Results in Physics (Jun 2022)
Relativistic theoretical calculations of singly and doubly energy levels, lifetimes, wavelengths, weighted oscillator strengths and radiative rates for Helium-Like Ions with Z=5−9
Abstract
We provide accurate energy levels for the lowest singly excited 70 levels among 1snl(n≤6,l≤(n−1))configurations and the lowest doubly excited 250 levels arising from the K-vacancy 2ln′l′(n′≤6,l′≤(n′−1))configurations of helium-like ions with Z=5−9. Wavelengths, weighted oscillator strengths and transition rates for electric-multipole (dipole (E1), quadrupole (E2)) and magnetic-multipole (dipole (M1), quadrupole (M2)) are also calculated. The lifetimes determinations are reported for all the calculated levels. The calculations were performed using the Relativistic Configuration Interaction (RCI) method implemented in the Flexible Atomic Code (FAC). For comparative purposes, the second set of calculations was obtained with other packages of programs for relativistic atomic structure calculations (AMBiT) based on a method combining many-body perturbation theory and configuration interaction (CI). Additionally, the Breit interaction and leading quantum electrodynamics effects (QED) are included. Our results are compared with other available theories reported in the literature as well as the data taken from NIST online database. A good agreement between them has been found. We signal that our calculations for the doubly excited levels are made for the first time and they provide accurate and complete atomic data on these ions. Our results can contribute to the NIST database by essentially extending the data for doubly excited states.
