Adapt Adsorption Energies (Eads) for your model

The species freeze-out and thermal evaporation depend strongly on the value of the adsorption (aka desorption) energy. Those values are often re-evaluated (theoretically or in laboratory measurements) with sometimes large changes compared to previously accepted values. One can test the effects of such changes on the overall disk thermal structure and or the location of the freeze-zone by changing Eads.

The default adsorption energies can be found in the Reactions.in (or Reactions.in.csv) file. The adsorption energies in Kelvin are placed as the third value (in Reactions.in):

 287 H2O     FORM            H2O#                            0.00E+00  0.00       0.0000
 288 H2O#    DESTH           H2O                             0.00E+00  0.00    5700.0000    GH06
 289 H2O#    DESCR           H2O                             0.00E+00  0.00    5700.0000    GH06
 290 H2O#    DESPH           H2O                             0.00E+00  0.00    5700.0000    GH06

or in the Reactions.in.csv file

1268,IC,H2O,dust,,H2O#,dust,,,0.00E+00,+0.00000,0.0000,L,10,41000,B,
1269,DT,H2O#,dust,,H2O,dust,,,0.00E+00,+0.00000,5700.0000,L,10,41000,B,GH06

here for water the adsorption energy is 5700K. The reaction with

  • FORM or dust designates the freeze-out reactions
  • DESTH (DT) the thermal desorption reactions (Eads values can vary substantially in the literature, please cite the relevant papers if it impacts your results significantly)
  • DESCR the cosmic-ray induced desorption reactions (the standard Hasegawas and Herbst prescription is used here)
  • DESPH the photodesorption reactions (without existing cross-sections from e.g. the Leiden photodissociation database, a typical value will be assumed)

However, one can overwrite those values using a personal set of values. Three extra set of values can be found in the data/ChemicalNetwork directory:

Those files have to be copied to the directory of the ProDiMo run/model (i.e. into the same directory as the Parameter.in).

In Parameter.in

.true.           ! Eads_from_file : use private adsorption energies
Eads_Penteado.in ! Eads_filename  : use Penteado et al. values

N.B. One can only OVERWRITE the Eads values. Eads values in Reactions.in will be used if they are not in the Eads file. If the freeze-out/desorption reactions are not in the Reactions.in file, one has to manually edit the file and ADD the relevant reactions. Future work would include automatic creation of the reactions if the ice species is in Species.in and one use Eads from file.

Data format of the private Eads file

Lines starting with # are comments and will not be taken into account. The first column is the name of the gas species (C will freeze as C#). The second column (minimum of 1 whitespace to separate the second column from the first) is the Eads values in Kelvin. There is no need to write down the number of entries. Below I show the first two entries for Eads_Penteado.in. The user can create a private Eads file and name it arbitrarily, given there is no conflict with the name of the standard files required to run ProDiMo.

# Table 3 from Penteado E.M., Walsh C., Cuppen H.M. The Astrophysical Journal, Volume 844, Number 1, 2017
C             715.
C2           1085.

The name has to be the same than in the Species.in file and the temperatures are in Kelvins.

Please cite the specific article(s) where the new Eads values are taken from in your publications.