摘要:

The nuclear resonance photon scattering (NRPS) cross section σsfrom15N in the form of NO adsorbed on activated carbon fibre (ACF) was studied as a function of temperature in the range 15 K – 300 K. The value of σswas found to be much higher than that from a pure NO sample. The increase in σsamounted to about 14 per cent at 297 K and 45 per cent at 15 K, and is explained by the effect of the strong binding NO-ACF potential and in terms of the dimerization of adsorbed NO on ACF. The magnitude and the behaviour of the scattering cross section may probably be used as an indicator of the occurence of chemical adsorption. The average zero-point energy of the binding potentials are deduced using a simple model.

ISSN:0026-8976    

DOI:10.1080/00268979000100541

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A neutron diffraction study of the atomic structure of deuterated molten ammonium nitrate (N(1)D4N(2)O3) was carried out at 453 K. The first and second order isotopic difference methods of neutron diffraction were applied to the nitrogen nuclei of the ammonium and nitrate ions. The results of the total and the first order differences demonstrate the existence of stable ND+4and NO-3ions in the melt. The ND+4ions conform to a tetrahedral geometry and the NO-3ions retain aD3hsymmetry arising from a triangular geometry. The second order difference enabled the determination of the ‘cross’ pair distribution functiongN(1)N(2)(r), from which it was concluded that the crystal structure relaxes significantly on melting.

ISSN:0026-8976    

DOI:10.1080/00268979000100551

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Using the extended thermodynamic perturbation theory of Wertheim, closed simple analytic expressions for the internal energy and pressure of the primitive model of water are derived and examined in detail. The equation of state, which has a form of a perturbed hard sphere equation, exhibits the same anomaly in temperature dependence of the isothermal compressibility as real water. The low value of the critical compressibility factor is in close agreement with the experimental value for real water.

ISSN:0026-8976    

DOI:10.1080/00268979000100561

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The structural features of model quasi-one-dimensional systems have been elucidated which favour the formation of the singlet or the ferromagnetic ground state. For this purpose the spin extended Hartree-Fock PPP calculation is employed taking into account electron correlation. The decisive role is played by the extent of the orbital degeneracy (or quasi-degeneracy) amplifying the electron correlation effects.

ISSN:0026-8976    

DOI:10.1080/00268979000100571

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The direct solution of two inhomogeneous ordinary differential equations provides a simple method of calculating accurate non-adiabatic matrix elements when the basic adiabatic wavefunctions are obtained on a grid by finite difference techniques.

ISSN:0026-8976    

DOI:10.1080/00268979000100581

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The absorption coefficient, α, and refractive index,n, of water have been measured in the millimetre and submillimetre frequency region (50–300 GHz). The measurements were carried out using a free-space technique at room temperature with backward wave oscillators as the sources. The measured values of α andnare presented and discussed in comparison with the existing literature data.

ISSN:0026-8976    

DOI:10.1080/00268979000100591

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A new six-dimensional analytical potential energy surface for the hydrogen bonded dimer (HF)2is presented. It is based on theab initiostudy by Kofraneket al., and uses 1070 points with energies up to 500 kJ mol-1as well as recent correlated dispersion coefficients from a perturbation treatment by Rijks and Wormer, and the experimental Morse parameters for the HF monomer. The fit to theab initiopoints contains 29 free and several constrained parameters and has a weighted standard deviation of 29·5 cm-1. A brief description of some properties of the new surface is given. Preliminary results of a diffusion quantum Monte Carlo (QMC) study for vibrational energy levels on the new surface as well as on a surface published by Bunkeret al.are given. An interesting anharmonic isotope effect in thev6fundamental is discussed and explained.

ISSN:0026-8976    

DOI:10.1080/00268979000100601

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor