Fukashi Sasaki

Abinitio SCF CI calculations on the ground and π–π* excited states of the pyrrole molecule and its positive ion

Ab initio SCF π‐electron CI calculations are carried out on the ground and lower π–π* excited states of pyrrole and its positive ion. The four singlet states found at 5.9, 6.8, 7.2, and 7.4 eV by experiment are tentatively assigned as the 1B2, 1A1, 1B2, and 1A1 states, respectively. The calculated excitation energies for these four states are 6.0, 6.5, 7.1, and 7.3 eV, respectively. The first excited 1A1 state is a valence type state, whereas the other three states are Rydberg type states. The lowest excited state found at 4.35 eV by experiment is assigned as the 3B2 state, whose calculated excitation energy is 4.27 eV. The three lowest excited states of the positive ion due to π‐electron ionization are also investigated. The calculated ionization potentials are 8.10 (2A2), 8.94 (2B1), and 13.33 eV (2B1). They are in good agreement with experimental values of 8.21, 9.20, and 13.0 eV. The lowest two states are represented by la2→∞ and 2b1 →∞, respectively, whereas the second 2B1 state is a mixture of three...

APPLICATION OF PAIR CORRELATION THEORY TO POSITRONIUM COMPOUNDS

Extension of weak orthogonality (WO) techniques developed by Szalewicz et al. and coupled pair equations derived by Jeziorski et al. to positronium compounds are presented. These methods enable us to calculate many‐electronic positronium compounds with explicitly correlated functions. These methods were applied to positronium hydride (PsH) with Hylleraas‐type functions (HTF’s), and the total energies, the positron‐electron two‐photon annihilation rates, and the positronium binding energies were calculated. Extended coupled pair equations were solved by CEPA(2)‐type, complete coupled pair (CCP) procedures, and independent pair approximation (IPA) of CCP. For the total energies, IPA, CEPA(2), and CCP procedures gave −0.78899, −0.78238, and −0.77471 au, respectively. For the two‐photon annihilation rates, the respective procedure gave 2.088, 2.064, and 1.972 ns−1, respectively.

Ab initio potential energy curves for the CO+ ion and a study of the photoelectron spectra of CO

The potential energy curves for the low-lying electronic states of CO+ are calculated by using the ab initio full valence configuration interaction method with minimal STOs. Calculated spectroscopic parameters are given for twenty five bound states, and the compared with the experimental values for four observed bound states. The band systems, observed in the 22 eV and 27 eV region of He II photoelectron spectra of CO, are analysed by using calculated potential energy curves and spectral intensities. New assignment for the fourth band system at 22 eV ∼ 23 eV is proposed.

Potential curves of the ground state and low-lying states of the scandium dimer using state-averaged MCSCF orbitals

Abstract Global potential curves have been obtained for the ground state and low-lying states of the Sc dimer with state averaged complete active space self-consistent field and multireference configuration interaction calculations. The obtained curves are smooth over a wide range of internuclear distances. The calculated spectroscopic constants of the ground state agree well with experiment. The configurations arising from the 4 F + 4 F atomic limit become predominant in the bonding region for the second and third states.

Theoretical study of the satellite bands in the valence shell XPS spectra of N2, CO, O2 and NO molecules☆

Abstract The energies for the ionized states of N 2 , CO, O 2 and NO are obtained by using an ab initio full valence configuration interaction. (FVCI) method with a minimal basis set. The intensities of the corresponding valence shell MgKα X-ray photoelectron spectroscopy (MgKα-XPS) spectra are estimated with plane wave approximation and the satellite bands in the observed spectra are analyzed. The present FVCI results give a quite reasonable interpretation of the bands, both with regard to the positions and the relative intensities. New assignments are proposed for some bands Of O 2 and NO.

POTENTIAL ENERGY CURVE OF THE GROUND STATE OF THE TITANIUM DIMER

Abstract A global potential energy curve has been obtained for the ground state of the Ti dimer with state averaged complete-active-space self-consistent-field (CASSCF) and multi-reference (MR) configuration interaction (CI) calculations. The calculated potential curves have a large barrier at intermediate internuclear distances (R). The dissociation energy of the ground state was estimated and is in agreement with an experimental estimate.

Theoretical study of the resonance state in the photodetachment of

Photodetachment cross sections were calculated for the state of by using the R-matrix method. Three channels, , and were taken into account. The resultant cross sections were compared with the experiments and other theoretical calculations. We found that the peak for the resonance state is located at 6.93 eV. Assuming the resonance formula given by Fano, a resonance energy of 6.6 eV and width of 1.4 eV were obtained.

NEW LOCALIZED ORBITALS APPROPRIATE FOR POST-HARTREE-FOCK CALCULATIONS

In this work, we propose a new orbital set based on density matrices of subsystems. Most of the resultant orbitals are localized in the subsystems and resemble the natural orbitals of the subsystems. Correlation between two electrons, each in a distant localized orbital, should be small and the corresponding configurations can be neglected in a calculation. Test calculations are performed on hexatriene and the usefulness of these orbitals is shown.

A data-oriented CI program system

A program system has been developed for calculation of molecular electronic structure using the configuration interaction (CI) method. Emphasis is placed on the inherent genealogical data structure of the files which a program system produces. Based on this genealogy, a language is provided for users which allows easy and consistent manipulation of files in the new system. Users need only specify a file which contains the desired data, using this file manipulation language. If the desired file does not exist, the new system creates it automatically by calling appropriate modules. The new system may be regarded as a data base equipped with computational ability.

Theoretical determination of energies and widths of autoionizing states of the Be atom

The energy and width of the autoionizing state of the Be atom were calculated. A series of multireference configuration-interaction (MRCI) calculations with an extensive Slater-type function (STF) basis set was carried out and the full CI energy was estimated for each of the neutral and ionized states. The estimated energy of is with respect to the ionized state. The photoionization cross section from the state was calculated by using the R-matrix method. The resultant energy and width are and , respectively, in reasonable agreement with the observed values of and . The energies and widths of the series up to n = 11 were also calculated.