On the importance of satellite lines to the He-like K ALPHA complex and the G ratio for calcium, iron, and nickel

TL;DR

This paper presents detailed calculations of He-like K ALPHA spectra for calcium, iron, and nickel, emphasizing the significant role of satellite lines in the G ratio at various temperatures, and validates the use of distorted-wave data with resonance effects.

Contribution

It introduces improved models including satellite lines for He-like spectra and confirms the validity of distorted-wave calculations with resonance effects for highly charged ions.

Findings

GD ratio is enhanced at temperatures below He-like maximum abundance.

Satellite lines significantly influence the G ratio, remaining important at high temperatures.

Good agreement between R-matrix and distorted-wave calculations validates the modeling approach.

Abstract

New, more detailed calculations of the emission spectra of the He-like K ALPHA complex of calcium, iron and nickel have been carried out using data from both distorted-wave and R-matrix calculations. The value of the GD ratio (an extended definition of the G ratio that accounts for the effect of resolved and unresolved satellite lines) is significantly enhanced at temperatures below the temperature of He-like maximum abundance. Furthermore it is shown that satellite lines are important contributors to the GD ratio such that GD/G>1 at temperatures well above the temperature of maximum abundance. These new calculations demonstrate, with an improved treatment of the KLn (n>=3) satellite lines, that K ALPHA satellite lines need to be included in models of He like spectra even at relatively high temperatures. The excellent agreement between spectra and line ratios calculated from R-matrix and distorted-wave data also confirms the validity of models based on distorted-wave data for highly charged systems, provided the effect of resonances are taken into account as independent processes.