The contribution to electron-impact ionization cross sections from excitations to high-nl shells and a consequent autoionization is investigated. We perform relativistic subconfiguration-average and detailed level-to-level calculations for this process. Ionization cross sections for the W27+ ion are presented to illustrate the large influence of the high shells (n ^ 9) and orbitals (/ > 4) in the excitation-autoionization process. The obtained results show that the excitations to the high shells (n ^ 9) increase cross sections of the indirect ionization process by a factor of 2 compared to the excitations to the lower shells (n < 8). The excitations to the shells with orbital quantum number l = 4 give the largest contribution compared with the other orbital quantum numbers /. Radiative damping reduces the cross sections of the indirect process approximately twofold in the case of the level-to-level calculations. Determined data show that the excitation-autoionization process contributes approximately 40 % to the total ionization cross sections.

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It is shown that excitations from the ground configuration to high-nl shells of the W 26+ ion have a large contribution to the electron-impact ionization process. Large-scale calculations for the excitations to over 900 configurations are performed using the Dirac-Fock-Slater approximation. The investigation includes subconfiguration-average and detailed level-to-level approaches. Our findings illustrate how important it is to study convergence of cross sections for the excitations to the high-nl shells. The obtained results show that the excitations from the 4s, 4p, and 4d shells to the shells with the orbital quantum number l = 4 dominate in the indirect process of the ionization. The excitation-autoionization cross sections make about 40% of the total ionization cross sections. Comparison between our data and previous configuration-average distorted-wave calculations for Maxwellian rate coefficients reveals large discrepancies for the direct and indirect parts of the ionization process.

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We present the experimental and theoretical study of correlation effects in epitaxial SrRuO 3 thin films. Experimentally, we have performed resonant ultraviolet photoemission spectroscopy (UPS) and angle-resolved hard x-ray photoemission spectroscopy (HAXPES) measurements. For resonant UPS, the two methods, Fanoprofile fitting of constant initial state spectra and the energy distribution curves equidistant difference spectra, were used to extract Ru 4d partial spectral weight (PSW) in the valence band. We find Ru 4d PSW possessing a clearly pronounced coherent peak at the Fermi level together with angle-resolved HAXPES spectra demonstrating no difference in surface and bulk electronic structure. From comparison of experimental data with theoretical calculations done at density functional theory level, we conclude that SrRuO 3 is a weakly correlated material and electronic structure of it can be consistently described employing first-principles approaches.

We present a first-principles investigation of structural and elastic properties of experimentally observed phases of bulk SrRuO3 - namely orthorhombic, tetragonal, and cubic - by applying density functional theory (DFT) approximations. First, we focus our attention on the accuracy of calculated lattice constants in order to find out DFT approaches that best represent the crystalline structure of SrRuO3, since many important physical quantities crucially depend on change in volume. Next, we evaluate single-crystal elastic constants, macroscopic elastic parameters, and mechanical stability trying to at least partially compensate for the existing lack of information about these fundamental features of SrRuO3. Finally, we analyze the anomalous behavior of low-temperature orthorhombic phase under C44 related shear deformation. It turns out that at critical strain values the system exhibits a distinct deviation from the initial behavior which results in an isosymmetric phase transition. Moreover, under C44 related shear deformation tetragonal SrRuO3 becomes mechanically unstable raising an open question of what makes it experimentally observable at high temperatures.

The radiative and Auger cascades following the creation of the 2s shell vacancy in the Fe2+ ion are investigated by performing level-to-level calculations. The branching ratios of the cascades are analyzed and the main decay mechanisms are identified for all levels of the Fe3+ 2s 3d6 configuration. The study shows that the Fe5+ ion is mainly populated in the cascade process. It is demonstrated that the ion yield strongly depends on the level of the initial configuration. The ion yield is presented for all levels of the Fe3+ 2s 3d6 configuration. A study of the time dependence of the population for configurations obtained in cascades shows that it takes ∼10−15 s to reach configurations of the Fe6+ ion. We demonstrate that previous calculations for the decay of the 2s shell vacancy produced in Fe2+ provide an overestimated ion yield for higher ionization stages.

Electron-impact ionization cross sections for the ground level of the W25+ ion have been investigated by performing level-to-level calculations and using the Dirac–Fock–Slater method in the single-configuration approach. The main attention has been focused on the influence of the increasing principal and orbital quantum numbers on the excitation-autoionization (EA) process and its contribution to the total ionization cross sections. The obtained results demonstrate that excitations to the high-nl shells ( ) increase cross sections of the indirect ionization process by about 60% compared to the excitations to the lower shells ( ). It was established that excitations to the shells with the orbital quantum number l = 4 give the greatest contribution to EA. Maxwellian rate coefficients derived from the cross sections for the ground state are compared with the previously obtained values from the configuration-average distorted-wave (CADW) approximation. The rate coefficients for direct ionization (DI) are smaller than the corresponding CADW values, while the EA rate coefficients are larger than the ones from the CADW calculations. The total DI+EA rate coefficients are about 20% larger than the CADW rate coefficients.