  We theoretically study orbital alignment in x-ray-ionized atoms and ions,
based on improved electronic-structure calculations starting from the
Hartree-Fock-Slater model. We employ first-order many-body perturbation theory
to improve the Hartree-Fock-Slater calculations and show that the use of
first-order-corrected energies yields significantly better transition energies
than originally obtained. The improved electronic-structure calculations enable
us also to compute individual state-to-state cross sections and transition
rates and, thus, to investigate orbital alignment induced by linearly polarized
x rays. To explore the orbital alignment of transiently formed ions after
photoionization, we discuss alignment parameters and ratios of individual
state-resolved photoionization cross sections for initially neutral argon and
two exotic electronic configurations that may be formed during x-ray
multiphoton ionization dynamics induced by x-ray free-electron lasers. We also
present how the orbital alignment is affected by Auger-Meitner decay and
demonstrate how it evolves during a sequence of one photoionization and one
Auger-Meitner decay. Our present work establishes a step toward investigation
of orbital alignment in atomic ionization driven by high-intensity x rays.
