X-ray observations of 2l-nl' transitions from Zr, Nb, Mo, and Pd in near-neonlike charge states.

Abstract

X-ray spectra of 2l-nl\ensuremath{'} transitions with 3\ensuremath{\le}n\ensuremath{\le}12 in the row-5 transition metals zirconium (Z=40), niobium (Z=41), molybdenum (Z=42), and palladium (Z=46) from charge states around neonlike have been observed from Alcator C-Mod plasmas. Accurate wavelengths (\ifmmode\pm\else\textpm\fi{}0.2 m\AA{}) have been determined by comparison with neighboring argon, chlorine, and sulfur lines with well-known wavelengths. Line identifications have been made by comparison to ab initio atomic structure calculations, using a fully relativistic, parametric potential code. For neonlike ions, calculated wavelengths and oscillator strengths are presented for 2p-nd transitions with n between 3 and 12. The magnitude of the configuration interaction between the (2${\mathit{p}}^{5}$${)}_{1/2}$6${\mathit{d}}_{3/2}$ J=1 level and the (2${\mathit{p}}^{5}$${)}_{3/2}$7${\mathit{d}}_{5/2}$ J=1 levels has been measured as a function of energy-level spacing for successive-atomic-number neonlike ions, and the agreement with theory is good. Transitions in the 2${\mathit{p}}_{1/2}$-${\mathit{nd}}_{3/2}$ series in neonlike ${\mathrm{Mo}}^{32+}$ with n\ensuremath{\ge}13 are not observed; the upper levels lie above the first ionization potential of the neonlike ion and have a large branching ratio towards autoionization. Measured and calculated wavelengths and oscillator strengths of selected transitions in the aluminum-, magnesium-, sodium-, fluorine-, and oxygenlike isosequences are also presented. \textcopyright{} 1996 The American Physical Society.