Accurate determination of the free-free Gaunt factor; I - non-relativistic Gaunt factors

TL;DR

This paper provides a comprehensive and highly accurate set of non-relativistic free-free Gaunt factors over an extensive parameter space, essential for precise spectral modeling of ionized plasmas.

Contribution

It presents the first extensive tables of non-averaged, thermally averaged, and frequency integrated Gaunt factors covering wider parameter ranges than previously available.

Findings

Produced detailed tables of non-averaged Gaunt factors.

Generated thermally averaged Gaunt factors over a broad parameter space.

Provided frequency integrated Gaunt factors for extensive parameters.

Abstract

Modern spectral synthesis codes need the thermally averaged free-free Gaunt factor defined over a very wide range of parameter space in order to produce an accurate prediction for the spectrum emitted by an ionized plasma. Until now no set of data exists that would meet this need in a fully satisfactory way. We have therefore undertaken to produce a table of very accurate non-relativistic Gaunt factors over a much wider range of parameters than has ever been produced before. We first produced a table of non-averaged Gaunt factors, covering the parameter space log10(epsilon_i) = -20 to +10 and log10(w) = -30 to +25. We then continued to produce a table of thermally averaged Gaunt factors covering the parameter space log10(gamma^2) = -6 to +10 and log10(u) = -16 to +13. Finally we produced a table of the frequency integrated Gaunt factor covering the parameter space log10(gamma^2) = -6 to +10. All the data presented in this paper are available online.