摘要:

The temperature dependence of the dipole polarizability α(λ,T) of free atoms and molecules is determined by precise measurements of the refractive indexnof gases in the extended temperature range between 300 K and 1100 K for wavelength λ = 632·99 nm, using a specially constructed Michelson twin interferometer. α of the noble gases is observed to be independent ofT. α of the molecular gases H2, N2, O2, and CH4increases with increasing temperature by an amount of approximately 1 per cent per 1000 K. These results are in excellent agreement with theoretical predictions. They will be compared to previously measured temperature dependent polarizabilities.

ISSN:0026-8976    

DOI:10.1080/00268979000100611

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A new interferometric method is used to determine the temperature dependence of the dispersion of the polarizability α of gaseous argon, hydrogen and oxygen, respectively. Although only the small wavelength range between 543·51 nm and 632·99 nm is covered, the data obtained in the temperature range 300 K <T< 1010 K are useful to derive important molecular properties like effective oscillator strengths and excitation energies, dispersion energy constants, and polarizability derivatives.

ISSN:0026-8976    

DOI:10.1080/00268979000100621

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Proton solid-echo transverse relaxation functions for many thermotropic and lyotropic mesophases, mapped by measurement of the echo amplitudeSyx(t′ = τ) as a function of τ using aPy(90°)-τ-Px(90°)-t′ sequence, yield gaussian behaviour of the form exp [-½ME2τ2] for decays up to 20–30 per cent of the value at τ = 0.ME2, the second moment for the dipolar interactions between the spin-½ pairs, is related to the van Vleck second momentMVV2through a factorf. Whilst experiments suggested a value of 0·70–0·72 forf=ME2/MVV2, simple models that ignored the non-equivalence of the dipolar-coupled spin-pairs had predictedf= 0·65. In this paper we derive an exact analytic expression for the spin response of a model of two dipolar-coupled inequivalent spins-1 to the pulse sequencePy(90°)-τ-Pα(β)-t′, and show that the present model, with the quenching of the spin-flip terms of the dipolar hamiltonian, resolves the afore-mentioned discrepancy. We also reconcile the differences between the experimental and the earlier predicted values offfor deuteron N.M.R. spin echoes in perdeuterated solids.

ISSN:0026-8976    

DOI:10.1080/00268979000100631

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Direct observations of infrared absorption in the weakly bound dimer of carbonyl sulphide, produced in pulsed molecular beams, have been made. Diode laser spectra in the 5 micron, carbonyl stretching, wavelength region were recorded with FWHM linewidths of approximately 100 MHz. All of the observations are consistent with OCS dimer having aC2h, centrosymmetric geometry, with the centres of mass of the monomers nearly opposite one another. This essentially perpendicular structure places the S atoms close to the centre of the complex. The perpendicular distance between the monomer axes is 3·64 Å. Intermolecular potential functions containing dispersion and electrostatic contributions are discussed.

ISSN:0026-8976    

DOI:10.1080/00268979000100641

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The chemical potential of liquid xenon is determined by constant-TVN Monte Carlo simulation for 17 states mostly at high density. A slightly modified version off-g-sampling is used together with a simple and efficient lattice method for inserting test particles. The model, which contains pair and three-body interactions, leads to small but significant deviations from experimental values of the chemical potential. The functional derivative of μ with respect to the pair potential and the derivative of μ with respect to a parameter of the three-atom potential are computed in two different ways and the results are compared.

ISSN:0026-8976    

DOI:10.1080/00268979000100651

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

An extensive investigation of the thermodynamic properties of xenon is reported. Computer simulation is used to extract information on many-body interactions from experimental data. It is shown by means of statistical arguments that long-ranged three-atom potentials, derived by multipole expansion and combined with an accurate pair potential, cannot explain the data within the required accuracy. In contrast to this, several three-atom potentials which do so have been found.

ISSN:0026-8976    

DOI:10.1080/00268979000100661

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The polaron theory of electrons solvated in molten salts is applied to dilute solutions of Cs in molten CsI. Structural and thermodynamic properties of the excess electron and of the surrounding liquid are calculated as well as the electronic absorption spectrum which is compared with the result of optical studies. The influence of the electron-cation attraction on the electron localization is discussed within the model considered.

ISSN:0026-8976    

DOI:10.1080/00268979000100671

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Qualitative and quantitative aspects of the semiclassical method using rotational energy surfaces, are studied. These surfaces are determined for triatomic molecules by applying the rigid-bender model. A relation between the topology of the rotational energy surfaces and the structure of rotational multiplets is analysed. The semiclassical tools are used to determine properties of quantum ro-vibrational states.

ISSN:0026-8976    

DOI:10.1080/00268979000100681

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Numerous microwave transitions between the Λ-doubling components of vibrational levels in theX2Δ3/2(v= 0) state of NiH in the gas phase have been measured using the technique of microwave-optical double resonance (MODR) spectroscopy. An effective experimental method for the simultaneous introduction of low-frequency microwave radiation and optical laser radiation into a flowing reaction chamber has been demonstrated. Some Λ-doubling and magnetic hyperfine parameters were obtained from a least squares fit of an effective hamiltonian model to the observed transition frequencies. The spectroscopic parameters are interpreted in terms of the proposed electronic wavefunctions and state distribution.

ISSN:0026-8976    

DOI:10.1080/00268979000100691

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Measurements have been made, in thin films of poly-N-epoxypropylcarbazole, of the absorption coefficient, the activation energy of photogeneration and the photogeneration efficiency of charge carriers as functions of the concentrations of electron acceptors from the fluorene series. They have demonstrated a correlation between the localization radius of the excess electron in an acceptor molecule and the activation energy of photogeneration within the absorption region of a charge-transfer complex.

ISSN:0026-8976    

DOI:10.1080/00268979000100701

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor