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  • 1
    Electronic Resource
    Electronic Resource
    Electronic excitation and ionization spectra of cyclopentadiene: Revisit by the symmetry-adapted cluster–configuration interaction method (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 5245-5252 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Electronic excitation and ionization spectra of cyclopentadiene (CP) were reinvestigated by the symmetry-adapted cluster (SAC) and SAC–configuration interaction (SAC-CI) method with an extended basis set and a wide active orbital space. To give a satisfactory interpretation of the general profile of the observed excitation spectrum, 40 low-lying excited singlet and triplet states (with excitation energies of up to 9.5 eV) were computed. The calculated excitation energies were greatly improved compared to those reported previously. All of the peaks in the experimental spectrum were reassigned theoretically with small deviations. The natures of the low-lying valence and Rydberg-excited states were discussed in detail, and the results were also compared with those of some other recent theoretical studies. The ionization energies calculated by the SAC-CI general-R method agree well with the experimental peaks in the photoelectron spectrum. A number of two-electron shake-up states were calculated below 23 eV. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1290004
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  • 2
    Electronic Resource
    Electronic Resource
    Excited and ionized states of free base porphin studied by the symmetry adapted cluster-configuration interaction (SAC-CI) method (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 2321-2329 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The SAC(symmetry adapted cluster)/SAC-CI method is applied to the calculations of the ground, excited, and ionized states of the free base porphin. The electronic spectrum of porphin is well reproduced and new assignments for the B (Soret), N, L, and M bands are proposed. The present result shows that the four-orbital model is strongly perturbed for the B and N bands by the excitations from the lower 4b1u MO and that the σ electron correlations are important for the description of the excited states. The absorption peaks in the ionization spectrum are assigned and the reorganization effect is found to be large especially for the n and σ electron ionizations. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470927
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  • 3
    Electronic Resource
    Electronic Resource
    Theoretical study on the ground and excited states of the chromate anion CrO2−4 (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 1029-1036 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The symmetry adapted cluster (SAC) and SAC-configuration interaction (SAC-CI) theories are applied to the calculations of the ground and excited states of the chromate ion CrO2−4. Electron correlations are very large for this molecule and work to relax the charge polarization of the Cr–O bonds in the ground state. The experimental spectrum of CrO2−4 is well reproduced by the present calculations, which is the first ab initio study of the excited states including electron correlations. All of the observed peaks are assigned to the dipole allowed transitions to the 1T2 excited states. Furthermore, many kinds of forbidden transitions are calculated in the lower energy region. Both allowed and forbidden transitions are characterized as the electron-transfer excitations from oxygen to metal. In comparison with the previous theoretical studies, the present SAC-CI results are in good agreement with experiment and give reliable assignments of the spectrum. We also compare the electronic structures and spectra of CrO2−4, MoO2−4, MnO−4, RuO4, and OsO4, which have been studied by the SAC and SAC-CI methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467801
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  • 4
    Electronic Resource
    Electronic Resource
    Excited and ionized states of aniline: Symmetry adapted cluster configuration interaction theoretical study (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 117 (2002), S. 2045-2052 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Singlet excited states and ionized states of aniline are studied by the symmetry adapted cluster/configuration interaction method. Absorption bands of states that have mainly π–π* nature are assigned as 1A″ (∼1B2), 1A′ (∼1A1), 1A″ (∼1B2), 1A′ (∼1A1), 1A″ (∼1B2) in increasing-energy order. An s-Rydberg state is predicted to lie between the first and second valence states, in agreement with recent experimental results. The lowest band has a charge-resonance character with a slight charge-transfer (CT) character (CT is defined as NH2→C6H5); third and fifth valence bands have back-CT (BCT) nature, and second and fourth are local excitations within the benzene ring. The extent of CT of excited states depends on amino group conformation. In the planar form, CT characters of several states were altered; however, spectral shapes are very similar to that of the equilibrium form. On the other hand, amino group twisting altered both the spectrum and nature of excited states. Third and fourth lowest valence states exhibited strong CT character, while fifth to eighth states are of the strong BCT type, implying that the CT nature of excited states of aniline can be changed by amino group twisting. For ionized states, the lowest three states are assigned to 2A′ (∼2B1), 2A″ (∼2A2), 2A′ (∼2B1) in increasing-energy order, all being π-ionizations. The sixth one is also due to π-ionization (∼2B1) and the others are σ-ionizations. Ordering was the same as Koopmans' case. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1487827
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  • 5
    Electronic Resource
    Electronic Resource
    Electronic excitation and ionization spectra of azabenzenes: Pyridine revisited by the symmetry-adapted cluster configuration interaction method (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 5117-5123 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Electronic excited and ionized states of pyridine were reinvestigated by the symmetry-adapted cluster configuration interaction (SAC-CI) method using an extended basis set and a wide active space. The present SAC-CI results for the singlet and triplet excited states are greatly improved and agree well with the experimental observations, providing a firm assignment of all low-lying n→π* and π→π* valence excited states observed in the vacuum ultraviolet spectrum and electron energy-loss spectrum. The ionization potentials were reexamined by the SAC-CI general-R (R represents excitation operator) method. The first four ionization potentials are greatly improved compared with our previous results obtained by the SAC-CI single- and double-R (SD-R) method. The present theoretical ionization potentials are in good agreement with the experimental values in high-resolution synchrotron photoelectron spectrum for energy regions up to 25 eV (which contain outer- and inner-valence regions), and give a detailed theoretical assignment for the photoelectron spectra. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1351880
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  • 6
    Electronic Resource
    Electronic Resource
    Electronic excitation spectrum of thiophene studied by symmetry-adapted cluster configuration interaction method (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 842-850 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Electronic excitation spectrum of thiophene was investigated by the symmetry-adapted cluster (SAC)/SAC configuration interaction method. Seventy singlet and four lowest triplet electronic states of thiophene were computed to give a detailed satisfactory theoretical interpretation of the vacuum ultraviolet (VUV) spectrum and the electron energy loss spectrum of thiophene. The present calculations gave the 2 1A1 valence state at 5.41 eV and the 1 1B2 valence state at 5.72 eV with oscillator strengths 0.0911 and 0.1131, respectively, and the 5 1A1 valence state at 7.32 eV and the 4 1B2 valence state at 7.40 eV with oscillator strengths 0.3614 and 0.1204, respectively. These valence-excited states were assigned to the two strong absorption bands of the VUV spectrum centered around 5.5 and 7.05 eV, respectively. A number of Rydberg transitions were obtained and assigned to the 6.0, 6.6, and 7.5–8.7 eV, etc. energy regions. The similarities and differences in the electronic excitations between thiophene and other five-membered ring compounds were discussed. The accuracy and assignment of the present results are compared with those of the recent theoretical studies by CASPT2 and multireference double configuration interaction methods. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1332118
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  • 7
    Electronic Resource
    Electronic Resource
    Theoretical Study on the Reaction Mechanism and Regioselectivity of Silastannation of Acetylenes with a Palladium Catalyst (1994)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 116 (1994), S. 8754-8765 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00098a038
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  • 8
    Electronic Resource
    Electronic Resource
    Electronic excitation spectra of furan and pyrrole: Revisited by the symmetry adapted cluster–configuration interaction method (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 7853-7866 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Electronic excitation spectra of furan and pyrrole are reinvestigated by the symmetry-adapted cluster configuration-interaction method. The 47 and 46 lowest singlet and triplet electronic states are computed for furan and pyrrole, respectively. Two series (1a2 and 2b1) of low-lying Rydberg states and the valence π–π* excited states strongly influence each other in both furan and pyrrole. The present calculations give detailed and satisfactory theoretical assignments of the vacuum ultraviolet spectra and the electron energy-loss spectra of the two molecules. The similarities and differences in the electronic excitations between furan and pyrrole are discussed in detail. The accuracy and assignments of recent theoretical studies, i.e., complete active space second-order perturbation, multireference Møller–Plesset perturbation, second-order algebraic-diagrammatic construction, multireference double configuration interaction, and CC3, are compared. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1316034
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