摘要:

Low-lying singlet, triplet and quintet states of BO+were studied by configuration-interaction methods. The ground state is found to be 11Σ+, with 13Π only 0·3 eV higher in energy. Many stable states are predicted, similar in structure and ordering to those of BeO and BN. Three Π states, 21Π, 23Π and 15Π, have unusually flat minima at large values ofR.Vertical and adiabatic ionization potentials of BO for removal of the 5σ and the 1π electron are given. Dipole moments for the three lowest states of BO+are also reported.

ISSN:0026-8976    

DOI:10.1080/00268978700101651

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Methods for obtaining a static dielectric constant ϵ from measurements of mean square dipole moment in a simulation are discussed. The simulations are seen as models of a macroscopic experiment to measure the dielectric constant. Such an experiment is usually carried out on a macroscopic sample of fixed shape. This sample is modelled by an array of copies of a microscopic simulation sample, the array having the appropriate shape. The different shapes correspond to different macroscopic experiments. The periodic boundary condition simulation sample hamiltonians appropriate to some different macroscopic geometries are described and appropriate fluctuation formulae for the dielectric constant obtained. The formulae are illustrated by simulations of fairly weakly dipolar molecules (which are rigid models of methyl chloride molecules) using samples of 27, 64, 125 and 216 molecules. All sample sizes give the same dielectric constant to within the error in the simulations, but the structure obtained for 27 molecules seems slightly distorted by small sample sizes. The measured wavevector dependent dielectric tensor ϵ(k) appears able to be extrapolated tok= 0 to agree with the values of ϵ obtained.

ISSN:0026-8976    

DOI:10.1080/00268978700101661

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The gas-phase absorption spectra of12CO2and13CO2between 880 and 2000 Å, at a resolution limit of 0·008 Å, were recently photographed dy Cossart-Magoset al.Rotational structure observed at 1106 Å was then assigned to absorption to the … 1π3g3pπu3Σ-uRydberg state. The whole region between 898 and 1145 Å is now analysed.Ab initiocalculations are carried out to estimate the energy of the lower Rydberg states of thes,p,dandfseries converging to[Xtilde]2ΠgCO+2.nftransition bands are characterized by sharp features in their rotational contours and assigned fromn= 4 ton= 28 and 32, respectively for the limits Ωc= 3/2 and 1/2 in the[Xtilde]2Πgstate of the ion core. A new value of the first ionization potential of CO2results: 111 201 ± 2 cm-1(average of the two limits).nptransition bands, with the exception of the 1106 Å band referred to above, are diffuse, and were assigned by a method based on comparison of experimental and calculated quantum defects plotted against the reduced term energies. Up ton= 6, energy intervals corresponding tonpσ andnpπ configurations do not overlap andnpσ is found to be at higher energy thannpπ. The bending frequencyv2is observed with ν′2= 11Πustates (… 1π3gnpσu(n= 3 - 7) and … 1π3u1π4g3sσgconfigurations); the symmetric-stretching frequencyv1is observed withv′1= 1 in the same states and in those belonging to thenfseries (n= 4 - 9). Partial evidence is found to assign forbiddennsandndterms forn⩽ 4 (ion core … 1π3g). The corresponding bands are diffuse. An interpretation of the diffuse character of most bands in the spectra is considered in terms of interaction of the corresponding Rydberg states with dissociative valence states.

ISSN:0026-8976    

DOI:10.1080/00268978700101671

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Compressibility factors and structure in terms of site-site and centre-centre radial distribution functions are obtained for several hard polyatomic molecular fluids by means of Discontinuous Molecular Dynamics. Linear molecules with 3, 4 and 5 atoms, tetrahedral and hexagonal molecules at various densities are studied. Compressibility factors are compared with convex body equations of state based in the Scaled Particle Theory. A Monte Carlo method is used to calculate the volume and surface area of the molecules. Radial distribution functions are compared with Monte Carlo and RISM results. Equivalence of Molecular Dynamics and Monte Carlo results is established as well as the suitability of Scaled Particle Theory equations to represent the thermodynamics of such systems.

ISSN:0026-8976    

DOI:10.1080/00268978700101681

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Approximate formulae from momentum-transfer theory for the mobility and diffusion coefficients of ions in gas mixtures are tested. Most of the test ‘data’ are simulations obtained from moment solutions of the Boltzmann equation. The mobility formula works well, but requires some simple iteration; a linearized version proposed to avoid the iteration can fail badly in some cases. The formulae for ion diffusion, here tested for the first time, are less successful because of approximations made to find the ion temperatures perpendicular and parallel to the electric field, but nevertheless give a useful qualitative accuracy. The results properly apply to systems undergoing only elastic collisions, but some limited results on the influence of inelastic collisions are given.

ISSN:0026-8976    

DOI:10.1080/00268978700101691

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

We derive two formally exact expressions for the temperature derivative of an arbitrary mechanical property of the non-equilibrium steady state. Applying these expressions to the internal energy, we obtain two formulae for the specific heat of the steady state. One of these shows that the specific heat can be calculated by analysing fluctuations in the steady state. The second formula relates the steady state specific heat to the transient response observed when an ensemble of equilibrium systems is perturbed by the field.

ISSN:0026-8976    

DOI:10.1080/00268978700101701

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A time dependent fluorescence depolarization experiment is reported and fully analysed for the first time for a probe dissolved in an aligned nematic liquid crystal. We have investigated the popular dye all trans 1,6 diphenyl hexatriene in the transparent mesophase mixture ZLI-1167 at a series of temperatures within the nematic and isotropic range. The probe order parameter <P2> and perpendicular rotational diffusion coefficient have been determined, together with the fluorescence lifetime τFin the liquid crystal and isotropic phase. This information is extracted applying a previously proposed theory for rotational fluorescence depolarization in a mesophase (Zannoni, C., 1979,Molec. Phys.,38,1813) and introducing a global variant of the target analysis deconvolution procedure presented earlier (Arcioni, A., andZannoni, C., 1984,Chem. Phys.,88,113). Our results demonstrate the possibility of employing fluorescence depolarization as a useful technique for investigating aligned mesophases.

ISSN:0026-8976    

DOI:10.1080/00268978700101711

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The use ofab initioHartree-Fock electric field gradient calculations to predict nitrogen nuclear quadrupole coupling constants is examined using basis sets of split valence to triple zeta plus polarization size. From results on 20 to 35 molecules for each basis, such calculations are shown to be of predictive value if systematic errors are eliminated by using regression-derived scaling factors, and the reliability of each basis is assessed. For field gradient calculations on larger molecules, a significantly better alternative to a minimal basis which adds little extra computational cost, is proposed.

ISSN:0026-8976    

DOI:10.1080/00268978700101721

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The spin-coupled valence bond method is used to calculate potential energy curves of1Π symmetry for the process C3+(2s) + Li(2p) → C2+(nln′l′;1L) + Li2+(1s2). A total of ten states is considered and several crossings are found. Excitations into virtual orbitals of δ symmetry are found to make important contributions to the correlation energy. Future work will concentrate on the calculation of matrix elements of δ/δRfor this and related systems.

ISSN:0026-8976    

DOI:10.1080/00268978700101731

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Polarized and depolarized Raman spectra of room temperature liquid H2O and D2O have been measured up to the bending region. Both spectral shapes and depolarization ratios are analysed in the translational and librational regions. An isotropic spectral component extending over all the investigated frequency range is derived and interpreted in terms of interaction induced mechanisms involving the polarizabilities of the isolated molecule.

ISSN:0026-8976    

DOI:10.1080/00268978700101741

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor