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71.
A simple vibronic coupling model involving two electronic states and two vibrational modes is considered. The model is based on harmonic diabatic potentials and linear coupling of the diabatic electronic states. It is shown that the adiabatic electronic potential energy surfaces exhibit, in general, a conical intersection. The well known E × E and E × B Jahn-Teller problems are contained as special cases. Using numerical methods the optical absorption spectrum is calculated exactly. Extremely complex vibronic spectra are obtained when the conical intersection occurs within the Franck-Condon (FC) zone. The exact vibronic spectra are compared with spectra calculated in the adiabatic and FC approximation. The genuine spectroscopic effects of conical intersections are revealed by a comparison with the results of standard one-dimensional vibronic coupling calculations. The presence of a conical intersection limits the applicability of the adiabatic and FC approximations much more strongly than in the one-dimensional case. The upper adiabatic electronic state is strongly affected by non-adiabatic coupling even when the point of intersection lies outside the FC zone. The relevance of these results for the calculation of molecular electronic spectra is briefly discussed. 相似文献
72.
Mixtures of cold bosonic atoms in optical lattices undergo demixing on different length scales with increasing interspecies repulsion. As a general rule, the stronger the intraspecies interactions, the shorter is this length scale. The wealth of phenomena is documented by illustrative examples on both superfluids and Mott insulators. 相似文献
73.
B. Kellerer L.S. Cederbaum G. Hohlneicher 《Journal of Electron Spectroscopy and Related Phenomena》1974,3(2):107-122
A theory recently developed1–6 for the direct calculation of Koopmans' defect—the difference between the vertical ionization potential and the value obtained by application of Koopmans' theorem7—is combined with semiempirical molecular orbital methods like CNDO/28. It is shown that even using these wavefunctions good results are obtained. Especially well predicted in all cases treated is the ordering between experimental ionizations and orbitals. 相似文献
74.
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76.
It is shown that for highly symmetric molecules the ionization of a core electron leads quite generally to a lowering of the symmetry. The breaking of the symmetry is a consequence of the vibronic coupling between nearly degenerate core orbitals of different symmetry. The vibronic coupling leads to strong excitation of non-totally symmetric vibrational modes in addition to the usually observed excitation of totally symmetric modes. As an example, the vibrational structure of the Ols line of the CO2 molecule is computed on the one-particle level. 相似文献
77.
The ionization potentials of SF6 are studied by an ab initio many-body approach which includes the effects of electron correlation and reorganization beyond the one-particle approximation. The ordering of the ionization potentials in the energy range of the HeII line obtained in the SCF approximation is 1t1g 5t1u, 3eg + 1t2u, 1t2g, 4t1u, 5a1g (the “+” sign denotes nearly equal ionization potentials), whereas in the many-body calculation it is 1t1g, 5t1u + 1t2u, 3eg, 1t2g, 4t1u, 5a1g. The second band in the photoelectron spectrum thus corresponds to two ionization potentials and the third one to only one. 相似文献
78.
Cyclic carbon cluster dianions (CC(2))(2-)(n)(n = 3-6) are investigated by ab initio methods with regard to their geometric properties, electronic stability, and aromaticity. The unique wheel-like structures of these dianions consist of a n-membered carbon ring, where a C(2) unit is attached to each carbon atom. All investigated dianions represent stable gas-phase dianions. While the smallest member of this family (CC(2))(2-)(3) is clearly aromatic, the aromatic character decreases rapidly with increasing ring size. The geometries and the aromaticity of the cyclic clusters (CC(2))(2-)(n)(n = 3-6) can be nicely explained using resonance structure arguments. 相似文献
79.
Markmann A Worth GA Mahapatra S Meyer HD Köppel H Cederbaum LS 《The Journal of chemical physics》2005,123(20):204310
Using a five-state, all-mode vibronic coupling model Hamiltonian derived in a previous publication [A. Markmann et al., J. Chem. Phys. 122, 144320 (2005)], we have calculated the photoelectron spectrum of the pentatetraene cation in the neighborhood of the B (2)E state, which can be represented with charge-localized components. To this end, quantum nuclear dynamics calculations were performed using the multiconfiguration time-dependent Hartree method, taking all 21 vibrational normal modes into account. Compared to experiment, the main features are reproduced but higher accuracy experiments are necessary to gauge the accuracy of the predictions for the vibronic progressions at the rising flank of the spectrum. 相似文献
80.
The vertical valence ionization potentials of trans-N2F2 and cis-N2F2 have been computed by a many-body Green function method. For trans-N2F2 the agreement with experiment is very satisfactory in general and the calculations permit an analysis and assignment of the experimental photoelectron spectrum. The ionization potentials of cis-N2F2 are predictions. The ordering of the ionization potential is for trans-N2F2 5ag(n+), 2au(π), 4bu(n?), 4ag, 1bg(π), 1au(π), 3bu, 3ag, 2bu and for cis-N2F2 4b2 (n?), 2b1 (π) + 5a1(n+), 3b2, 1a2 (π), 1b1(π), 4a1, 3a1, 2b2, n+ and n? denote lone pairs on the N atoms except for the 4bu(n?) orbital which has the largest contribution from the F atoms. 相似文献