A rational approximation for efficient computation of the Voigt function in quantitative spectroscopy

Abstract

We present a rational approximation for rapid and accurate computation of the Voigt function, obtained by residue calculus. The computational test reveals that with only $16$ summation terms this approximation provides average accuracy ${10^{- 14}}$ over a wide domain of practical interest $0 < x < 40,000$ and ${10^{- 4}} < y < {10^2}$ for applications using the HITRAN molecular spectroscopic database. The proposed rational approximation takes less than half the computation time of that required by Weideman's rational approximation. Algorithmic stability is achieved due to absence of the poles at $y \geqslant 0$ and $ - \infty < x < \infty $.