摘要:

The enhancement of electromagnetic processes on metallic surfaces is discussed in view of applications in surface photochemistry and surface analytics. The strongest enhancements are found on substrates that consist of discrete metal particles. A theoretical description for plasmon resonances of such particles is developed, which includes the effects of finite particle size and of dipolar interactions between the particles. Spheroidal particles with dimensions in the range 10–100 nm are found to produce the strongest enhancements; the role of particle interactions in shifting and broadening the plasmon resonances is discussed.

ISSN:0026-8976    

DOI:10.1080/00268978500102131

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Rotationally inelastic collisions of a3σ-state molecule have been treated by both the accurate quantum close-coupling formalism and the coupled-states approximation. Cross sections are reported for the O2+ He collisions at room temperature for the experimental potential surface of Faubelet al.

ISSN:0026-8976    

DOI:10.1080/00268978500102141

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The dynamics of vibrational relaxation in polyatomic van der Waals clusters is investigated theoretically, using as an example a one-dimensional model of I2(Ne)Nwith excited I2vibration. The method employed is classical dynamics simplified by the time-dependent self-consistent-field (TDSCF) approximation. The dependence of the relaxation on cluster size is examined, with calculations forN= 4, 8, 16 and with extrapolation toN→ ∞ representing I2in a solid Ne matrix. Also studied is the variation of the relaxation mechanism with initial vibrational statev, in the rangev= 25–60. The main results are: (i) Relaxation can be interpreted best as affected by collisions between I2and neighbouring Ne atoms. Collective modes do not, in most cases, play a significant role in the relaxation. (ii) The I2centre-of-mass vibration plays a less significant role than the Ne atoms in the redistribution of the released vibrational energy in the cluster. (iii) The initial relaxation rate decreases with cluster size, the lifetime ofv= 28 being τ = 3·6 ps forN= 4 and τ = 51 ps forN= 8. This is due to decreasing frequency of impulsive I2-Ne ‘collisions’ in the larger clusters. (iv) Initial relaxation behaviour and rates for theN= 16 cluster appear converged to those of the corresponding solid matrix. (v) relaxation dynamics switches from weak to strong coupling-type behaviour asvincreases from 35 to 60.

ISSN:0026-8976    

DOI:10.1080/00268978500102151

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A comparative E.S.R. study of the potassium salts of the anion radicals of tetracyanoquinodimethan(TCNQ) and tetrafluorotetracyanoquinodimethan(TCNQF4) in dilute solutions of ether type solvents reveals that both anion radicals are ion paired. Careful measurements of the hyperfine splittings (hfs) as a function of temperature for both anions in solution show that the isotropic hfs are temperature and solvent dependent. Generally, at temperatures below room temperature, both anion radicals in solution display linewidth alternation phenomena which arise from modulation of the nitrogen and fluorine hfs in TCNQ and TCNQF4, respectively. In contrast, the isotropicg-values of both anion radicals in solution are independent of temperature and the solvents used in this study. The experimental evidence, molecular orbital calculations of the charge density distribution in the free anion radicals, calculations of the ion pair association energies for various K+/TCNQ-and K+/TCNQF4structures and comparison of the calculations with experiment have led to the conclusion that the anion radicals of TCNQ and TCNQF4have different ion pair structures in solution. The significance of this observation for the preparation of donor/acceptor complexes from TCNQ and TCNQF4is discussed.

ISSN:0026-8976    

DOI:10.1080/00268978500102161

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The representations of point groups appropriate to spin -1/2 particles are usually determined by considerations of a group of double the order of the point group under consideration, known as the double group. An alternative definition for double groups is given which makes use of the theory of central extensions and presentations of the point groups.

ISSN:0026-8976    

DOI:10.1080/00268978500102171

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Coupled Hartree-Fock theory is used to calculate two and three body dispersion coefficients for in-crystal ions (Li+, Na+, K+, Rb+, Mg2+, Ca2+, F-, Cl-, O2-) subject to both electrostatic and overlap interactions. For anions the reduction of the dispersion coefficients in the crystalline environment parallels the decrease of the static polarizability.

ISSN:0026-8976    

DOI:10.1080/00268978500102181

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The effect of the quasi degenerate ground state of low spin iron(III) ion on the exchange interaction with an orbitally non-degenerate ion, such as copper(II), has been taken into account, using two formally different models which produce the same results when compared with the bilinear exchange spin hamiltonian. It is found that the four levels which originate from the interactions between the two ground Kramers' doublets are not generally grouped in a singlet and a triplet, but in a less regular fashion, due to the quasi degeneration of low spin iron(III). The model has been applied to some systems recently reported as mimicking the cyanide form of oxidized cytochrome oxidase.

ISSN:0026-8976    

DOI:10.1080/00268978500102191

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The potential of mean force is calculated for one ion immersed in a fluid of dipolar hard spheres in the vicinity of a neutral hard wall. The molecular nature of the solvent induces significant deviations from the primitive model result. A pure MSA treatment would only give the potential of mean force associated with the hard sphere fluid. The present theory automatically includes the existence of the image potential.

ISSN:0026-8976    

DOI:10.1080/00268978500102201

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Raman scattering spectra of the cubic and monoclinic phases of tetracyanoethylene in the external-mode region have been investigated as a function of hydrostatic pressure in a diamond-anvil cell. There is evidence of a possible transition from the cubic phase to a new unknown phase at 13 kbar. The intensities of the Raman spectra are found to vanish at high pressures. Calculation of phonon frequencies as a function of pressure has been carried out in both the cubic and monoclinic phases using atom-atom potentials with a semi-rigid molecule model which takes account of both the external vibrations and those internal vibrations up to 300 cm-1. The calculated frequencies and mode-Grüneisen parameters are compared with the experiments, and Zallen's vibrational scaling law has been successfully investigated.

ISSN:0026-8976    

DOI:10.1080/00268978500102211

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The method of Gillan for solving the Ornstein-Zernike equation is applied to the SSOZ equation. Solutions are obtained for complex molecular models which represent CCl4, N2/O2and CO2/ethane liquids. The peculiarities resulting from the extension of Gillan's algorithm for the description of these fluids are discussed.

ISSN:0026-8976    

DOI:10.1080/00268978500102221

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor