Henry's Law phase-trasfer reactions use equilibrium rate constants that are calculated as:

\[ HLC(298K) * e^{C({1/T-1/298})} \]

where \(HLC(298K)\) is the Henry's Law constant at 298 K [M \(\mbox{Pa}^{-1}\)], \(C\) is a constant [K] and \(T\) is the temperature [K]. Uptake kinetics are based on the particle effective radius, \(r_{eff}\) [ \(\mbox{m}\)], the condensing species gas-phase diffusion coefficient, \(D_g\) [ \(\mbox{m}^2\,\mbox{s}^{-1}\)], its molecular weight \(MW\) [kg \(\mbox{mol}^{-3}\)], and \(N^{*}\), which is used to calculate the mass accomodation coefficient.

Mass accomodation coefficients and condensation rate constants are calculated using the method of Ervans et al. (2003) [Ervens2003] and references therein. Mass accomodation coefficients ( \(\alpha\)) are calculated as:

\[ \Delta H_{obs} = -10 \times (N^*-1) + 7.53 \times (N^{*2/3}-1) - 0.1 \times 10 \quad (\mbox{kcal}\,\mbox{M}^{-1}) \]

\[ \Delta S_{obs} = -13 \times (N^*-1) - 19 \times (N^*-1) + 9.21 \times (N^{*2/3}-1) - 0.1 \times 13 \quad (\mbox{cal}\,\mbox{M}^{-1}\,\mbox{K}^{-1}) \]

\[ \frac{\alpha}{1-\alpha} = e^{\frac{-\Delta G^{*}}{RT}} \]

If \(\Delta H\) and \(\Delta S\) are not provided, \(\alpha\) is set to 0.1 [Zaveri2008].

Condensation rate constants are calculated following [Zaveri2008] as:

\[ k_c = 4 \pi r D_g f_{fs}( K_n, \alpha ) \]

where \(r\) is the radius of the particle(s) [m], \(D_g\) is the diffusion coefficient of the gas-phase species [ \(\mbox{m}^2\,\mbox{s}^{-1}\)], \(f_{fs}( K_n, \alpha )\) is the Fuchs Sutugin transition regime correction factor [unitless], \(K_n\) is the Knudsen Number [unitess], and \(\alpha\) is the mass accomodation coefficient.

Rates can be calculated as:

\[ r_c = [G] N_a k_c \]

where \([G]\) is the gas-phase species concentration [ppm], \(N_a\) is the number concentration of particles [ \(\mbox{particle}\,\mbox{m}^{-3}\)] and the rate \(r_c\) is in [ \(\mbox{ppm}\,\mbox{s}^{-1}\)]. The particle radius used to calculate \(k_{f}\) is the effective radius [ \(r_{eff}\)], which is taken as the "least-wrong" choice for condensation rates, as it is weighted to surface area [Zender2002] .

Input data for Phase transfer equations have the following format :

{
  "type" : "HL_PHASE_TRANSFER",
  "gas-phase species" : "my gas spec",
  "aerosol-phase species" : "my aero spec",
  "areosol phase" : "my aqueous phase",
  "aerosol-phase water" : "H2O_aq",
    ...
}

The key-value pairs gas-phase species, and aerosol-phase species are required. Only one gas- and one aerosol-phase species are allowed per phase-transfer reaction. Additionally, gas-phase species must include parameters named HLC(298K) [M Pa-1], which is the Henry's Law constant at 298 K, HLC exp factor [K], which is the Henry's Law constant exponential factor "C", diffusion coeff [m2 s-1], which specifies the diffusion coefficient in \(\mbox{m}^2\,\mbox{s}^{-1}\), and molecular weight [kg mol-1], which specifies the molecular weight of the species in \(\mbox{kg}\,\mbox{mol}^{-1}\). They may optionally include the parameter N star, which will be used to calculate the mass accomodation coefficient. When this parameter is not included, the mass accomodation coefficient is assumed to be 1.0.