Spectra of Ni- and Co-like ions of Xe in an electron-beam ion trap

High-resolution soft X-ray observations of Ni- and Co-like Xe ions in an electron-beam ion trap are compared with the predictions of various calculations. Calculated energy levels up to the 4p levels are presented alongside experimental determinations. PACS Nos.: 32.30.Rj; 34.50.Fa; 34.80.Dp

Extreme-ultraviolet wavelength and lifetime measurements in highly ionized krypton

We have studied the spectrum of highly ionized krypton in the extreme-ultraviolet wavelength region (50–300 Å), using beam-foil excitation of fast krypton ions at the Argonne ATLAS accelerator facility. We report measurements of transition wavelengths and excited-state lifetimes for n = 2 states in the lithiumlike, berylliumlike, and boronlike ions, Kr31+,32+,33+. Excited state lifetimes ranging from 10 ps to 3 ns were measured by acquiring time-of-flight-delayed spectra with a position-sensitive multichannel detector.PACS Nos.: 32.70.Cs, 32.30.Jc, 34.50.Fa

Analysis of electron-atom collision processes involving strong coupling

Inelastic electron – sodium atom collisions are investigated in the two-channel approximation. The scattering potentials are calculated using hydrogen-like wave functions for the valence electron of sodium. The coupled differential equations governing the collision process are solved using the Numerov numerical technique. The results thus obtained are in good agreement with those obtained by other sophisticated models. PACS Nos.: 34.50.Fa, 34.80.Dp

Near-threshold ionization of atoms and molecules by positron impact

Distorted-wave models previously used to study the ionization of hydrogen and the noble gases by positron impact at medium kinetic energies are employed to produce cross sections for impact energies within 0.02 eV of the ionization threshold. These theoretical cross sections are compared with the Wannier–Klar threshold power-law formula and the existing experimental results. PACS Nos.: 34.50.Fa, 34.85.+x

Electron impact ionization of the ground state of singly ionized helium

We calculate the total and single differential cross sections for the electron impact ionization of the ground state of singly ionized helium at various energies in a distorted wave approximation. Present results are compared with existing theoretical and experimental results. PACS Nos.: 34.80.Dp, 34.50.Fa

Heavy-ion storage ring measurement of forbidden transition rates between ground-configuration levels in Si6+ and Si8+ ions

The decay by magnetic dipole and electric quadrupole (M1 and E2) transitions of the 2s22p2 1D2 level in the ground complex of the C-like ion Si8+ and the 2s22p4 1D2 level in the O-like ion Si6+ have been optically observed with ions circulating in a storage ring. The measured natural level lifetimes of (38.3 ± 0.3) ms for Si8+ and (636 ± 0.7) ms for Si6+ corroborate theoretical data for such forbidden decays in multicharged ions of astrophysical interest. PACS Nos.: 32.70.Cs, 32.30.Jc, 34.50.Fa