Comments on the Voigt function implementation in the Astropy and SpectraPlot.com packages

TL;DR

This paper evaluates the accuracy of existing Voigt function implementations in Astropy and SpectraPlot, identifies significant errors in some algorithms, and recommends more reliable rational approximation methods for spectroscopy applications.

Contribution

It provides a critical assessment of current Voigt function algorithms and proposes improved rational approximation techniques for better accuracy in spectroscopy.

Findings

Existing algorithms have significant errors for small arguments.

Some implementations are efficient but lack accuracy.

Recommended rational approximation methods improve reliability.

Abstract

The Voigt profile is important for spectroscopy, astrophysics, and many other fields of physics, but is notoriously difficult to compute. McLean et al. [J. Electron Spectrosc. & Relat. Phenom., 1994] have proposed an approximation using a sum of Lorentzians. Our assessment indicates that this algorithm has significant errors for small arguments. After a brief survey of the requirements for spectroscopy we give a short list of both efficient and accurate codes and recommend implementations based on rational approximations.