Atomic-number dependence of the magnetic-sublevel population in the autoionization state formed in dielectronic recombination

Abstract

The magnetic-sublevel population of the autoionization state formed in dielectronic recombination (DR) of highly charged heavy ions has been experimentally investigated by combining two types of measurements with an electron beam ion trap. The two different measurements are the differential x-ray measurement at ${90}^{\ensuremath{\circ}}$ with respect to the electron beam and the integral resonance-strength measurement. The alignment parameter, which denotes the magnetic-sublevel population distribution, has been obtained for the autoionization states ${[1s2{s}^{2}2{p}_{1/2}]}_{1}$ formed in DR of Li-like Pr (atomic number $Z=59$) and Ho ($Z=67$). This work is a complement to our previous work [Phys. Rev. Lett. 108, 073002 (2012)] on Li-like Au ($Z=79$). The experimental results are in reasonable agreement with theoretical predictions, and a strong $Z$-dependent tendency due to the Breit interaction has been confirmed.