Written as a general purpose radiative solver, the code is built around the [HITRAN-2020], [HITEMP-2010] and [CDSD-4000] databases for molecules in their electronic ground state. Energy levels are read from tabulated databases or calculated from Dunham developments. Boltzmann, Treanor, and state specific vibrational distributions can be generated. Thus far, CO2, CO are featured for non-equilibrium calculations (MOLECULES_LIST_NONEQUILIBRIUM), and all species present in the HITRAN database are featured for equilibrium calculations (MOLECULES_LIST_EQUILIBRIUM).

To fit experimental spectra, RADIS includes a LineSurvey tool, an interface with a look-up SpecDatabase to improve fitting convergence times, and a multi-slab module with a radiative transfer equation solver to reproduce line-of-sight experiments. Validation cases against existing spectral codes and experimental results from various plasma sources are included [RADIS-2018].


RADIS is both an infrared line-by-line code and a post-processing library. It includes:

RADIS does not include, so far:

  • Line-mixing effects and speed-dependant lineshapes. [HAPI] is a Python alternative that does it.

  • Collisional-induced absorption (CIA) or emission.

  • Electronic states other than electronic ground states

  • Hamiltonian calculations (a private module for CO2 is available on request)

  • Raman spectra (contribute in #43)

RADIS also features:

  • High Performances: spectra are calculated up to several orders of magnitude faster than equivalent line-by-line codes.

  • In-the-browser calculations (no install needed) : see 🌱 RADIS Online.

  • Automatic download of the latest HITRAN and HITEMP databases with calc_spectrum()

  • Automatic testing and continuous integration tools for a reliable Open-source Development.

Remarks and request for features can be done on GitHub , on the Q&A forum or on the Gitter community chat:

Gitter Slack

Use Cases

Use RADIS to:

  • Quickly compare different line databases: Various line database formats are supported by RADIS, and can be easily switched to be compared. See the list of supported line databases formats: KNOWN_DBFORMAT and refer to the Configuration file on how to use them.

    See the comparison of two CO2 spectra calculated with [HITEMP-2010] and [CDSD-4000] below:

  • Use the RADIS post-processing methods with the calculation results of another spectral code. For instance, pySpecair, the Python interface to SPECAIR, uses the RADIS Spectrum object for post-processing (see How to generate a Spectrum?)

Refer to the Examples section for more examples, or to the RADIS Interactive Examples project.

See the Architecture section for an overview of the RADIS calculation steps.

Line Databases

List of supported line databases formats: KNOWN_DBFORMAT :

For download and configuration of line databases, see the Line Databases section


RADIS includes parsers and interfaces to read and return data in different formats:

Thermodynamic codes


RADIS can compute gas mixture compositions under chemical equilibrium using CANTERA (in particular the [CANTERA] equilibrate() function). Refer to get_eq_mole_fraction() for more information.

New features

RADIS is open-source, so everyone can contribute to the code development. Read the Developer Guide to get started.

You can also suggest or vote for new features below: