iSLAT (the interactive Spectral-Line Analysis Tool) is a python package that provides an interactive interface for the visualization, exploration, and analysis of molecular spectra. Synthetic spectra are made using a simple slab model written by Simon Bruderer and originally described in Banzatti et al. 2012; the code uses molecular data from HITRAN (Gordon et al. 2022, Gordon et al. 2026). iSLAT has been developed for and tested on spectra at infrared wavelengths as observed at different resolving powers (R = 700-90,000) with: JWST-MIRI, Spitzer-IRS, VLT-CRIRES, IRTF-ISHELL. Examples of these spectra are included for users to practice with the tool functionalities across a range of resolving powers. iSLAT has been built as a flexible tool that should work with one-dimensional molecular spectra observed with other instruments too, provided that some requirements are met (see below). The first public version of iSLAT (version 4) is presented and described in Jellison et al. 2024 and is still accessible in the branch version4-retired. This is the new version of iSLAT (version 5), which includes significant improvements and updates as described in the Wiki.
Please see the new wiki page for detailed information on installation, examples, and GUI functions and parameters.
If updating from version 4: clone the new iSLAT in a new folder on your machine, and copy over any save files you may have made with version 4 into the respective folders (e.g. SAVES/ or LINESAVES/ or LINELISTS/).
- McCaskill et al., in prep. (version 5)
- Jellison et al. 2024 (version 4)
- Johnson et al. 2024 (version 4)
- Banzatti et al. 2025 (if you use the "MIRI_general" or other line lists provided in LINELISTS/)
- LMFIT (if you use any of the fitting functions in iSLAT), plus other packages as appropriate.
- Further improvements in speed and computational efficiency
- Particular improvements to the fit saved lines to sample function through batch processing
- Start up speed is now much faster
- Molecule par files are now cached after the first time they are loaded, which greatly improves subsequent loading speed
- Updated to the latest HITRAN release (2024) Gordon et al. 2026
- Added a new setting to the user settings file that automatically removes the year 2020 when loading CSV save files for molecules. This is on by default, but will likely be off by default after the next release
- Created a new wiki page for the tool
- Added several keybinds, which can be seen as tooltips in the GUI or on the new wiki page
- Added new "default_spectra_file_to_load" and "default_line_list_to_load" options to the user settings file. More information on the wiki page
- Created a CHANGELOG.MD file, which features a more detailed list of changes
- Added a large number of example Juypter Notebooks showing some of the ways that you can use iSLAT functions without the GUI
- Made the UserSettings file update when the version number is increased in the default user setting file
Key updates from v5.00.00:
- Further improvements in speed and computational efficiency.
- The slab model now accounts for line opacity overlap and mutual saturation, which is particularly important in the case of water ortho-para lines that overlap (see Figure 5 in Banzatti et al. 2025).
- New functionality to display and save the full spectrum to obtain something similar to Figures 1-4 in Banzatti et al. 2025 (warning: for now this is optimized for JWST MIRI spectra only!)
- "Output full spectrum" in the spectrum parameters menu saves the full spectral range as a single-page PDF file that can be directly included in a paper.
- "Display full spectrum" in the spectrum parameters menu opens a new interactive window to view the full spectrum at the same time as the set of plots in the GUI, to display, for instance, on a second large screen.
- "Toggle full spectrum" in the main GUI toggles an interactive view of the full spectrum in the main window, by replacing the default zoomed-in plots.
- The thermal broadening is calculated and displayed for reference for each molecule at the temperature set by the user.
- The molar mass of each molecule is now saved in their respective Hitran Files.
Main updates from version 4:
- Substantial speed improvement from global refactoring of the code and data architecture
- Improved management of molecular models (now including the option to have individual RV shift and broadening)
- New function to measure line fluxes on a sample rather than on single spectrum ("Fit Saved Lines to sample")
- Several improvements to GUI organization and interactivity