ExoCross: a general program for generating spectra from molecular line lists

TL;DR

ExoCross is a versatile Fortran program that efficiently generates molecular spectra and thermodynamic properties from various line lists, supporting multiple line profiles, broadening schemes, and formats, including non-LTE spectra simulation.

Contribution

It introduces new methods for fast and accurate Voigt profile calculations and supports the recently proposed super-line approach, enhancing spectral simulation capabilities.

Findings

Efficient parallelization and vectorization for spectral calculations.

Implementation of new methods for Voigt profile computation.

Support for multiple formats and non-LTE spectral simulations.

Abstract

ExoCross is a Fortran code for generating spectra (emission, absorption) and thermodynamic properties (partition function, specific heat etc.) from molecular line lists. Input is taken in several formats, including ExoMol and HITRAN formats. ExoCross is efficiently parallelized showing also a high degree of vectorization. It can work with several line profiles such as Doppler, Lorentzian and Voigt and support several broadening schemes. Voigt profiles are handled by several methods allowing fast and accurate simulations. Two of these methods are new. ExoCross is also capable of working with the recently proposed method of super-lines. It supports calculations of lifetimes, cooling functions, specific heats and other properties. ExoCross can be used to convert between different formats, such as HITRAN, ExoMol and Phoenix. It is capable of simulating non-LTE spectra using a simple two-temperature approach. Different electronic, vibronic or vibrational bands can be simulated separately using an efficient filtering scheme based on the quantum numbers.