Hydrogen as a coolant

To include the Hydrogen atom as a coolant, in particular the bound-free and bound-bound emission, one needs to activate this switch

.true.       ! Hatom_bf

which will automatically also activate the bound-bound transitions (switch Hatom_bb). Please note that one has to also active the UVpumping switch to use the large H atom model.

For hydrogen with Hatom_bf, it is necessary to include an EUV radiation field (from the star). This can be done by setting

0.0136      ! Xray_Emin

This implies that Xrays are also activated in the model. As an alternative, one can also provide a custom StarSpectrum.in.

If you are not using a recent version of the default Reactions.in.csv, you might have to add the following reaction (from Janev & Smith 1993) to your Reactions.in.csv.

3727,IN,H,e-,,H+,e-,e-,,4.30E-10,0.636,157462.0,L,3000,500000 B,Janev&Smith (1993)

If the reaction is missing, the code will stop at some point.

Some more details, and an example where it was necessary to include this, can be found in Backs+ (2023), which should also be cited if you use those switches.

Large H atom

The default H model includes only about 40 transitions, which is fine for lines up to the mid-infrared. To study H lines at longer wavelengths or to just have a more complete H model one can use the Custom molecule/lines feature. For example to use a H atom with 19900 transition just create a LineSelection.in file in your model directory with this content:

*** use a very large H atom model with 200 levels.
H                       ! name   : select the coolant/SYS by name here H
Hatom_200full_lamda.dat ! file   : provide a file name, here LAMDA format, file is part of the ProDiMo source distribution

To create this Lamda file we used the code RADZ1, and an approximate method to calculate collision rates with e- (same method as was used in Backs+ (2023)).

TODO: Maybe some more details (origin, is there a better ProDiMo paper to cite, maybe look in the code or ask Peter)

Ly alpha escape

For the Ly alpha ProDiMo can use the assumption of Lyman resonance scattering to exit (pesc=1 for u=2 and l=1). This can be controlled by the switch

.false.   ! Lyalpha_perfect_escape  : Lyman resonance scattering to exit assumption

It seems for most disk models setting this to .false. is the better option. However, it is probably good to make some test for your model.