Extend gas list

[nichollsh]

SOCRATES has a pre-defined list of gases. However, it this list is currently missing some species of interest that we plan to incorporate into new spectral files, for current and future science projects. See issue #8.

I propose adding the relevant gases to the SOCRATES codebase to support these projects. I believe we can do this liberally, because there's almost zero computational overhead to adding them to the code. Changes can also be synced to the original MetOffice SOCRATES repo to prevent future divergence problems.

This involves updating the following files:

• julia/src/SOCRATES_C.f90
• julia/src/SOCRATES.jl
• spectraltools/src/phys.py
• spectraltools/src/utils.py
• src/interface_core/socrates_set_spectrum.F90
• src/modules_gen/input_head_pcf.f90
• src/radiance_core/def_control.F90
• src/radiance_core/gas_list_pcf.F90

Proposed gas list extension:

Si
SiO
SiO2
Mg
Mg2
MgO
TiO2
Fe
FeO
Ca
CaO
AlO
Na2
NaO
NaOH
KOH
H-
PS
PO
PN
CH3SH
CH3S
C2H6S
C2H6S2
C3H4
C4H3
C2H4
SiH4
S2
SF6
CS2
S8
CN
CH3Cl
CH3F
CH3Br

@timlichtenberg @leojola suggestions?

[leojola]

that's a fantastic add on to PROTEUS! I am excited to see this! I would suggest to add CN as well (a strong optical and UV absorber) and the alkalis K and Na. Less of a priority but good to have could also be Fe and TiO.

[timlichtenberg]

Looks like a very good list to me. Honestly I do not know right now which other species could be important. This roughly covers "lava planets", "miscible sub-Neptunes", and "prebiotic Earth" regimes, right?

[nichollsh]

that's a fantastic add on to PROTEUS! I am excited to see this! I would suggest to add CN as well (a strong optical and UV absorber) and the alkalis K and Na. Less of a priority but good to have could also be Fe and TiO.

Thanks, Leoni. I'll add CN to the list, and the others you mention are already supported by SOCRATES.

[timlichtenberg]

Here's some additional researched list according to the priorities I mentioned above, with some notable additions:

• TiO2: already in AGNI's vaps_standard but has no SOCRATES gas ID. Important for lava planets according to Zilinskas+
• CaO: visible/near-IR electronic transitions. Ca is the third most abundant rock-forming cation after Si and Mg
• Ca (atomic): Ca II H&K lines (393/397 nm) are strong UV/blue absorbers in silicate vapor atmospheres
• AlO: visible electronic transitions. Completes the major rock-forming oxide set (Si, Mg, Fe, Ca, Al)
• NaOH, KOH: mid-IR absorbers, important Na/K sinks when hydrogen is present
• C2H4 (ethylene): already in AGNI, photochemical product of CH4, potential biosignature
• CH3Cl: biosignature gas (9.8 um), potentially important for M-dwarfs rockies

[nichollsh]

Fantastic - thanks for this too. C2H4 is already supported but the rest are new. CH3Br and CH4F are also biosignature gases.