Fumihiro Koike

4D PHOTOIONIZATION OF SINGLY-CHARGED XE, BA, AND EU IONS

Using a photon-ion merged-beam apparatus, the relative photoion-yield spectra for doubly- and triply-charged ions from Xe+, Ba+ and Eu+ ions were measured in the 4d ionization region. The giant resonance peak appears for all target ions. The peak of Xe+ is broad and that of Eu+ is relatively narrow, similar to those observed in the neutral atoms. The spectrum of Xe3+ shows some structures around 87 and 93 eV. The summit of the giant resonance peak of Eu2+ is obviously split into two. These structures observed in the Xe3+ and Eu2+ spectra are not observed in the photoion spectra of the neutral targets. Some small peaks are observed in the Xe+ spectrum between 70 and 76 eV. A multi-configuration Dirac-Fock calculation reveals that these peaks are attributed to 4d-np and 4d-nf transitions. It was also found that the broad peak centered at 100 eV corresponds to shake-up resonance (4d105s25p5→4d94f5s25p4np [n=6.7]) processes. Some prominent peaks that do not appear in the neutral Ba spectrum are observed clearly in the Ba+ one. These peaks are most probably due to the 4d-nf transition followed by Auger processes.

MCDF calculations for EUV-emissions of 4d-open shell ions based on the features of non-local exchange integrals

Wavelengths and intensities of extreme ultra-violet optical emissions are studied for 4d – 5p transitions of Xe10+ions in plasmas. The electronic states of the ions have been calculated employing a method based on the multi-con.guration Dirac-Fock approximation. Dipole transition rates have been calculated allowing the non-orthogonal orbital wavefunctions between the initial and final electronic states. Single and double electron virtual excitations have been taken into account to evaluate the electron correlations. The orbital relaxations and electron correlations have substantial effects on the formation of the transition arrays.

Many electron correlations and dynamics in atoms and multi-charged atomic ions

Electron correlations in atoms or atomic ions with multiple electrons are discussed extensively. The scheme of correlations between the electronic configurations are investigated in view of the (Dirac)-Hartree-Fock type variational calculations. In highly lying states realized by multiple inner-shell electron excitations, single electron orbitals have to be modified in accordance with the creation of electron vacancies near the atomic centre; the optimizatons of orbitals for individual energy levels are indispensable to gain a good insight of such atomic states and their dynamics. Electronic configurations with the same total parities may interact each other even in the cases that the constituent single electron orbitals have opposit parities. Such configuration interactions may induce the hybridization of single electron orbitals providing us with characteristic interference structures in the optical emission or absorption spectra. Numerical examples have been illustrated for several atomic or ionic systems such as lithium hollow atomic states, neon core excited states, and 4d-open highly charged tin ionic states.

Photoabsorption and subsequent decay of Na and Mg atoms in the 2s–np autoionizing resonance region

Photoabsorption and subsequent decay of Na and Mg atoms have been studied experimentally in the vicinity of the 2s excitation region. The charge-separated photoion-yield method using monochromatized synchrotron radiation was employed to detect the resonance excitation features separately in the single and double ionization channels. The photoion-yield spectrum of each atomic species consists of asymmetric features from the 2s−1np autoionizing resonance series below the 2s ionization limit and several weak features from the 2s−13s−1npns shake-up processes above the ionization limit. The observed resonances were analysed by multi-configuration Dirac–Fock calculation and by least-squares fitting to the Beutler–Fano profile. The decay processes of the resonance states are discussed. The Na 2s−13p resonance can end up with Na2+ ions by one-step double autoionization with branching ratio about 0.05.

Excitation and decay dynamics of 1s2s inner-shell double-vacancy states of neon atoms

The photo-excitation and Auger decay processes of inner-shell double vacancy states 1s2s2p6(1,3S)3s3p of neutral neon atoms have been studied theoretically. Multi-configuration Dirac-Fock (MCDF) calculations have been carried out, with electron correlation effects taken into consideration. The relaxation of core and excited orbitals and configuration interaction are found to be crucial to creating the double vacancy states by single photo-absorption. The predominant decay paths for the double vacancy states turn out to be of the LLM Auger decay to 1s 2s22p53s(3p), KLL Auger decay to 1s22s2p43s3p, and KLM Auger decay to 1s22p63s(3p). They lead to further Auger decay, creating the neon ions of multiple charge states. For both double and single vacancy states the spectator type of Auger process is dominated in all the Auger decay processes. Theoretical Auger electron spectra are presented for further investigations, experimental and theoretical.

The RATIP program. Recent developments and extensions

During the past years, the RATIP program has been found useful for calculating a variety of atomic data, including level structures, transition probabilities, Auger parameters as well as a number of excitation, ionization and capture cross sections. Here, the recent extensions to the RATIP code are reviewed which help analyze and explain many experiments from atomic spectroscopy.