摘要:

The binding of a new stabilizing ligand (monosulfonated triphenylphosphine) to the surface of large, monodisperse gold cluster particles is studied by surface enhanced Raman scattering (SERS). From a detailed assignment of the bands, partial information on the adsorption geometry of the ligand onto the colloid surface is obtained. The SERS enhancement is estimated from the experiment, and compared with the theoretical value calculated for the electromagnetic contribution due to local field enhancement. When a sample of the purple colloidal solution is placed on a glass substrate and the solvent is allowed to evaporate, the solid film takes on the appearance of metallic gold; this colour change is reversed upon re-dissolution of the solid. Reflectance spectra have been recorded to characterize the spectral changes occuring, and are interpreted in terms of the Maxwell-Garnett theory for a composite medium consisting of gold spheres in an aqueous host medium.

ISSN:0026-8976    

DOI:10.1080/00268979100101691

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A study of the density profiles of a hard sphere and a Lennard-Jones fluid confined to spherical pores has been carried out using both computer simulation and a density functional proposed by Rickayzen and Augousti. For hard sphere fluids very good agreement between the results of theory and simulation are obtained. For the Lennard-Jones fluid, there is reasonable agreement between theory and simulation at the highest temperature studied (T= 2·01Tc) but the agreement deteriorates as the temperature of the fluid is reduced.

ISSN:0026-8976    

DOI:10.1080/00268979100101701

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Far-infrared absorption spectra of liquid acetonitrile at temperatures ranging from 238 to 343 K were measured with a source of synchrotron orbital radiation. On the basis of an optical theory, a theoretical expression for transmittance of a cell filled with liquid was obtained as a function of the optical constants of the liquid. Assuming an analytical form with seven parameters for the absorption coefficients, the refractive indices were analytically calculated by the Kramers-Kronig relation. The parameters of the absorption coefficients were adjusted by least-squares fitting of the theoretical transmittance to the observed transmittance. The resulting optical constants at 298 K were in good agreement with the previously reported results by a laser ATR method. The effect of temperature on the band shape of the absorption is remarkable and will provide an important clue to molecular reorientational dynamics. On the other hand, the molecular dipole moments obtained from the integrated intensities are nearly independent of temperature, being 4·5 ± 0·1 D in the 238 to 343 K range.

ISSN:0026-8976    

DOI:10.1080/00268979100101711

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Local structure and reorientational dynamics in liquid acetonitrile, which are related to intensities and band shapes of the far-infrared spectra, were studied by molecular dynamics calculations. The calculations were performed at 233, 291 and 350 K with two types of potential, with and without Coulomb terms involving fractional charges on each atom in addition to the atom-atom Lennard-Jones terms. Comparison of results of the two types of calculations, MD(LJ + FC) and MD(LJ), shows that the dipole-dipole interaction plays an important role in determining the average local structure and the intermolecular cross-correlation of the reorientational motion. The result of MD(LJ + FC) reproduces well both a relative enlargement of the molecular dipole moment in the liquid phase and a characteristic feature of the rotational velocity correlation function.

ISSN:0026-8976    

DOI:10.1080/00268979100101721

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

This paper discusses the implementation of the reaction field method previously developed [1] for inhomogeneous fluids, and presents results for selected properties of a dipolar model fluid at a liquid-gas interface. To implement the reaction field, a fit function based on the image charge approach is introduced. The fit function features eight image charges placed at uniquely determined points inside a dielectric slab of infinite extent in thex, y-plane and fixed height in thez-direction in which the molecular dynamics (MD) simulation sample is embedded. In addition to the image charges, a set of seven scaling parameters is introduced to take care of the effect of truncating the image charge expansion. Based upon this approach, MD runs are performed with and without an applied reaction field. These runs reveal that, similar to what is known for dipolar bulk fluids, purely structural properties remain unaffected while dielectric properties are very sensitive to the reaction field.

ISSN:0026-8976    

DOI:10.1080/00268979100101731

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

We report the first direct gas phase observations of the electronic transitions,2Δ5/2, ν = 0 →2Π3/2, ν = 0 and2Δ5/2, ν = 0 →2Δ3/2, ν = 1, in the NiH radical. From the observed transitions we obtained transition frequencies and electronicgfactors.

ISSN:0026-8976    

DOI:10.1080/00268979100101741

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

We report the first direct observation of the vibration-rotation spectrum of the diatomic chromium-hydride in its X6Σ+ground state by CO-Faraday laser magnetic resonance spectroscopy (LMR). Transitions of all four isotopomers attributed to the fundamental and the first hot band were detected. The spectra were analysed by a single least-squares fit using an effective Hamiltonian. A set of effective molecular parameters for the X6Σ+ground state is given.

ISSN:0026-8976    

DOI:10.1080/00268979100101751

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

We report the first direct observation of the vibration-rotation spectrum of the tin deuteride radical in its electronic ground state2Π by infrared diode laser spectroscopy. The SnD radicals were produced using tetramethylstannane (Sn(CH3)4) and deuterium in a DC helium glow discharge. The isotopic structure, the lambda-type doubling and the hyperfine splitting due to the tin nucleus could be resolved. A set of molecular parameters for the ground state is given.

ISSN:0026-8976    

DOI:10.1080/00268979100101761

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The quasielastic and inelastic neutron scattering spectra of the solid ordered, plastic and liquid phases of cyclopentane have been recorded in order to analyze the rotational, translational and conformational dynamics of this non-rigid molecule.

ISSN:0026-8976    

DOI:10.1080/00268979100101771

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A successful determination of a shielding anisotropy with electric field NMR is reported for the first time. The nucleus studied is the nitrile13C in liquid acetonitrile. From13C frequency changes and14N quadrupolar splittings upon dielectrical alignment, the chemical shift anisotropy of13C is found to be 378 ± 20 ppm. The14N quadrupole coupling constant is obtained from1H and14N spectra of the orientated molecule, giving a value of 3·47 ± 0·16 MHz.

ISSN:0026-8976    

DOI:10.1080/00268979100101781

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor