rizer.kinetics.electron_reactions#

Classification of electron-impact reactions.

Also computes their inelastic energy exchange with the electron/gas energy pools.

Classes#

ElectronicReactionEnergetics

Electron-impact reaction energetics for a plasma mechanism.

Functions#

load_curated_formation_enthalpy_0K(→ dict[str, float])

Load curated standard enthalpies of formation at 0 K, in J/kmol.

species_formation_enthalpy_0K(→ numpy.ndarray)

Return each species' \(H(0\,K)\) [J/kmol], for the reactions needed.

reaction_involves_electron(→ bool)

Return True if the electron participates in reaction.

electron_reaction_indices(→ numpy.ndarray)

Return the indices of the electron-impact reactions in plasma.reactions().

species_h0k_for_mechanism(→ numpy.ndarray)

Return the species_h0k array to hand a native reactor's constructor.

Module Contents#

rizer.kinetics.electron_reactions.load_curated_formation_enthalpy_0K() → dict[str, float]#

Load curated standard enthalpies of formation at 0 K, in J/kmol.

Returns:

Species name -> \(\\Delta_f H^\\circ(0\\,K)\) [J/kmol].

Return type:

dict of str to float

Notes

Reads data/mechanisms/thermo/formation_enthalpy_0K.yaml, a curated, cited (ATcT/NIST) table covering the species used in this repo’s two production electron-impact mechanisms (air_plasma_Laux2000.yaml, Goutier2025/CH4_to_C2H2.yaml, including its excited-state phases), including the electron itself (on the thermal electron convention – see the file’s own description).

Cached (the file is static and file-shipped): callers must not mutate the returned dict, since every caller shares the same cached object.

rizer.kinetics.electron_reactions.species_formation_enthalpy_0K(plasma: cantera.Solution, electron_reaction_indices: numpy.ndarray) → numpy.ndarray#

Return each species’ \(H(0\,K)\) [J/kmol], for the reactions needed.

Parameters:
Returns:

\(H(0\,K)\) [J/kmol], length plasma.n_species.

Return type:

numpy.ndarray

Raises:

ValueError – If a heavy species with nonzero net stoichiometry in an electron-impact reaction has no entry in load_curated_formation_enthalpy_0K().

Notes

Only species that actually participate (nonzero net stoichiometry) in at least one electron-impact reaction get a real value; every other species is left at 0, which is safe since it is always multiplied by a zero net stoichiometric coefficient wherever the result is used (the electron-impact reaction rows of the net-stoichiometry matrix). This is shared by ElectronicReactionEnergetics (pure-Python reactor) and the Reactor0D/solve_channel_transient pybind11 bindings (C++ reactor), so both compute this fixed vector from the exact same logic.

rizer.kinetics.electron_reactions.reaction_involves_electron(reaction: cantera.Reaction, electron_name: str = 'e-') → bool#

Return True if the electron participates in reaction.

Detection is done on the reaction equation rather than on reaction.reactants / reaction.products (or the stoichiometric-coefficient matrices). Cantera cancels a spectator electron – one that appears on both sides with equal stoichiometry, as in the electron-impact dissociation/excitation reaction CH4 + e- => CH3 + H + e- – from those, so a membership test there misses such reactions even though they are electron-impact processes. The equation string keeps the electron as written, so it detects both spectator electrons and electrons produced/consumed net (ionization, recombination, attachment).

Parameters:

  • reaction (cantera.Reaction) – Reaction to test.

  • electron_name (str, optional) – Name of the electron species, by default "e-".

Returns:

Whether the electron appears in the reaction equation.

Return type:

bool

Notes

This is the exact Python twin of the C++ equationHasElectron in rizer/cantera_ext/models/nrp/ReactorRHS.cpp: both replace the reaction-arrow and stoichiometric-plus characters + = < > with spaces and then look for the electron as a standalone whitespace-delimited token. The two implementations MUST stay byte-for-byte equivalent so the native C++ reactor and this Python reference select the identical set of electron-impact reactions for the inelastic electron-to-gas power; change them together.

rizer.kinetics.electron_reactions.electron_reaction_indices(plasma: cantera.Solution) → numpy.ndarray#

Return the indices of the electron-impact reactions in plasma.reactions().

Parameters:

plasma (cantera.Solution) – Cantera plasma object.

Returns:

Indices i into plasma.reactions() for which reaction_involves_electron() is true.

Return type:

numpy.ndarray

Raises:

cantera.CanteraError – If plasma has no "e-" species. Without this check, a plasma missing the electron species would silently match zero reactions (equation-string matching, not a species lookup) instead of failing loudly, leaving inelastic power silently stuck at zero.

rizer.kinetics.electron_reactions.species_h0k_for_mechanism(mech: str, phase: str, reacting: bool, plasma: cantera.Solution | None = None) → numpy.ndarray#

Return the species_h0k array to hand a native reactor’s constructor.

Parameters:

  • mech (str) – Cantera mechanism (YAML) path and phase name.

  • phase (str) – Cantera mechanism (YAML) path and phase name.

  • reacting (bool) – Whether the reactor being built includes finite-rate chemistry.

  • plasma (cantera.Solution, optional) – Already-loaded Solution for mech/phase, reused (when reacting) instead of loading a second copy. If None, one is loaded here. Ignored if reacting is False.

Returns:

Per-species H(0K) [J/kmol] (see species_formation_enthalpy_0K()), or an empty array if not reacting – epsilon_th is only ever evaluated by the C++ side when reacting, so a non-reacting run never needs curated 0K data for species it will never use it for.

Return type:

numpy.ndarray

class rizer.kinetics.electron_reactions.ElectronicReactionEnergetics(plasma: cantera.Solution)#

Electron-impact reaction energetics for a plasma mechanism.

Precomputes reaction indices and stoichiometry needed to compute the inelastic electron-to-gas power exchange.

Parameters:

plasma (cantera.Solution) – Cantera plasma object.

plasma#
plasma_reactions: list[cantera.Reaction]#

List of the reactions in the plasma object.

plasma_power_inelastic() → float#

Return the inelastic Joule heating power per unit volume of the plasma in W/m^3.

Returns:

Inelastic Joule heating power density in W/m^3.

Return type:

float

Notes

The power density is given by equation 36 of [Aurora], using each electron-impact reaction’s fixed threshold energy in place of \(\Delta H_i\):

\[P_{inel} = \sum_{i}^{I_{ei}} \varepsilon_{th,i} \cdot R_i \qquad\text{with}\qquad \varepsilon_{th,i} = \sum_k \nu_{ki}\, H_k(0\,K)\]

with:

  • \(I_{ei}\) the number of electron-impact reactions, i.e. reactions in which the electron participates,

  • \(\varepsilon_{th,i}\) reaction \(i\)’s net enthalpy of formation at 0 K – a fixed threshold energy, independent of \(T_g\)/\(T_e\), precomputed once at construction (see load_curated_formation_enthalpy_0K()),

  • \(R_i\) the net rate of progress of reaction \(i\).

Since \(\varepsilon_{th}\) is added in the gas-energy equation and subtracted in the electron-energy equation (symmetrically, as with the elastic exchange term), combined (\(T_g\), \(T_e\)) energy conservation holds regardless of \(\varepsilon_{th}\)’s specific form: only the split of a reaction’s energy between the two pools depends on it, not the total. The heavy-species chemical term in the reactor still uses the state-dependent internal energy (each species’ partial molar internal energy at \(T_g\), summed over all reactions, not just electron-impact ones).

Electron-impact reactions are selected by testing whether the electron participates as a reactant or a product, rather than by matching a rate-type string. These are exactly the reactions that exchange energy between the electron energy pool and the internal/chemical energy of the heavy species, whatever their rate type (two-temperature-plasma, three-body-two-temperature-plasma, reverse-two-temperature-plasma, Druyvesteyn, janev-*, …). Selecting them by type string silently dropped every channel whose type was not one of the two-temperature ones.