摘要:

The Raman spectra of the totally symmetric ν1(A1′) mode of an NO3-ion have been recorded in aqueous LiNO3, NaNO3, KNO3and NH4NO3solutions at various concentrations. The vibrational and rotational correlation functions have been calculated from the Fourier transform of the Raman profiles. Reorientation of the symmetry axis of an NO3-ion in the aqueous solutions may be represented by the inertial motion for short times (t ≲ 0·15 ps, jump angle 17°), and by the rotational diffusion for longer times (t ≳ 0·3 ps). An effective moment of inertia for short times has been found to beI⊥= 20 × 10-39g cm2, which suggests, as compared with the free NO3-valueI⊥0= 6 × 10-39g cm2, some association with the surrounding water molecules or cations. The mean-square torque acting on an NO3-ion from the moment analysis has been found to increase linearly with nitrate concentration. The torque on an NO3-ion in concentrated nitrate solutions is predominantly from other ions, while the contribution from an NO3--water interaction is small. It is concluded that the vibrational band width of 6–13 cm-1in these nitrate solutions is to be attributed to the pure vibrational dephasing, due to an NO3--water interaction in dilute solutions, and due to NO3--water and increased NO3--cation interactions in concentrated solutions. The contribution from the induced dipole-induced dipole resonance vibrational energy transfer has been found to be negligible.

ISSN:0026-8976    

DOI:10.1080/00268977800101801

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

We consider in three dimensions the Ornstein-Zernike equation for a two-particle correlation functionh(r) that satisfies the hard-sphere core condition,h(r) = -1 forr< 1, and a direct correlation function with a weak long-range oscillating tail,c(r) = lim ε exp (- εr) sin (λr+ ω)/r, forr> 1, ε → 0. This yields a theory of freezing that is a natural extension of the van der Waalsian theory of the liquid-gas transition.

ISSN:0026-8976    

DOI:10.1080/00268977800101811

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Integral equations are developed diagrammatically for atomic and molecular pair energies. The equations are solved with numerical basis functions by transforming the integral equations into linear algebraic equations with the introduction of a suitable quadrature formula. For the first time, pair energy diagrams are evaluated to infinite order, which include non-diagonal as well as the usual diagonal contributions. Preliminary calculations are performed on the correlation energy of the ground state of the helium atom using a numericalVN-1basis set. In the case of helium, the diagonal contribution to the total pair result is found to be in error by less than 5 per cent.

ISSN:0026-8976    

DOI:10.1080/00268977800101821

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The geometrical coefficients that are involved in the nuclear relaxation time (T1) of TCNQ salts are calculated. The model uses the spin-density distribution in TCNQ-which is obtained from MO calculations. The angular dependence ofT1is computed and compared to experiment in the particular case of (ϕ3AsCH3)(TCNQ)2. Although the theoretical values are rather strongly dependent on the model used for the spin-density distribution, the ratio of scalar coupling to dipolar coupling for the interaction of the electron spin with the TCNQ protons can be estimated to be 2·2–2·4. Measurements of the frequency dependence ofT1in (ϕ3AsCH3)(TCNQ)2and its cation deuteriated homologue lead to an absolute determination of the excition motion spectral density. Evidence is given for low-dimensional behaviour.

ISSN:0026-8976    

DOI:10.1080/00268977800101831

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

A general method for calculating the overall shape of the spectrum of vibronic induced transitions in transition-metal ion systems is developed. The vibronic structure is expressed in terms of a weighted sum of medium induced lorentzian lines located at the frequencies of the fundamental odd vibrations of the complex. Each of these lines is followed by a series of vibronic lines assigned to the combination frequencies with one or more even vibrations. The relative intensities of these combination lines are determined by the values of an intramolecular distribution which includes both the effects of geometry and frequency changes of the modes involved in the transition. Values of the linear and the quadratic parameter for the molecule can be estimated from a fit to the experimental spectra.

ISSN:0026-8976    

DOI:10.1080/00268977800101841

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Measurements of quasi-elastic neutron scattering have enabled us to characterize the rotational and translational dynamics of an ethylene molecule adsorbed in sodium zeolite 13X.

ISSN:0026-8976    

DOI:10.1080/00268977800101851

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Calculations are presented for three models of alcohols dissolved in carbon tetrachloride in the slow modulation limit. A number of liquid-state models is considered. The calculated bands differ markedly in some cases from the often assumed gaussian distribution. The Raman spectra of the OH-stretching vibration of methanol,t-butanol and adamantanol-1 in dilute CCl4solution are presented. It is concluded that the second moments of these bands compare well with the calculated values in two of the solvent models. The experimental bands are narrower than the computed bands, indicating some motional narrowing. Trends in the vapour-solution frequency shift are also well reproduced in the calculations.

ISSN:0026-8976    

DOI:10.1080/00268977800101861

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

In this paper the results of quantum-chemical calculations of the importance of multi-body effects (i.e. the deviations from pairwise additivity) for lithium are presented. In addition, we analyse the differences between the theoretical and recent experimental determinations of the stabilization energy of Li3. The principal conclusions of this study are (1) multi-body effects are large for this system, (2) the experimental value of the stabilization energy of Li3is probably incorrect.

ISSN:0026-8976    

DOI:10.1080/00268977800101871

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The OH stretching region in the Raman spectrum of water vapour has been observed and reproduced by computer simulation using rovibrational wave functions derived from the analysis of high-resolution absorption spectra. Relative intensity measurements allow the determination of the depolarization ratio and the ratio of the two non-vanishing second-order irreducible tensor components forv1. These quantities have been combined with the literature value for the cross section of this band to calculate the principal cartesian components of thev1derived polarizability tensor. The cross section for thev3vibration was also determined, and these results are considered in terms of the bond polarizability theory.

ISSN:0026-8976    

DOI:10.1080/00268977800101881

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The theory of Baramet al.[J. chem. Phys.,58,4558 (1973)] of magnetic resonance lineshape due to modulation of the zero-field splitting (ZFS) interaction for semi-integer spins, is extended to include the isotropic hyperfine interaction. General equations are derived for the whole range of tumbling rates. In addition specific equations are given for the relaxation matrix in the fast tumbling limit. When the tumbling rate is slower than the Larmor frequency but still faster than the hyperfine interaction and the second-order ZFS shift then only the -½ →½ hyperfine transitions are observed and explicit equations for their linewidths are derived. The theory predicts a marked dependence of the linewidth on the nuclear Zeemann azimuthal quantum numberM, in both the fast and slow tumbling regions.

ISSN:0026-8976    

DOI:10.1080/00268977800101891

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor