摘要:

Effects of the spin-orbit HamiltonianHLS, including both the spin-same orbit and spin-other orbit terms, are studied at the self consistent field (SCF) level of theory. Separate calculations are carried out for each state considered, and biorthogonal orbitals are constructed for the evaluation of matrix elements. Doublet-doublet and singlet-triplet interactions are discussed. The evaluation of the Gaussian basis function integrals is described in a Cartesian component representation, these integrals being directly related to one and two electron second derivative integrals. This new SCF spin-orbit code is used to (i) determine the spatial dependence of the spin-orbit parameters for the Renner-Teller2B1,2A1states of H2O+, (ii) determine the spin-orbit splitting of the2Π states of OH as a function of bond-length and (iii) calculate the radiative lifetime of thea3Σ+state of NO+. In each case these calculations are compared with more sophisticated configuration interaction studies, but it is found that the evaluation of these effects near equilibrium geometries at the SCF level is sufficiently accurate, provided that a large basis set is used.

ISSN:0026-8976    

DOI:10.1080/00268979300102411

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Quantum mechanical continuum models of solvation, the self-consistent reaction field (SCRF), and polarizable continuum method, are used at theab initioSCF level, to study tautomer equilibria, partition coefficients and amine basicity. The predictions are compared both with experimental data and with results from free energy perturbation (FEP) studies. In the SCRF studies, the description of the solute charge distribution beyond the dipole level does not lead to a significant improvement in the accuracy of the predictions. For the range of properties studied, the quality of predictions by these continuum models rivals that obtained by traditional molecular dynamics calculations.

ISSN:0026-8976    

DOI:10.1080/00268979300102421

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

860 rotational ines of the almost unperturbedv∓14+v∓16component of thev4+v6band of CH379Br have been assigned in spite of overlaps with several other bands. Only a few sub-bands (KΔK= 1, -7, -8, -9) are subject to slight resonances. An RMS deviation of 0·0039 cm-1has been achieved by a leastsquares fit of 742 lines. As expected, theA′,B′,D′J,D′JKandD′Kmolecular conparison between the centres of both components of thev4+v6band allowed us to measure two anharmonicity constants:x46= -5·25 cm-1andg46= 0·89 cm-1.

ISSN:0026-8976    

DOI:10.1080/00268979300102431

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The totally symmetric ring modes of benzene, benzene-d6, pentafluorobenzene, hexafluorobenzene, cyclopentane, cycloheptane, cyclopentanone, cyclohexanone were investigated with customary Raman devices. For the first time it is shown that a negative or anomalous noncoincidence effect seems to be a general property of aromatic and aliphatic ring vibrations. In agreement with the results of isotopic dilution experiments carried out with benzene and benzene-d6this new effect is explained in terms of the pair excitation model as a result of a dominant repulsive resonant intermolecular vibrational coupling.

ISSN:0026-8976    

DOI:10.1080/00268979300102441

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Ab initiomany body perturbation theory is used to calculate the imaginary frequency multipole polarizabilities of N2, Cl2, CO, HCl and HBr as a function of bond length. These are combined with previously calculated dynamic polarizabilities for rare gas atoms to obtain the intramolecular bond length dependence of the anisotropic dispersion and induction coefficients throughR-8for AB-X (AB = N2, Cl2, CO, HCl, HBr and X = He, Ne, Ar, Kr, Xe) interactions.

ISSN:0026-8976    

DOI:10.1080/00268979300102451

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A comprehensive and general group theoretical analysis is presented of the time correlation functions (TCFs) governing nuclear spin relaxation in anisotropic systems such as liquid crystals and molecular solids. Without invoking specific dynamic models, the consequences of time-reversal invariance (detailed balance) and rotational symmetry are explored systematically. By constructing TCFs from irreducible tensor components adapted to the crystal symmetry and making use of group theoretical orthogonality relations, the most general and concise expression of the orientation dependence of the labframe TCFs is derived. Depending on the crystal symmetry, there are between 2 and 15 coefficients in this expression: these are the irreducible crystal-frame TCFs associated with the irreducible representations of the crystal point group. The corresponding irreducible crystal-frame spectral densities constitute the complete model-independent information content derivable from spin relaxation experiments. Explicit expressions for the irreducible crystal-frame TCFs and the associated angular functions are given for all crystallographic point groups. The combined effect of crystal symmetry and local (microstructure) symmetry is also investigated, as is the effect of symmetry on TCF contributions from motions on multiple time scales. Furthermore, the relation of the TCFs to the independent order parameters is established. While many of the new results are applicable to a wide variety of spectroscopic techniques and systems, the explicit results have their greatest potential for spin relaxation studies of oriented lyotropic liquid crystals.

ISSN:0026-8976    

DOI:10.1080/00268979300102461

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Delayed ionization of C60on the microsecond timescale has been investigated following 193 nm excitation of infrared laser desorbed molecules. Biexponential decay of the delayed ion signal indicates the autoionization of two kinetically distinct superexcited states. The lifetimes of these states were determined to be 5 ± 1 μs and 0·8 ± 0·2 μs; their excitation energies are estimated to lie in the range 20–30 eV. These results are compared with the predictions of the Richardson-Dushman and Klots models of thermionic emission. The observation of a dependence of delayed ion intensity on desorption conditions is interpreted in terms of a thermally induced phase change during the desorption process.

ISSN:0026-8976    

DOI:10.1080/00268979300102471

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Our earlier work on non-singular effective polarizability and optical activity operators is generalized to remove the condition of well defined time reversal and Hermiticity characteristics of the optical activity operators. This enables depolarized right-angle incident (ICP) and scatteredcircularpolarization (SCP) and polarized right-angle incident (ILP) and scatteredlinearpolarization (SLP) Raman optical activity (ROA) observables to be formulated in terms of matrix elements of the absorptive and dispersive parts of these scattering operators. Stokes ICP and anti-Stokes SCP, and Stokes ILP and anti-Stokes SLP ROA observables are then shown quite generally to be related by thesameandoppositesign, respectively, for scattering from diamagnetic chiral molecules randomly oriented in an optically isotropic phase.

ISSN:0026-8976    

DOI:10.1080/00268979300102481

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In this paper it is shown that with EPR the polytype structure of K3Co(CN)6single crystals doped with Fe(CN)3-6, can be determined easily. The number of resonance lines for an arbitrary orientation of the magnetic field is indicative of the type of crystal studied. This is substantiated by the known crystallographic data concerning K3Co(CN)6.

ISSN:0026-8976    

DOI:10.1080/00268979300102491

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The effects of nuclear relaxation and change in vibrational molecular energy are accounted for in the theoretical determination of the molecular properties of HF, CH4, and C2H4. A method based on a finite-difference technique is employed. An analysis of the influence of these contributions versus the purely electronic contribution is made, together with an appraisal of the effect of vibrational excitation.

ISSN:0026-8976    

DOI:10.1080/00268979300102501

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor