Theoretical study of the photoionization shape resonances of cobaltocene and nickelocene

Photoionization cross section and angular distribution calculations of carbon tetrafluoride

Correlation in the photoionization dynamics of carbon tetrafluoride is studied in the framework of the time-dependent density-functional theory (TDDFT) approach by employing a multicentric basis set expansion of the scattering wave function linear combination of atomic orbitals (LCAO) TDDFT. Results obtained with the statistical average of orbital potentials and LB94 exchange-correlation (xc) potentials are compared with photoabsorption, photoionization, and electron-scattering experiments as well as with past theoretical calculations. Inadequacies in both the V(xc) parametrizations employed have been suggested from the analysis of the intensity plots for the D2A1 ionization. The formation of resonant scattering states in selected continuum channels has been studied through the analysis of the dipole-prepared scattering wave function; our findings are then compared with results of electron-scattering calculations. Overall, the LCAO-TDDFT results highlight the effectiveness of the approach for the calculation of the unbound spectrum of fairly large molecules.

Time dependent density functional study of the photoionization dynamics of SF6

The B-spline linear combination of atomic orbitals method has been employed to study the valence and core photoionization dynamics of SF6. The cross section and asymmetry parameter profiles calculated at the time dependent density functional theory level have been found to be in fairly nice agreement with the experimental data, with the quality of the exchange-correlation statistical average of orbital potential results superior to the Van Leeuwen-Baerends 94 (LB94) ones [Phys. Rev. A 49, 2421 (1994)]. The role of response effects has been identified by a comparison of the time dependent density functional theory results with the Kohn-Sham ones interchannel coupling effects and autoionization resonances play an important role at low kinetic energies. Prominent shape resonances features have been analyzed in terms of "dipole prepared" continuum orbitals and interpreted as due to a large angular momentum centrifugal barrier as well as anisotropic (nonspherical) molecular effective potential. Finally, the method has been proven numerically stable, robust, and efficient, thanks to a noniterative implementation of the time dependent density functional theory equations and suitability of the multicentric B-spline basis set to describe continuum states from outer valence to deep core states.

Theoretical study on the circular dichroism in core and valence photoelectron angular distributions of camphor enantiomers

In the present work the photoelectron circular dichroism of camphor has been theoretically studied using B-spline and continuum multiple scattering-Xalpha methods, and comparisons are made with available experimental data. In general, rather large dichroism effects have been found for both valence and core (O 1s, C 1s) photoionizations. The agreement between the two calculations reported here and previous experimental measurements for core C 1s data is essentially quantitative. For valence ionization satisfactory agreement between theory and experiment has been obtained and the discrepancies have been attributed to both exchange-correlation potential limitations and the absence of response effects in the adopted formalism. The calculations predict, moreover, important features in the cross-section profiles, which have been discussed in terms of dipole-prepared continuum orbitals.

Branching ratio deviations from statistical behavior in core photoionization

Accurate calculations of carbon 1s photoionization cross sections have been performed at the density functional level with the B-spline linear combination of atomic orbitals approach. The molecules considered are FC[triple bond]CH, FC[triple bond]CCH3, FC[triple bond]CCN, F2C=CH2, CF3COOCH2CH3, and C3H5O. The variation of the branching ratios relative to inequivalent C 1s ionizations have been evaluated from threshold to about 100 eV photoelectron kinetic energy. Large deviations from the statistical ratios are observed at low energies, which remain often significant several tens of eV above threshold. The importance of taking into account core branching ratios for peak deconvolution and quantitative analysis, as well as an additional tool for structural information, is pointed out. Strong shape resonant effects are found to largely cancel in branching ratios. Their nature and variation along the series is analyzed in the framework of excitations into sigma* valence orbitals.