Chemical Reaction Rates

Class providing rates for chemical reactions among gas-phase species (e.g.H\(_2\) formation and photodissociation, HD, HeH\(^+\)). Given local conditions—column density for self-shielding, gas temperature, chemical abundances, a clumping factor, and the ambient radiation field—each implementation returns the net reaction rates (in consistent volumetric units) for each tracked chemical species. These rates drive the non-equilibrium evolution of the chemical network and are particularly relevant for modeling the formation of molecular gas and cooling in the early universe and in low-metallicity IGM gas.

Default implementation: chemicalReactionRateZero

Methods

rates → void

Return the collisional excitation cooling rate , in units of J/m\(^3\)/s, for ion of given atomicNumber and electronNumber at temperature T (in Kelvin).

  • double precision , intent(in ) :: lengthColumn , temperature

  • type (chemicalAbundances ), intent(in ) :: chemicalDensity

  • double precision , intent(in ) :: factorClumping

  • class (radiationFieldClass), intent(inout) :: radiation

  • type (chemicalAbundances ), intent(inout) :: chemicalRates

  • type (treeNode ), intent(inout) :: node

chemicalReactionRateHydrogenNetwork

A chemical reaction rate class that computes rates using the network of reactions and fitting functions from Abel et al. (1997) and Tegmark et al. (1997). The parameter [fast] controls the approximations made. If set true then H\(^-\) is assumed to be at equilibrium abundance, H\(_2^+\) reactions are ignored and other slow reactions are ignored (see Abel et al. 1997).

Methods

  • rateH_Electron_to_Hplus_2Electron — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H} + \hbox{e}^- \rightarrow \hbox{H}^+ + 2\hbox{e}^-\).

  • rateHplus_Electron_to_H_Photon — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H}^+ + \hbox{e}^- \rightarrow \hbox{H} + \gamma\).

  • rateH_Electron_to_Hminus_Photon — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H} + \hbox{e}^- \rightarrow \hbox{H}^- + \gamma\).

  • rateH_Hminus_to_H2_Electron — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H} + \hbox{H}^- \rightarrow \hbox{H}_2 + \hbox{e}^-\).

  • rateH_Hplus_to_H2plus_Photon — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H} + \hbox{H}^+ \rightarrow \hbox{H}_2^+ + \gamma\).

  • rateH2plus_H_to_H2_Hplus — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H}_2^+ + \hbox{H} \rightarrow \hbox{H}_2 + \hbox{H}^+\).

  • rateH2_Hplus_to_H2plus_H — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H}_2 + \hbox{H}^+ \rightarrow \hbox{H}_2^+ + \hbox{H}\).

  • rateH2_Electron_to_2H_Electron — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H}_2 + \hbox{e}^- \rightarrow 2\hbox{H} + \hbox{e}^-\).

  • rateH2_H_to_3H — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H}_2 + \hbox{H} \rightarrow 3\hbox{H}\).

  • rateHminus_Electron_to_H_2Electron — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H}_2^+ + \hbox{H} \rightarrow \hbox{H}_2 + \hbox{H}^+\).

  • rateHminus_H_to_2H_Electron — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H}^- + \hbox{H} \rightarrow 2 \hbox{H} + \hbox{e}^-\).

  • rateHminus_Hplus_to_2H — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H}_2^+ + \hbox{H} \rightarrow \hbox{H}_2 + \hbox{H}^+\).

  • rateHminus_Hplus_to_H2plus_Electron — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H}^- + \hbox{H}^+ \rightarrow \hbox{H}_2^+ + \hbox{e}^-\).

  • rateH2plus_Electron_to_2H — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H}_2^+ + \hbox{e}^- \rightarrow 2\hbox{H}\).

  • rateH2plus_Hminus_to_H2_H — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H}_2^+ + \hbox{H}^- \rightarrow \hbox{H}_2 + \hbox{H}\).

  • rateH_Gamma_to_Hplus_Electron — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H} + \gamma \rightarrow \hbox{H}^+ + \hbox{e}^-\).

  • rateHminus_Gamma_to_H_Electron — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H}^- + \gamma \rightarrow \hbox{H} + \hbox{e}^-\).

  • rateH2_Gamma_to_H2plus_Electron — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H}_2 + \gamma \rightarrow \hbox{H}_2^+ + \hbox{e}^-\).

  • rateH2plus_Gamma_to_H_Hplus — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H}_2^+ + \gamma \rightarrow \hbox{H} + \hbox{H}^+\).

  • rateH2plus_Gamma_to_2Hplus_Electron — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H}_2^+ + \gamma \rightarrow 2\hbox{H}^+ + \hbox{e}^-\).

  • rateH2_Gamma_to_H2star_to_2H — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H}_2^+ + \gamma \rightarrow 2\hbox{H}^+ + \hbox{e}^-\).

  • rateH2_Gamma_to_2H — Computes the rate (in units of cm\(^{-3}\) s\(^{-1}\)) for the reaction \(\hbox{H}_2 + \gamma \rightarrow 2\hbox{H}\).

Parameters

  • [fast] (default .true.) — Specifies whether or not to use simplifying assumptions to speed the hydrogen network calculation. If true, H\(^-\) is assumed to be at equilibrium abundance, H\(_2^+\) reactions are ignored and other slow reactions are ignored (see Abel et al. 1997).

  • [includeSelfShielding] (default .false.) — If true, include estimates of self-shielding when computing reaction rates involving the radiation field.

chemicalReactionRateZero

A null implementation of the chemical reaction rate class that returns zero rates for all reactions and all chemical species. Useful for disabling chemistry while testing other physical processes or in models that do not require chemical evolution.

(Default implementation)