# Radiative rates and electron impact excitation rates for transitions in He II

## TL;DR

This paper presents detailed calculations of atomic data such as energy levels, radiative rates, and collision strengths for He II, using advanced relativistic atomic structure and R-matrix methods, providing comprehensive data for astrophysical and laboratory plasma modeling.

## Contribution

The study provides new, extensive atomic data for He II, including energy levels, transition rates, and collision strengths, calculated with state-of-the-art relativistic methods, and compares them with previous results.

## Key findings

- Calculated energy levels and transition rates for He II.
- Provided collision strengths over a wide energy range.
- Assessed the accuracy of the data through comparisons.

## Abstract

We report calculations of energy levels, radiative rates, collision strengths, and effective collision strengths for transitions among the lowest 25 levels of the n <= 5 configurations of He~II. The general-purpose relativistic atomic structure package (GRASP) and Dirac atomic R-matrix code (DARC) are adopted for the calculations. Radiative rates, oscillator strengths, and line strengths are reported for all electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2) transitions among the 25 levels. Furthermore, collision strengths and effective collision strengths are listed for all 300 transitions among the above 25 levels over a wide energy (temperature) range up to 9 Ryd (10**5.4 K). Comparisons are made with earlier available results and the accuracy of the data is assessed.