Database Downloading

PyExoCross provides a built-in Python API for downloading molecular and atomic data from external databases, including ExoMol, ExoAtom, ExoMolHR, and HITRAN.

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Python API Usage

All database downloads are handled through the main function pyexocross.download().

import pyexocross as px

px.download(database, file_path=None, **kwargs)

Common Parameters

Parameter	Type	Required	Description
database	str	Yes	Database name: 'ExoMol', 'ExoAtom', 'ExoMolHR', or 'HITRAN'
file_path	str	Yes	Folder where the downloaded files will be saved, can also use save_path
species_info	dict	Yes	Molecule/isotopologue or atom configuration dict
download	bool	yes	If True (default), download the files. If False, only generate the URL list file.
wn_range	list	Optional	Filter transitions by wavenumber range (cm⁻¹).
T	int	Optional	Temperature in Kelvin.
threshold	float	Optional	Minimum line intensity threshold in cm/molecule.
dataset	str	Optional	The dataset to use. Can be either 'NIST' or 'Kurucz'.

Species Configuration Details (species_info)

The dictionary structure for species_info allows you to customize the files to be downloaded. You can specify parameters such as:

• wn_range (list of two floats: [wn_min, wn_max]): Filter transition files by wavenumber range (in cm⁻¹).

  • ExoMol: Used to download only the segmented transition files (.trans.bz2) that fall completely within the requested range.

  • HITRAN / ExoMolHR: Used to query and download the line transitions matching this specific range.

• T or temperature (int): Temperature (in Kelvin) for fetching temperature-dependent high-resolution datasets.

  • ExoMolHR: Required for online query-based CSV download.

• threshold or Smin (float): The minimum line intensity threshold (in cm/molecule).

  • ExoMolHR: Required for online query-based CSV download to filter weak lines.

• dataset (str): The dataset to use. Required for ExoAtom downloads.

  • ExoAtom: Can be either 'NIST' (critically evaluated and recommended for accuracy) or 'Kurucz' (recommended for completeness).

Database	Required Parameters	Optional Parameters
'ExoMol'	database, file_path, species_info, download	wn_range
'ExoMolHR'	database, file_path, species_info, download	T, threshold, wn_range
'ExoAtom'	database, file_path, species_info, download	dataset
'HITRAN'	database, file_path, species_info, download	wn_range

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1. ExoMol Database (database='ExoMol')

Downloads line lists, states, transition files, and partition functions from the ExoMol database.

Example

px.download(
    database='ExoMol',
    file_path='/path/to/ExoMol/',
    species_info={
        'MgH': {
            '24Mg-1H': {'wn_range': None},
            '25Mg-1H': {'wn_range': None},
        },
        'H2O': {
            '1H2-16O': {'wn_range': [41000, 41200]},
        },
    },
    download=True,
)

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2. ExoMolHR Database (database='ExoMolHR')

Downloads high-resolution line lists and partition functions. It queries the server for a dynamically calculated CSV file based on your specified temperature (T), wavenumber range (wn_range), and intensity threshold (threshold).

Example

px.download(
    database='ExoMolHR',
    file_path='/path/to/ExoMolHR/',
    species_info={
        'MgH': {
            '24Mg-1H': {'T': 1000, 'wn_range': [0, 500], 'threshold': 1e-30},
            '25Mg-1H': None,
        },
        'AlH': {
            '27Al-1H': {'T': 500, 'wn_range': [0, 500], 'threshold': 1e-30}
        },
    },
    download=True,
)

---

3. ExoAtom Database (database='ExoAtom')

Downloads atomic transitions and energy levels from the NIST or Kurucz databases using the ExoAtom configuration.

Example

px.download(
    database='ExoAtom',
    file_path='/path/to/ExoAtom/',
    species_info={
        'He': {'dataset': 'NIST'},
        'He_p': {'3He_p': {'dataset': 'NIST'}},
        'Ar_p': {'dataset': 'Kurucz'},
    },
    download=True,
)

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4. HITRAN Database (database='HITRAN')

Downloads line-by-line spectroscopic data and partition functions directly from the HITRAN database via the HITRANonline API.

Example

px.download(
    database='HITRAN',
    file_path='/path/to/HITRAN/',
    species_info={
        'NO': {
            '14N-16O': {'wn_range': [0, 100]},
            '15N-16O': {'wn_range': [100, 150]},
        },
        'H2O': {
            '1H2-16O': {'wn_range': [100, 110]},
        },
    },
    download=True,
)

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Generating URLs Only

If you only want to generate the list of URLs to be downloaded later, set download=False:

px.download(
    database='ExoMol',
    file_path='/path/to/ExoMol/',
    species_info={'MgH': {'24Mg-1H': None}},
    download=False,
)

This will save the URLs to /path/to/ExoMol/url/exomol__urls.txt and print them to the console.