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• Code optimization :
• Deactivation by default of the excitation of H, C2H, CC3H2, H13CN, H13CO+, N, CN, S+, and H2_180, and reduction of the default number of SO levels to 30
• Improved determination of the first spatial point to reduce computing time
• Switch of the VOIGT algorithm to the new scheme by Zaghloul & Le Bourlot (2025)
• Bug fixes:
• Correction and update of minor aspects (fix CO full transfer, fix D Doppler width computation, ...)
• Code cleaning:
• Reorganization of some parts of the code
• Clearer naming of subroutines and variables
• ... and many other improvements

• New physical processes and updates of molecular data:
• Add cosmic ray attenuation with Av following Padovani et al. (2018)
• Add a redshift parameter to control the CMB temperature
• Better computation of the emerging spectrum for comparison to observations
• Incident UV radiation fields (ISRF and stellar radiation fields) can now be beamed (previously ISRF was only isotropic).
• Improvement of the treatment of state-to-state chemical reactions
• Add state-to-state reaction : O + H2 -> OH + H (Veselinova et al. 2021)
• Add excitation and line intensity computation of HNC, H13CO+, H13CN, SO, C2H, c-C3H2, and ArH+
• Add collision rates for excited ro-vibrational levels of H2 (Bossion et al. 2018)
• Update of spectroscopic data and collision rates for several atoms and atomic ions : C+, C, S+, S, N+, O+, Si+, N
• Update of spectroscopic data and collision rates for several molecules : H2, H3+, HCO+
• Addition and update of many reactions in the chemical network following the literature and KIDA database (Wakelam et al. 2024). The new chemical network contains 225 species including 13C, 18O and D. There are 8073 reactions.
• Update of photoreaction cross sections for all species that already used them (Hrodmarsson and van Dishoeck 2023)
• Addition of a few continuum band intensities in the output files
• Simplications in the use of the code and its development:
• Control incident UV radiation intensity by directly fixing G0 (Habing) at the PDR surface.
• Better organization of input parameter files and more explicit input parameter names
• Better control on configuration of the incident stellar spectrum
• Add a line list to facilitate line identification in the emerging spectrum
• New format for the collision rate files
• Add explanation in the documentation about how to introduce surface chemistry reactions
• New versions of the analysis tools IDAT and ChemistryAnalyser:
• ChemistryAnalyser version 2 : added new interface to visualize variations in chemical pathways with position across the cloud.
• Better compatibility of the analysis tools IDAT, ChemistryAnalyser and of the Meudon PDR code with recent python versions
• Improvement of robustness and computing time:
• Upgrade and refactoring of several algorithms, in particular several parts of the radiative transfer algorithm.

• Intermediate version used in Berné et al., 2024, Science.

• PDR code is more robust when users impose steep density gradient profiles in .pfl files
• correct an issue with the pumping by the CMB
• correct an issue with H2 cascade coefficients
• better compatibility with Intel ifort compiler
• new IDAT (2.1.4) that is compatible with more python versions and can read HDF5 files produced by different versions of the PDR code
• small update of the Chemistry Analyser

• PDR code and IDAT are compatible with recent versions of numpy and h5py
• correct an issue with OH photodissociation rate
• minor bug corrections

• fixes a bug preventing the use of IDAT in command line

• Allow to use Draine’s grain data and non standard metallicity
• Optimization of HDF5 files writing

• New processes and updates of molecular data
• Line intensities computation of H2_18O
• Implementation of different prescriptions for H2 collisional dissociations
• New default H2 collisional dissociation: Glover & Mac Low 2007)
• Update some UV cross sections ( Heays et al. 2017)
• Update photo-reaction rates ( Heays et al. 2017)
• Update oxygen collision rates ( Lique et al. 2018 )
• Update H2O collision rates ( Daniel et al. 2015 )
• Formation of SH+ using H2 internal energy ( Zanchet et al. 2019)
• 18O fractionation reactions following Loison et al. (2019)
• The isotopologues chemistry has been globally expanded
• Many other updates in the chemical networks and reaction rates following literature and KIDA database
• Update of many molecular data
• Better compatibility of the PDR code with DustEM
• Improvement of robustness and computing time
• Re-design of thermal balance and charge conservation to improve the robustness of the code
• Reduction of the global computation time
• Change in some filenames for windows OS compatibility
• Switch from python 2.7 to python 3.6
• Improvement of output files and analysis tools
• Compatibility of HDF5 output files with IDAT, the new tool to extract and plot computed quantities
• Clarifications of definitions of quantities associated to line profiles
• Switch from python 2.7 to python 3.6 for the analysis tools
• The extractor tool is replaced by IDAT and and is not maintained anymore

• Improvement of the computing time and stability
• Radiative transfer includes absorption in the continuum by several gas species
• A PAH component can be added to the grain distribution
• Can be run synchronously with DustEM 4.0
• New cooling processes have been added for hot gas
• UV pumping and chemical excitation of CO can be considered
• Better integration of the CMB in the radiative pumping
• OH + photon produces electronic excited O
• Update of several hundred chemical rection rates
• New formation rate of CH+ from C+ + excited H2
• Default chemical network includes 13C and 18O chemistry (and minimal D chemistry)
• Chemistry and emission of doubly ionized species added
• Line intensity computations for H3+, OH+, SH+, CH+ added
• Update of radiative and dielectronic recombination rates
• Update of many atomic and molecular data
• Update of Analysis tools (June 2017)

• No continuous absorption by gas species
• Constant dust properties throughout the cloud (allowing analytical integration of some equations)
• No coupling with DustEM
• Update of Analysis tools (June 2017)

PDRLight runs require about 10 minutes on a standard laptop. It can be used for demo or teaching sessions.

• Improvement of the computing time and stability
• Radiative transfer includes absorption in the continuum by several gas species
• A PAH component can be added to the grain distribution
• Can be run synchronously with DustEM 4.0
• New cooling processes have been added for hot gas
• UV pumping and chemical excitation of CO can be considered
• Better integration of the CMB in the radiative pumping
• OH + photon produces electronic excited O
• Update of several hundred chemical rection rates
• New formation rate of CH+ from C+ + excited H2
• Default chemical network includes 13C and 18O chemistry (and minimal D chemistry)
• Chemistry and emission of doubly ionized species added
• Line intensity computations for H3+, OH+, SH+, CH+ added
• Update of radiative and dielectronic recombination rates
• Update of many atomic and molecular data

• No continuous absorption by gas species
• Constant dust properties throughout the cloud (allowing analytical integration of some equations)
• No coupling with DustEM

PDRLight runs require about 10 minutes on a standard laptop. It can be used for demo or teaching sessions.

• Include a version of DustEM
• Improve pumping by external radiation field
• Langmuir-Hinshelwood and Eley Rideal mechanisms
• New excitation collision rates for O
• Computation of O2, OH, and CH+ emission
• Post-treatment to model a pseudo-spherical cloud
• Update of chemistry files

• Improve treatment of grains absorption

• Improve radiative transfer in I.R. and sub-millimeter
• Computation of H2O excitation
• Graphical interfaces
• Virtual Observatory integration

• Possibility to illuminate the slab on two sides
• Photo-ionization & dissociation computed with cross sections

• Third public version of the PDR code

• Second public version of the PDR code

• First public version of the PDR code