摘要:

Estimation of the complex polarizability of the itinerant oscillator (I.O.) model of polar fluids has hitherto been based on a truncation of the series expansion of the double transcendental function describing the decay of the dipole moment. The essence of this method is to expand the decay function as a series of single transcendental functions. The resulting series is then Fourier transformed term-by-term by means of the usual response theory formula. The series is generally truncated after the first two terms so as to yield simple analytic formulae analogous to the Rocard equation. Corcoran has developed a numerical algorithm using Fast Fourier Transform techniques which allows the complex polarizability to be calculated to a high degree of precision from the decay function without recourse to any series expansion. The numerical method shows that the analytic approximations to the polarizability which have hitherto been used are quite accurate. Furthermore, if friction does not act on the inner dipole (the form of the model which has hitherto been almost exclusively used to represent spectra), it is found that the moment of inertia of the outer cage should be less than that of the inner dipole in order to achieve a good fit with the experimental data. This conclusion is inconsistent with the physical concept of the I.O., namely a dipole surrounded by a cage of neighbours, and has led to much criticism of the model. On the other hand, when friction acts on the inner dipole and is approximately the same (per unit inertia) as that acting on the outer cage, the model can produce physically realistic spectra for acceptable parameter values. This suggests that the two-friction form of the model should always be used for comparison with experimental spectra.

ISSN:0026-8976    

DOI:10.1080/00268978700100941

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The complex polarizability of the itinerant oscillator model in the case where the stochastic torques are weak in comparison with the deterministic ones may be evaluated analytically in terms of a series involving the modified Bessel functions. This clearly shows the existence of a harmonic peak structure at high frequencies. In the case where the stochastic torques are significant the complex polarizability may not easily be evaluated analytically but may be calculated to a high degree of accuracy using numerical Fourier transform techniques developed by Corcoran. These techniques show that the harmonic peak structure still persists when the friction in the system is significant, but those peaks of higher order with respect to the fundamental frequency are so small in amplitude when friction acts on both dipole and cage of the model system that they are almost imperceptible. If on the other hand frictional torques are supposed to act only on the cage as in earlier versions of the model a distinct peak structure still persists.

ISSN:0026-8976    

DOI:10.1080/00268978700100951

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

High resolution Fourier transform spectra have been used for an extensive analysis of the 2v1+v2,v1+v2+v3andv2+ 2v3bands of H232S and H234S in the 6000–6500 cm-1region. Using a hamiltonian which takes explicitly into account the Coriolis interaction between the rotational levels of the (111) vibrational state with those of the (210) and (012) vibrational states together with the Darling-Dennison interaction between the (012) and the (210) states, it has been possible to reproduce satisfactorily the rotational energy levels of these three interacting states, and a precise set of vibrational energies and rotational and coupling constants has been derived. Moreover, individual intensities of transitions belonging to the 2v1+v2,v1+v2+v3andv2+ 2v3bands of H232S have been estimated, leading to the determination of the transition moment constants appearing in the expansion of the transformed transition moment operators of these three bands. Finally a complete listing of the positions and intensities of the H232S and H234S lines absorbing in the 1·6 μm region has been generated.

ISSN:0026-8976    

DOI:10.1080/00268978700100961

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The shear viscosity of n-butane has been computed by the method of molecular dynamics (MD), by both the Green-Kubo technique and a non-equilibrium method employing a weak fictitious external field inducing a symmetric velocity gradient (pure deformational flow). In this last case, non-equilibrium segments, starting from equilibrium configurations, were averaged, the subtraction technique being used to measure the signal out of noise.

ISSN:0026-8976    

DOI:10.1080/00268978700100971

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Infrared fluorescence of Rb2in the region 6800-8000 cm-1, arising when the levels of theC1Πustate are pumped by the 472·7, 476·5, 488·0 and 496·5 nm lines of an argon-ion laser, has been recorded by Fourier transform spectrometry. The fluoresence is assigned to the systemC1Πu→ 21Σ+g. The 21Σ+gstate energy levels up tov= 24 have been determined. The main spectroscopic constants for this 21Σ+gstate are

ISSN:0026-8976    

DOI:10.1080/00268978700100981

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Laser induced fluorescence detection of reaction products is now a wide-spread technique. When the laser coherence time is longer than the time spent by a molecule in the laser beam, the saturation effects of the laser-molecule interaction cannot be described by rate equations. In this paper we present a simple theoretical description of these effects and detailed experimental verifications. These results are quite important if one wants to derive reliable population measurements from the laser induced fluorescence signals in the case of coherent saturation.

ISSN:0026-8976    

DOI:10.1080/00268978700100991

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Determinations of electronic transition moments rely generally on ther-centroid approximation. This method is no longer valid when, in the stationary phase approximation, two transition points occur. A purely quantal treatment is applied here to the determination of electronic transition momentsMe(r) from both line intensities and lifetime measurements for the 1g(3P2) →A1uand 0+g(3P2) →B0+utransitions of the I2molecule.

ISSN:0026-8976    

DOI:10.1080/00268978700101001

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The 1gand 0+g(3P2) ionic states of iodine interact via the rotational hamiltonian. The resulting Ω doubling in the 1gstate is studied in detail. A value of 103is deduced for the ratio of the transition probabilities of the 0+g←Band 1g←Btransitions. A complete interpretation of their relative intensities involves saturation effects which are clearly observed for the 0+g←Btransition. The results give a complete explanation as to why the 0+gstate was the only one to be excited in this spectral region by former workers.

ISSN:0026-8976    

DOI:10.1080/00268978700101011

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

New anisotropic potential energy surfaces of the Hartree-Fock plus damped dispersion (HFD) type have been obtained for the N2-Ne and N2-Ar interactions. The SCF energies utilized in constructing the short-range part of the interactions were computed at 20 points on each surface by using basis sets of double zeta plus polarization quality. AnisotropicC6andC8dispersion coefficients, utilized in constructing the long-range part of the interaction, have been calculated with a recently obtained combining rule. Several procedures are introduced for estimating the anisotropic damping factors used in the description of the correlation energy contributions in the HFD model. The essential differences amongst the surfaces reported here arise from these estimates. Comparisons are made with other available anisotropic N2-Ne and N2-Ar surfaces. The predictive ability of all surfaces with respect to the temperature dependence of the interaction second virial coefficient,B12(T), has also been tested. For the N2-Ne system only the present HFD3 surface gives good agreement with the experimental interaction second virial coefficients over a wide temperature range. Similarly, for the N2-Ar system the surface of Candoriet al.[1983,Chem. Phys. Lett.,102,412], which was partially determined using the second virial coefficient data, and the present HFD1 surface give good agreement with experimental virial data.

ISSN:0026-8976    

DOI:10.1080/00268978700101021

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The isothermal enthalpy relaxation of glassy 1,2,6-hexanetriol has been measured at six temperatures. The relaxation time and the distribution parameters extracted from fits of the Williams-Watts relaxation function are compared with parameters obtained by other techniques and on other substances. A detailed comparison of the Williams-Watts and the Davidson-Cole relaxation functions is presented.

ISSN:0026-8976    

DOI:10.1080/00268978700101031

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor