5 p -4 f level crossing in palladium-like ions and its effect on metastable states
We study the level structures of palladium-like I7 + (Z =53 ) and Ba10 + (Z =56 ) and the behavior of their metastable states with an electron beam ion trap. The difference in the level structures between I7 + and Ba10 + arising from the configuration crossing between 4 d-15 p and 4 d-14 f around the atomic number Z = 56 causes significant differences in the lifetimes of the metastable states. Ba10 + has several long-lived levels (>10-3 s ) in the electron configurations 4 d-15 s and 4 d-14 f , whereas the lifetime of the same 4 d-14 f levels in I7 + is much shorter due to the appearance of deexcitation channels to a lower energy level in 4 d-15 p . The extreme ultraviolet spectra identified through comparison with theoretical simulations based on a collisional-radiative model evince the level crossing between the 4 d-15 p and 4 d-14 f configurations in Ba10 +. Additionally, we investigate the ionization processes from the metastable states in palladium-like ions by observing the electron energy dependence of the prominent visible line (4 d-1:2D5 /2-2D3 /2) of rhodium-like I8 + and Ba11 +. The electron energy dependencies reflecting the properties of the metastable states show a difference between iodine and barium, which can be explained by the populations of the metastable states calculated with theoretical simulations.
Physical Review A
- Pub Date:
- September 2020