Functions Reference

All functions are accessible from the top-level pyexocross namespace:

import pyexocross as px

Every function accepts either:

• An .inp file path via inp_filepath, or

• Keyword arguments (**kwargs), or

• Both (keyword arguments override .inp file values).

Common CPU/GPU Compute Kwargs

PyExoCross uses CPU by default. You can explicitly select compute mode with:

Kwarg	Type	Default	Description
device or run_mode	str	'CPU'	'CPU' or 'GPU'
gpu_backend	str	'AUTO'	GPU backend policy: 'AUTO', 'CUDA', 'PyTorch-CUDA', 'CuPy-CUDA', or 'MPS'
gpu_batch_lines	int	8192	GPU line-batch size for memory control
gpu_batch_grid	int	256	GPU grid-batch size for memory control

GPU acceleration is available for:

• px.cooling_functions -> Recommend to use CPU mode

• px.stick_spectra -> Recommend to use CPU mode

• px.cross_sections

• px.stick_spectra_cross_section

CPU formulas are used for:

• px.conversion

• px.partition_functions

• px.specific_heats

• px.lifetimes

• px.oscillator_strengths

If device='GPU' but no compatible backend is available, PyExoCross falls back to CPU formulas.

# Default CPU mode
px.cross_sections(..., device='CPU')

# GPU mode (auto backend)
px.cross_sections(
    ...,
    device='GPU',
    gpu_backend='AUTO',
    gpu_batch_lines=8192,
    gpu_batch_grid=256,
)

# CUDA policy: PyTorch-CUDA -> CuPy-CUDA -> MPS -> CPU fallback
px.cross_sections(..., device='GPU', gpu_backend='CUDA')

# Force PyTorch CUDA only
px.cross_sections(..., device='GPU', gpu_backend='PyTorch-CUDA')

# Force CuPy CUDA only
px.cross_sections(..., device='GPU', gpu_backend='CuPy-CUDA')

# Force PyTorch MPS only
px.cross_sections(..., device='GPU', gpu_backend='MPS')

---

px.load

data = px.load(..., cache='auto', cache_dir=None, max_memory=512,
               all_transitions=False)

Loads and preprocesses reusable ExoMol, ExoAtom, ExoMolHR, HITRAN, or HITEMP data. auto keeps small inputs in memory and converts large inputs to Parquet; parquet forces persistent Parquet caching; none uses the original input format. Use the result with data= in px.conversion, px.partition_functions, px.specific_heats, px.lifetimes, px.cooling_functions, px.oscillator_strengths, px.stick_spectra, px.cross_sections, or px.stick_spectra_cross_section.

Parameters

Parameter	Type	Required	Description
inp_filepath	str or None	No	Optional .inp file; keyword arguments override file values
database	str	Yes*	ExoMol, ExoAtom, ExoMolHR, HITRAN, or HITEMP
molecule	str	Conditional	Required for molecular databases
atom	str	Conditional	Required for ExoAtom
isotopologue	str	Conditional	Required except for ExoAtom
dataset	str	Yes*	Line-list dataset name
species_id	int or None	No	Species identifier; needed by conversions that write HITRAN IDs
read_path	str	Yes*	Database root containing the input line list
save_path	str	No	Output root retained for later calculations; default ./output/
logs_path	str or None	No	Log path retained for later calculations; None disables file logging
min_range	float	No	Initial minimum wavenumber/wavelength; default 0
max_range	float	No	Initial maximum wavenumber/wavelength; default 30000
wn_wl	str	No	Range coordinate, WN or WL; default WN
wn_wl_unit	str	No	cm-1, um, or nm; default cm-1
unc_filter	float or None	No	Maximum uncertainty retained during preprocessing; default None
cache	str	No	auto, parquet, or none; default auto
cache_dir	str or None	No	Persistent cache directory; default is source-adjacent .pyexocross_cache/
max_memory	int	No	Auto-mode memory threshold in MB; default 512
refresh	bool	No	Rebuild matching persistent caches; default False
all_transitions	bool	No	Eagerly load all transition files; default False
device or run_mode	str	No	CPU or GPU; default CPU
gpu_backend	str	No	GPU backend policy; default AUTO
gpu_batch_lines	int	No	GPU line-batch limit; default 8192
gpu_batch_grid	int	No	GPU grid-batch limit; default 256
chunk_size	int	No	Rows read per transition chunk; default 100000

* Not required when supplied by inp_filepath.

Later calculations may provide their own min_range and max_range as long as that interval is covered by the data loaded here. A wider interval requires another px.load. The cutoff value does not expand the range required from px.load. Range errors report the exact recommended min_range and max_range for the next load.

A later unc_filter may keep the loaded value or use a smaller, stricter value; PyExoCross then filters the loaded data further. A larger value, or changing a numeric filter to None, requires another px.load and the error reports the required filter value.

For ExoMol and ExoAtom, a later qns_filter may add constraints or narrow the values retained by px.load. Empty value lists are wildcards and do not filter the loaded states. Removing an active constraint or adding values excluded by px.load requires loading the data again. HITRAN, HITEMP, and ExoMolHR retain the complete line table and apply QN filters during each calculation.

For ExoMol/ExoAtom, calling px.lifetimes, px.cooling_functions, or px.oscillator_strengths automatically expands range-loaded data to all transitions and updates the same object for reuse.
Set all_transitions=True only when this work should be done eagerly.
Partition functions and specific heats reuse states and database metadata from LoadedData but do not read or expand transitions.

Example

data = px.load(
    database='ExoMol',
    molecule='MgH',
    isotopologue='24Mg-1H',
    dataset='XAB',
    read_path='/path/to/ExoMol/',
    save_path='/path/to/output/',
    logs_path='/path/to/output/log/MgH.log',
    min_range=0,
    max_range=10000,
    cache='auto',  
    max_memory=512,
    device='CPU',
)

# A narrower calculation range reuses the loaded data.
px.cross_section(
    data=data,
    min_range=1000,
    max_range=2000,
    temperatures=[296, 1000],
    pressures=[1.0],
)

# This first whole-list calculation automatically loads all transitions.
px.lifetimes(data=data)

# These calls reuse the automatically expanded object.
px.cooling_functions(data=data)
px.oscillator_strengths(data=data)

The original direct API remains available and still performs loading, preprocessing, calculation, and saving in one call.

The direct API can also use the same cache without calling px.load:

px.conversion(..., cache='auto')
px.lifetimes(..., cache='auto')
px.cooling_functions(..., cache='auto')
px.oscillator_strengths(..., cache='auto')
px.stick_spectra(..., cache='auto')
px.cross_section(..., cache='auto')
px.stick_spectra_cross_section(..., cache='auto')

With cache_dir=None, PyExoCross stores persistent files in <read_path>/<data_info>/.pyexocross_cache/. Initial conversion takes extra time; subsequent runs reuse the cache if the source path, size, and modification time are unchanged. Set refresh=True to rebuild it. max_memory is specified in MB. The default max_memory=512 is converted internally to 512 * 1024**2 bytes and only limits transition data retained by cache='auto'; it is not a limit on total process memory.

The same Parquet files work in CPU and GPU modes. Current Parquet reading, decompression, and preprocessing run on the CPU through PyArrow. GPU mode accelerates supported calculation kernels after the required arrays are loaded.

For range-based spectra and cross sections, Parquet mode stores filtered files under <cache_dir>/ranges/ using names with specified ranges.
A finite cutoff expands the cached interval only inside the transition files selected by the original calculation range; it does not add adjacent source files. Cache validity and source metadata are stored in <cache_dir>/manifest.json. When several valid caches cover a request, PyExoCross selects the narrowest interval and prints the number, intervals, and total size of range cache files.
The complete states table is also stored in a parquet file.
Its source path, size, and modification time are tracked in the same manifest instead of being embedded in the filename.

HITRAN/HITEMP fixed-width files and ExoMolHR CSV files are normalized once and stored as database-prefixed, range-named *__00000-30000.linelist.parquet files. Their existing v column is used for row-group range filtering, while uncertainty and intensity filters remain calculation parameters. With cache_dir=None, these caches are stored in .pyexocross_cache beside the source .par or .csv file.

---

px.run

px.run(inp_filepath, force_reload=False)

Run all enabled functions from an .inp configuration file. This is the programmatic equivalent of running python3 run.py -p <inp_filepath> from the command line.

Parameters

Parameter	Type	Required	Description
inp_filepath	str	Yes	Path to the .inp configuration file
force_reload	bool	No	Force re-parse of .inp even when cached in current Python process (default: False)

Note

If you edit the same .inp file repeatedly in a long-lived session (e.g. Jupyter), use force_reload=True to avoid reusing stale cached parameters.

Example

px.run('/path/to/MgH_ExoMol.inp')

# Re-read updated .inp content in the same session
px.run('/path/to/MgH_ExoMol.inp', force_reload=True)

---

px.download

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

Download database files from external servers. Supported databases are ExoMol, ExoMolHR, ExoAtom, and HITRAN.

Parameters

Parameter	Type	Required	Description
database	str	Yes	Name of the database to download: 'ExoMol', 'ExoMolHR', 'ExoAtom', or 'HITRAN'.
file_path	str	Yes	Path to save the downloaded files (e.g. /path/to/database/), can also use save_path.
species_info	dict	Yes	Molecule/isotopologue or atom configuration dictionary.
download	bool	Yes	If True (default), download the files. If False, only generate the URL 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 Options (species_info)

Inside species_info, you can configure the following optional settings:

• wn_range (list/tuple of [wn_min, wn_max]): Filter transitions by wavenumber range (cm⁻¹). Supported by ExoMol (downloads only segmented transition files fully within range), ExoMolHR, and HITRAN.

• T or temperature (int): Temperature in Kelvin. Required for ExoMolHR online query downloads.

• threshold or Smin (float): Minimum line intensity threshold in cm/molecule. Required for ExoMolHR online query downloads to filter out weaker lines.

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

Examples

ExoMol Download

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,
)

ExoMolHR Download

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

ExoAtom Download

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,
)

HITRAN Download

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,
)

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.

---

px.conversion

px.conversion(inp_filepath=None, **kwargs)

Convert between ExoMol/ExoMolHR/ExoAtom and HITRAN line-list formats.

Parameters

Parameter	Type	Default	Description
inp_filepath	str	None	Path to .inp file
database	str	'ExoMol'	'ExoMol', 'ExoMolHR', 'ExoAtom', 'HITRAN', or 'HITEMP'
molecule	str	None	Molecule name (e.g. 'MgH', 'NO')
atom	str	None	Atom name for ExoAtom (e.g. 'Ar', 'Li')
isotopologue	str	None	Isotopologue (e.g. '24Mg-1H', '14N-16O')
dataset	str	None	Dataset name (e.g. 'XAB', 'NIST')
species_id	int	0	Species identifier (e.g. 501, 81)
read_path	str	'./'	Path to input database
save_path	str	'./output/'	Path for output files
logs_path	str	None	Log file path
conversion_format	str	None	'ExoMo' = HITRAN/HITEMP -> ExoMol/ExoAtom, 'HITRAN' = ExoMol/ExoMolHR/ExoAtom -> HITRAN/HITEMP
conversion_min_freq	float	0	Minimum frequency in cm⁻¹
conversion_max_freq	float	1e10	Maximum frequency in cm⁻¹
conversion_unc	float or None	None	Uncertainty filter (cm⁻¹); None to disable
conversion_threshold	float or None	None	Intensity threshold (cm/molecule); None to disable
global_qn_label_list	list[str]	[]	Global quantum number labels for HITRAN output
global_qn_format_list	list[str]	[]	Global QN format specifiers (total 15 chars in HITRAN2004)
local_qn_label_list	list[str]	[]	Local quantum number labels for HITRAN output
local_qn_format_list	list[str]	[]	Local QN format specifiers (total 15 chars in HITRAN2004)
qnslabel_list	list[str]	[]	Optional quantum number label override; ExoMol/ExoMolHR/ExoAtom labels are derived from definition metadata by default
qnsformat_list	list[str]	[]	Optional quantum number format override; ExoMol/ExoMolHR/ExoAtom formats are derived from definition metadata by default
ncputrans	int	4	CPU cores for processing transitions
ncpufiles	int	1	Files processed simultaneously
chunk_size	int	100000	Chunk size for transitions
cache	str	'auto'	'auto', 'parquet', or 'none'
cache_dir	str or None	None	Persistent cache directory
max_memory	int	512	Auto-mode memory threshold in MB

Legacy Aliases

px.convert_exomol_to_hitran(...)     # Sets conversion_format='HITRAN'
px.convert_exomolhr_to_hitran(...)   # Sets conversion_format='HITRAN'
px.convert_exoatom_to_hitran(...)    # Sets conversion_format='HITRAN'
px.convert_hitran_to_exomol(...)     # Sets conversion_format='ExoMol'

Example

px.conversion(
    database='ExoMol',
    molecule='MgH',
    isotopologue='24Mg-1H',
    dataset='XAB',
    species_id=501,
    read_path='/path/to/ExoMol/',
    save_path='/path/to/output/',
    conversion_format='HITRAN',
    global_qn_label_list=['ElecState', 'v', 'Omega'],
    global_qn_format_list=['%9s', '%2d', '%4s'],
    local_qn_label_list=['J', 'e/f'],
    local_qn_format_list=['%5.1f', '%2s'],
)

---

px.partition_functions

px.partition_functions(inp_filepath=None, **kwargs)

Calculate partition functions \(Q(T) = \sum_n g_n^{\text{tot}} \exp(-c_2 \tilde{E}_n / T)\).

Parameters

Parameter	Type	Default	Description
inp_filepath	str	None	Path to .inp file
database	str	'ExoMol'	Database name
molecule	str	None	Molecule name
atom	str	None	Atom name (ExoAtom)
isotopologue	str	None	Isotopologue
dataset	str	None	Dataset name
species_id	int	0	Species identifier
read_path	str	'./'	Input database path
save_path	str	'./output/'	Output path
logs_path	str	None	Log file path
ntemp	int	1	Temperature step in K
tmax	int	5000	Maximum temperature in K
ncputrans	int	4	CPU cores for transitions
ncpufiles	int	1	Files processed simultaneously
chunk_size	int	100000	Chunk size

Legacy Alias: px.partition_function

Example

px.partition_functions(
    database='ExoMol',
    molecule='MgH',
    isotopologue='24Mg-1H',
    dataset='XAB',
    species_id=501,
    read_path='/path/to/ExoMol/',
    save_path='/path/to/output/',
    ntemp=1,
    tmax=5000,
)

---

px.specific_heats

px.specific_heats(inp_filepath=None, **kwargs)

Calculate specific heat capacities \(C_p(T)\) using partition function derivatives.

Parameters: Same as px.partition_functions.

Legacy Alias: px.specific_heat

Example

px.specific_heats(
    database='ExoMol',
    molecule='MgH',
    isotopologue='24Mg-1H',
    dataset='XAB',
    species_id=501,
    read_path='/path/to/ExoMol/',
    save_path='/path/to/output/',
    ntemp=1,
    tmax=5000,
)

---

px.cooling_functions

px.cooling_functions(inp_filepath=None, **kwargs)

Calculate cooling functions:

\[W(T) = \frac{1}{4\pi Q(T)} \sum_{f,i} A_{fi}\, h c \tilde{\nu}_{fi}\, g'\, \exp\!\left(-\frac{c_2 \tilde{E}'}{T}\right)\]

Parameters

Same as px.partition_functions, plus optional compute backend kwargs:

Parameter	Type	Default	Description
device or run_mode	str	'CPU'	'CPU' or 'GPU'
gpu_backend	str	'AUTO'	'AUTO', 'CUDA', 'PyTorch-CUDA', 'CuPy-CUDA', or 'MPS'
gpu_batch_lines	int	8192	GPU line-batch size (memory control)
gpu_batch_grid	int	256	GPU grid-batch size (memory control)

Legacy Alias: px.cooling_function

Example

px.cooling_functions(
    database='ExoMol',
    molecule='MgH',
    isotopologue='24Mg-1H',
    dataset='XAB',
    species_id=501,
    read_path='/path/to/ExoMol/',
    save_path='/path/to/output/',
    ntemp=1,
    tmax=5000,
    device='CPU',
)

---

px.lifetimes

px.lifetimes(inp_filepath=None, **kwargs)

Calculate radiative lifetimes: $\(\tau_i = 1 / \sum_f A_{fi}\)$

Parameters

Parameter	Type	Default	Description
inp_filepath	str	None	Path to .inp file
database	str	'ExoMol'	Database name
molecule	str	None	Molecule name
atom	str	None	Atom name (ExoAtom)
isotopologue	str	None	Isotopologue
dataset	str	None	Dataset name
species_id	int	0	Species identifier
read_path	str	'./'	Input database path
save_path	str	'./output/'	Output path
logs_path	str	None	Log file path
compress	bool	False	True to save as .bz2; False for uncompressed
ncputrans	int	4	CPU cores for transitions
ncpufiles	int	1	Files processed simultaneously
chunk_size	int	100000	Chunk size

Legacy Alias: px.lifetime

Example

px.lifetimes(
    database='ExoMol',
    molecule='MgH',
    isotopologue='24Mg-1H',
    dataset='XAB',
    species_id=501,
    read_path='/path/to/ExoMol/',
    save_path='/path/to/output/',
    compress=False,
)

---

px.oscillator_strengths

px.oscillator_strengths(inp_filepath=None, **kwargs)

Calculate oscillator strengths: weighted \(gf = g_{\text{tot}}' A_{fi} / (c \tilde{\nu}_{fi})^2\) or unweighted \(f\)-values.

Parameters

Parameter	Type	Default	Description
inp_filepath	str	None	Path to .inp file
database	str	'ExoMol'	Database name
molecule	str	None	Molecule name
atom	str	None	Atom name (ExoAtom)
isotopologue	str	None	Isotopologue
dataset	str	None	Dataset name
species_id	int	0	Species identifier
read_path	str	'./'	Input database path
save_path	str	'./output/'	Output path
logs_path	str	None	Log file path
gf_or_f	str	'f'	'gf' for weighted, 'f' for unweighted
ncputrans	int	4	CPU cores for transitions
ncpufiles	int	1	Files processed simultaneously
chunk_size	int	100000	Chunk size
plot	bool	False	Whether to generate a plot
plot_method	str	'log'	'log' or 'linear'
plot_wn_wl	str	'WN'	'WN' (wavenumber) or 'WL' (wavelength)
plot_unit	str	'cm-1'	'cm-1', 'um', or 'nm'
limit_yaxis	float	1e-30	Lower limit for y-axis

Legacy Alias: px.oscillator_strength

Example

px.oscillator_strengths(
    database='ExoMol',
    molecule='MgH',
    isotopologue='24Mg-1H',
    dataset='XAB',
    species_id=501,
    read_path='/path/to/ExoMol/',
    save_path='/path/to/output/',
    gf_or_f='f',
    plot=True,
    plot_method='log',
    plot_wn_wl='WN',
    plot_unit='cm-1',
    limit_yaxis=1e-30,
)

---

px.stick_spectra

px.stick_spectra(inp_filepath=None, **kwargs)

Calculate LTE or Non-LTE stick spectra (absorption or emission).

Parameters

Parameter	Type	Default	Description
inp_filepath	str	None	Path to .inp file
Species
database	str	'ExoMol'	'ExoMol', 'ExoAtom', 'HITRAN', or 'HITEMP'
molecule	str	None	Molecule name
atom	str	None	Atom name (ExoAtom)
isotopologue	str	None	Isotopologue
dataset	str	None	Dataset name
species_id	int	0	Species identifier
Paths
read_path	str	'./'	Input database path
save_path	str	'./output/'	Output path
logs_path	str	None	Log file path
Physical conditions
temperatures	list[float]	[1000]	Temperature(s) in K
wn_wl	str	'WN'	'WN' (wavenumber) or 'WL' (wavelength)
wn_wl_unit	str	'cm-1'	'cm-1', 'um', or 'nm'
min_range	float	0	Minimum range value (in wn_wl_unit)
max_range	float	30000	Maximum range value (in wn_wl_unit)
abs_emi	str	'Ab'	'Ab' for absorption, 'Em' for emission
abundance	float	1.0	Optional isotopic abundance multiplier
Non-LTE
nlte_method	str	'L'	'L'=LTE, 'T'=Treanor, 'D'=Density, 'P'=Population
tvib_list	list[float]	[]	Vibrational temperatures for method 'T'
trot_list	list[float]	[]	Rotational temperatures for method 'T' or 'D'
vib_label	list[str]	[]	Vibrational QN labels for method 'T'
rot_label	list[str]	[]	Rotational QN labels for method 'T'
nlte_path	str	None	Path to NLTE data file (methods 'D' and 'P')
Filters
threshold	float or None	None	Intensity threshold (cm/molecule); None to disable
unc_filter	float or None	None	Uncertainty filter (cm⁻¹); None to disable
qns_filter	dict or None	None	Quantum number filter (see below)
Quantum numbers
qnslabel_list	list[str]	[]	Optional QN label override; ExoMol/ExoAtom labels are derived from definition metadata by default
qnsformat_list	list[str]	[]	Optional QN format override; ExoMol/ExoAtom formats are derived from definition metadata by default
Computing
ncputrans	int	4	CPU cores for transitions
ncpufiles	int	1	Files processed simultaneously
chunk_size	int	100000	Chunk size
device or run_mode	str	'CPU'	'CPU' or 'GPU'
gpu_backend	str	'AUTO'	'AUTO', 'CUDA', 'PyTorch-CUDA', 'CuPy-CUDA', or 'MPS'
gpu_batch_lines	int	8192	GPU line-batch size (memory control)
gpu_batch_grid	int	256	GPU grid-batch size (memory control)
Plotting
plot	bool	False	Whether to generate a plot
plot_method	str	'log'	'log' or 'linear'
plot_wn_wl	str	'WN'	X-axis: 'WN' or 'WL'
plot_unit	str	'cm-1'	'cm-1', 'um', or 'nm'
limit_yaxis	float	1e-30	Lower limit for y-axis (cm/molecule)

Note

wn_wl and wn_wl_unit define the calculation range, saved file name, and the first column of the saved .stick file.
Use wn_wl='WN', wn_wl_unit='cm-1' to save wavenumber, or wn_wl='WL', wn_wl_unit='nm'/'um' to save wavelength.
plot_wn_wl and plot_unit only control the plot x-axis.

Quantum Number Filter (qns_filter)

The qns_filter parameter accepts a dictionary where keys are quantum number labels and values are lists of accepted value patterns. Use an empty list [] to accept all values for that label.

qns_filter={
    '+/-': [],                    # accept all parities
    'v': ['0,', '1,', '2,'],      # only v' = 0, 1, 2
    'ElecState': [],              # accept all electronic states
}

Example

px.stick_spectra(
    database='ExoMol',
    molecule='MgH',
    isotopologue='24Mg-1H',
    dataset='XAB',
    species_id=501,
    read_path='/path/to/ExoMol/',
    save_path='/path/to/output/',
    temperatures=[1000, 2000],
    wn_wl='WN',
    wn_wl_unit='cm-1',
    min_range=0,
    max_range=30000,
    abs_emi='Ab',
    abundance=1.0,
    device='CPU',
)

---

px.cross_sections

px.cross_sections(inp_filepath=None, **kwargs)

Calculate LTE or Non-LTE cross sections with a choice of line profiles.

Parameters

All parameters from px.stick_spectra, plus:

Parameter	Type	Default	Description
Grid
pressures	list[float]	[1.0]	Pressure(s) in bar
bin_size	float	0.1	Bin size (in wn_wl_unit); mutually exclusive with n_point
n_point	int	None	Number of grid points; mutually exclusive with bin_size
Line profile
profile	str	'Gaussian'	Line profile (see table below)
cutoff	float or None	None	Wing cutoff in cm⁻¹; None to disable
predissociation	bool	False	Use predissociation lifetimes for Voigt width
Broadening
broadeners	list[str]	['Default']	Broadening species
ratios	list[float]	[1.0]	Broadener mixing ratios (must sum to 1.0)
alpha_hwhm	float or None	None	Constant Doppler HWHM; None to calculate
gamma_hwhm	float or None	None	Constant Lorentzian HWHM; None to calculate
Plotting
plot	bool	False	Whether to generate a plot
plot_method	str	'log'	'log' or 'linear'
plot_wn_wl	str	'WN'	X-axis: 'WN' or 'WL'
plot_unit	str	'cm-1'	'cm-1', 'um', or 'nm'
limit_yaxis	float	1e-30	Lower limit for y-axis (cm\(^2\)/molecule)

Note

The cross-section grid is built in the selected wn_wl_unit.
For example, with wn_wl='WL', wn_wl_unit='nm', min_range, max_range, bin_size, the saved file name, and the first column of the saved .xsec file all use nm.
The plot axis can be changed independently with plot_wn_wl and plot_unit. Line-profile widths and cutoff remain in cm⁻¹.

Available Line Profiles

Profile Name	Description
'Doppler'	Pure Doppler profile
'Gaussian'	Gaussian profile
'Lorentzian'	Lorentzian profile
'SciPyVoigt'	Voigt via SciPy wofz (recommended)
'SciPyWofzVoigt'	Voigt via SciPy wofz (alternative)
'HumlicekVoigt'	Humlicek algorithm for Voigt
'PseudoVoigt'	Generic pseudo-Voigt
'PseudoThompsonVoigt'	Thompson pseudo-Voigt approximation
'PseudoKielkopfVoigt'	Kielkopf pseudo-Voigt approximation
'PseudoOliveroVoigt'	Olivero pseudo-Voigt approximation
'PseudoLiuLinVoigt'	Liu-Lin pseudo-Voigt approximation
'PseudoRoccoVoigt'	Rocco pseudo-Voigt approximation
'BinnedDoppler'	Binned Doppler profile
'BinnedGaussian'	Binned Gaussian profile
'BinnedLorentzian'	Binned Lorentzian profile
'BinnedVoigt'	Binned Voigt profile

Available Broadeners

Broadener	Description
'Default'	Default broadening parameters
'Air'	Air broadening (N\(_2\) + O\(_2\))
'Self'	Self broadening
'H2'	Hydrogen broadening
'He'	Helium broadening
'CO2'	CO\(_2\) broadening
'H2O'	Water broadening
<molecule> or <atom>	or broadening

Support all broadening files format from ExoMol database.

For HITRAN and HITEMP, Default uses air broadening (gamma_air), consistent with the standard HAPI convention (GammaL='gamma_air').

For standard HITRAN air-broadened calculations, use:

broadeners=['Air'],
ratios=[1.0],

To mix air and self broadening, use for example:

broadeners=['Air', 'Self'],
ratios=[0.7, 0.3],

Legacy Alias: px.cross_section

Example

px.cross_sections(
    database='ExoMol',
    molecule='MgH',
    isotopologue='24Mg-1H',
    dataset='XAB',
    species_id=501,
    read_path='/path/to/ExoMol/',
    save_path='/path/to/output/',
    temperatures=[1000, 2000],
    pressures=[1.0],
    wn_wl='WN',
    wn_wl_unit='cm-1',
    min_range=0,
    max_range=30000,
    bin_size=0.1,
    abs_emi='Ab',
    abundance=1,
    profile='SciPyVoigt',
    device='GPU',
    gpu_backend='AUTO',
    gpu_batch_lines=8192,
    gpu_batch_grid=256,
    broadeners=['Default'],
    ratios=[1.0],
    cutoff=25.0,
    plot=True,
    plot_method='log',
)

---

px.stick_spectra_cross_section

px.stick_spectra_cross_section(inp_filepath=None, **kwargs)

Calculate LTE or Non-LTE stick spectra and cross sections simultaneously.

Parameters

All parameters from px.stick_spectra and px.cross_sections.

The same wn_wl/wn_wl_unit selection is used for both saved outputs: .stick and .xsec first columns are both wavenumber for WN and wavelength for WL. Cross-section bin_size follows the same unit.

Example

px.stick_spectra_cross_section(
    database='ExoMol',
    molecule='MgH',
    isotopologue='24Mg-1H',
    dataset='XAB',
    species_id=501,
    read_path='/path/to/ExoMol/',
    save_path='/path/to/output/',
    temperatures=[1000, 2000],
    pressures=[1.0],
    wn_wl='WN',
    wn_wl_unit='cm-1',
    min_range=0,
    max_range=30000,
    bin_size=0.1,
    abs_emi='Ab',
    abundance=1,
    profile='SciPyVoigt',
    device='GPU',
    gpu_backend='AUTO',
    gpu_batch_lines=8192,
    gpu_batch_grid=256,
    plot=True,
)