摘要:

High resolution FTIR spectra of CF379Br,12CF3I and13CF3I have been studied and analysed in the region of thev1CF3symmetric stretching fundamental which is accessible to CO2-laser pumping. Spectra with a resolution of 0.01 cm-1have been obtained at various temperatures.Jclusters were resolved and analysed by polynomial and simulation methods. In13CF3I a Fermi resonance betweenv1(veff= 1047.60 cm-1) and 4v60(veff= 1049·51 cm-1) has been established. For CF335Cl,12CF379Br and12CF3I the Fermi resonance betweenv1and 2v50has been analysed semiquantitatively. Further rotational resonances occur in12CF3I, which could not be assigned unambiguously, but are likely to be due in part tov3+ 3v6. The spectra of thev5fundamental near 550 cm-1have been obtained for CF3Br and CF3I at a resolution of 0·05 cm-1. Whereasv5appears to be unperturbed for CF379Br, for CF3I a Fermi resonance betweenv5andv3+v6and a rotational resonance ofv5with 2v6have been assigned. A set of recommended vibrational frequencies for12CF3I and13CF3I is given, and several effective rotational constants and anharmonic constants including Fermi resonance are quoted. The implications of the results for the I.R.-multiphoton excitation of these molecules are discussed briefly.

ISSN:0026-8976    

DOI:10.1080/00268978500101311

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Stark-Zeeman quantum beats (parallel electric and magnetic field-induced fluorescence modulation) are used to determine second-order Stark tuning coefficients for theF1andF2303andF1101upper levels of the NO2Ã-[Xtilde]5933 Å band, yielding effective excited state dipole moments of 0·22, 0·42, and 0·26 D, respectively, along thebaxis (bisector of the ONO angle).

ISSN:0026-8976    

DOI:10.1080/00268978500101321

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The structure and dynamics of 4-n-butoxybenzylidene-4′-n-octylaniline (40·8) have been investigated in the isotropic, nematic, and smectic phases using frequency dependent deuterium nuclear spin relaxation measurements of p-diethynyl-d2-benzene, a well-ordered spin probe. In the isotropic phase the existence of local nematic structure is revealed by frequency dependence of the spin-lattice relaxation rates. In the nematic and smectic phases, measurements of individual spectral densities of motion allow the separate determination of relaxation contributions from the reorientation of individual molecules and from long range, quasi-coherent director fluctuations. Director fluctuations contribute noticeably to spin relaxation only in the nematic and smecticAphases. In all phases, the reorientational motion of the probe is less strongly coupled to viscous modes than was found previously for this probe in a simple nematic solvent.

ISSN:0026-8976    

DOI:10.1080/00268978500101331

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Thermodynamic perturbation theories for molecular liquids usually need the equation of state (EOS) of a system of hard molecules. For molecules consisting of hard fused spheres the suggested EOS of Boublík needs the surface and the volume of such a hard body. In the present paper these quantities are calculated analytically for two types of molecules composed of hard spheres of equal radii the centres of which form either isosceles triangles or regular tetrahedra. Besides an elementary geometric calculation, a more fundamental approach is also used which allows an extension to molecules of more than four spheres the centres of which form regular polyhedra.

ISSN:0026-8976    

DOI:10.1080/00268978500101341

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Löwdin's formulae for the matrix elements of one- and two-electron operators between determinantal wavefunctions of non-orthogonal spin-orbitals have been modified for the case in which the actualN-electron determinants containn-excitations from a reference determinant. Use of algebraic techniques gives a compact general formula expressing the cofactors of the inverse of the actual overlap matrix in terms of the cofactors of a smaller matrix of ordern. Besides saving computational time, this formula survives even when the inverse of the overlap matrix does not exist owing to singularity problems, and it simplifies and generalizes previous work by Hayes and Stone, being particularly useful in CI or in perturbative studies including electron exchange.

ISSN:0026-8976    

DOI:10.1080/00268978500101351

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The results ofab initioSCF MO calculations on ethyl methylsulphide using various basis sets are presented. The geometrical parameters were reproduced very well by the 3-21 G +d(0·8C + 0·6S) set. Using this basis set, the MP2 perturbation procedure was applied to include electron correlation. This procedure explained very reasonably the relative conformational stability of the trans and gauche forms, which has been studied for a long time with difficulty because of their small energy difference. From these calculations, the contradictions between the results proposed by spectroscopists and theoretical chemists were clarified.

ISSN:0026-8976    

DOI:10.1080/00268978500101361

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

An extensive measurement of the microwave spectrum of the NCO radical has been made on the[Xtilde](0, 0, 0)2Πiand[Xtilde](0, 1, 0)2Δistates, and the spectrum in the[Xtilde](0, 2, 0)2Φistate was also observed for the first time. From an analysis of the observed spectrum, the rotational, centrifugal distortion, spin-rotation coupling, and hyperfine coupling constants includingeQq2, the non-axially symmetric nuclear quadrupole coupling constant, were determined to good precision. The observed vibronic dependences of the hyperfine and spin-rotation coupling constants were discussed.

ISSN:0026-8976    

DOI:10.1080/00268978500101371

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Electron spin echo techniques in combination with laser flash excitation have been used to study the spin relaxation processes in the triplet state of inequivalent naphthalene dimers in zero field down to 0·35 K. The spin-spin relaxation is dominated by a fast spin-lattice relaxation induced by a thermally activated exchange process between the two Davydov components. The technique allows us to obtain selectivelyS1←S0excitation spectra which show that energy transfer is slow compared to the spin relaxation rates.

ISSN:0026-8976    

DOI:10.1080/00268978500101381

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The thermodynamical properties of systems containing rigid rod molecules without attractive interactions were studied by Monte Carlo simulations on the square lattice. Calculations were made for some values of length-tobreadth ratio of rod over a wide range of density. The excess chemical potential, order parameter and equation of state were derived for systems under consideration. Differences between predictions of mean field approximation lattice theories (Flory and DiMarzio) and simulation results were discussed. For solutions of considerably long rods a transition from an isotropic to an anisotropic phase was observed. Conditions in which this phase transition occurs were discussed.

ISSN:0026-8976    

DOI:10.1080/00268978500101391

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The normalized density power expansion of the mean potential at contact distance is calculated for seventeen hard repulsive body fluids. It is shown that first coefficients of the virial series strongly decrease with increasing order. Thus only a very few virial coefficients of the mean potential at contact distance are necessary to calculate the compressibility factor within a few percent through the pressure equation for stable fluid densities. A semiempirical equation of state is proposed for hard repulsive body fluids using two shape factors which are simple analytical functions of the second virial coefficient of the compressibility factor and a mean length to breadth ratio.

ISSN:0026-8976    

DOI:10.1080/00268978500101401

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor