations of state
51.20.+d Viscosity, diffusion, and thermal conductivity

Collisional deactivation of selectively excited N+2

D. H. Katayama, Terry A. Miller, and V. E. Bondybey

J. Chem. Phys. 72, 5469 (1980); http://dx.doi.org/10.1063/1.439016 (7 pages) | Cited 43 times

Online Publication Date: 15 July 2008

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Individual vibrational levels of the A 2Πu state of the N+2 molecular ion are excited by a tunable dye laser. Detection of an optical–optical double resonance fluorescence signal produced by a second laser demonstrates that the ions originally pumped into the A 2Πu state are rapidly deactivated by collisions with He into high vibrational levels of the ground X 2Σ+g state. Time and wavelength resolved studies show clearly that the population of a given high vibrational level of the X 2Σ+g state returns into lower A 2Πu state levels giving rise, effectively, to vibrational relaxation within the A state. Rate constants and cross sections are derived for these collisional, internal‐conversion processes. In homonuclear N+2, where symmetry considerations prohibit X and A state perturbations, these processes proceed as rapidly as in heteronuclear species where perturbations are known to be present in the free molecule.
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33.50.Dq Fluorescence and phosphorescence spectra
34.50.Ez Rotational and vibrational energy transfer
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