摘要:

Carbon-13 and silicon-29 spin-lattice relaxation times and the corresponding nuclear Overhauser enhancements have been measured for PhnXH4-n(n= 1-4,X= C or Si). Thence dipolar and other contributions to the relaxation rate have been separated. The dipolar contribution is dominant, except for -CH3and -SiH3groups. Correlation times for overall molecular motion have been estimated, andT1ratios for phenyl groups have been used to compare the rotational mobility of the phenyl groups. Internal molecular motion is more hindered in phenylmethanes than in phenylsilanes. Results for diphenylmethane and diphenylsilane are consistent with strong coupling between internal and overall molecular motion.

ISSN:0026-8976    

DOI:10.1080/00268978500100811

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A simple method is used to calculate a set of correlation functionsPj(r) which give the probability that a point at distancerfrom a sphere centre hasj, and onlyj, sphere centres within one diameter, σ. The functionP1(r) gives the ‘cavity-cavity’ correlation functiony(r) =g(r) exp (βu(r)) in the range 0 <r< σ, whereP1(r) =y(r)/y(0), and it gives the pressure and chemical potential efficiently. The calculated values ofy(r) conform to the simple expression In {y(r)/y(0)} = ΔV(r){a1+a2r} where ΔV(r) is the change in the volume excluded to the system when a pair of cavity sites are separated fromr= 0 tor.a1anda2are determined by exact thermodynamic relations. Results are reported for the hard disc and sphere fluids.

ISSN:0026-8976    

DOI:10.1080/00268978500100821

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The modified hypernetted chain (MHNC) theory is used to determined the structure of a dispersion of charged colloidal particles interacting via screened coulomb interactions. The calculated radial distribution functions are found to be in good agreement with those from computer simulation studies of the same system and considerably superior, both qualitatively and quantitatively, to the predictions of models based on the mean spherical approximation.

ISSN:0026-8976    

DOI:10.1080/00268978500100831

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Infrared integrated intensities, measured for vibration-rotation bands of C2D2, N2O and CO2compressed with argon and krypton, are found to be a linear function of the rare gas density up to 250 amagat. Above this density and up to 468 amagat, a departure from linearity is observed in the study of thev3band of CO2in krypton. An attempt of interpretation is made considering induced and local field effects. It is shown that the latter is largely predominant and able to explain the observed density dependence. Moreover questions concerning the size of the cavity intervening in the model are discussed. It is concluded that this size is independent from the density of the medium.

ISSN:0026-8976    

DOI:10.1080/00268978500100841

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A fluid whose molecules are pairs of hard discs can serve as a reference system for the study of adsorbed diatomic molecules. We obtain its second virial coefficient, point out an ambiguity in the definition of this coefficient when the separation of the centres of the disc exceeds √2 times their diameter, and compare the results with those for a capped rectangle, which is the equivalent hard convex body.

ISSN:0026-8976    

DOI:10.1080/00268978500100851

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A new approach to the problem of the electrostatic effects on the molecular orientation in interphases is proposed. This is based on a first order perturbation theory developed within the density functional formalism. The theory includes for the first time the effects of the spatial charge distribution of the molecules on the interphase structure. Numerical calculations for the SSLJ-PC model (site-site Lennard-Jones interaction plus coulombic interaction of an array of point charges) is presented. The results are compared with those obtained from other theories and from MD calculations. The qualitative agreement with simulation results is good. A discussion of the cutoff distance used in the computer simulations is included.

ISSN:0026-8976    

DOI:10.1080/00268978500100861

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

We develop a simple model for the calculation of the splitting between molecular states of the heteronuclear rare gas ions. Making use of available experimental data we determine the potential curves themselves. The accuracy is estimated to be sufficient to aid the interpretation of collision experiments. Further, our results suggest a new assignment of the already observed charge exchange transitions. The relative energy positions of the potentials should be reliable enough to predict the transition energies of the so far unobserved bands within a few meV.

ISSN:0026-8976    

DOI:10.1080/00268978500100871

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

We present energy spectra of electrons formed in the reaction of He(23S, 21S) with NO2which have significantly improved counting statistics and resolution compared to earlier work. Further, we show spectra of the fluorescence light emitted in these reactions. The data are recorded in the same molecular beam apparatus as the electron spectra. For the metastable singlet state He(21S) the spectra have not been measured before. We find that in addition to ionization excitation transfer takes place into Rydberg states of NO2**. Subsequently, the highly excited NO2** molecules dissociate into NO and atomic O* Rydberg atoms.

ISSN:0026-8976    

DOI:10.1080/00268978500100881

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

We derive the equations which determine the free energy, and other thermodynamic and structural properties, including the high-frequency dielectric constant, of a dipolar-quadrupolar polarizable liquid at the second level of renormalized perturbation theory (2-RPT). Our treatment is non-graphical and is based on simple arguments from electrostatics. The significance of the various parameters which enter the renormalized theory is discussed. Our results provide the starting point for calculations of the effects of many-body induction forces in molecular liquids.

ISSN:0026-8976    

DOI:10.1080/00268978500100891

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

We generalize Wertheim's 1-R renormalized perturbation theory for polar, polarizable fluids to mixtures in which the molecules possess dipoles and quadrupoles. The theory is used to calculate thermodynamic excess functions and phase equilibria for a variety of model mixtures, and comparisons with experiment are made for three binary mixtures. The results demonstrate the importance of accounting for many-body induction effects and for anisotropy of the polarizability. The additional induction effects due to the presnce of the quadrupole are appreciable provided one or more of the molecular species in the mixture possesses a dipole, but are small otherwise.

ISSN:0026-8976    

DOI:10.1080/00268978500100901

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor