We aimed to build a new and updated C0-C2 chemical network to study the CHON
disequilibrium chemistry of warm and hot exoplanet atmospheres that relies on
extensively validated and recent state-of-the-art combustion networks. The
reliability range of this network was aimed for conditions between 500 - 2500 K
and 100 - 10^-6 bar. ...
We aimed to build a new and updated C0-C2 chemical network to study the CHON
disequilibrium chemistry of warm and hot exoplanet atmospheres that relies on
extensively validated and recent state-of-the-art combustion networks. The
reliability range of this network was aimed for conditions between 500 - 2500 K
and 100 - 10^-6 bar. We compared the predictions of seven networks over a large
set of experiments, covering a wide range of conditions (pressures,
temperatures, and initial compositions). To examine the consequences of this
new chemical network on exoplanets atmospheric studies, we generated abundances
profiles for GJ 436 b, GJ 1214 b, HD 189733 b, and HD 209458 b, using the 1D
kinetic model FRECKLL and calculated the corresponding transmission spectra
using TauREx 3.1. These spectra and abundance profiles have been compared with
results obtained with our previous chemical network. Our new kinetic network is
composed of 174 species and 1293 reactions mostly reversible. This network
proves to be more accurate than our previous one for the tested experimental
conditions. The nitrogen chemistry update is found to be impactful on the
abundance profiles, particularly for HCN, with differences up to four orders of
magnitude. The CO2 profiles are also significantly affected, with important
repercussions on the transmission spectrum of GJ 436 b. These effects highlight
the importance of using extensively validated chemical networks to gain
confidence in our models predictions. As shown with CH2NH, the coupling between
carbon and nitrogen chemistry combined with radicals produced by photolysis can
have huge effects impacting the transmission spectra.