##Primordial environments##

The description of the following chemical processes and the related microphysics are useful for applications involving primordial environments where the dominant elementary species are mainly hydrogen and helium. Due to the low complexity of these environments the physical processes are well tested and the uncertainties well-established. Note: the chemical networks we propose here and the physical processes that we discuss should be only taken as a suggestion, we encourage users to improve it and to feel free to include additional processes they consider important.

Chemical networks

In Krome there are three "so-called" primordial chemical networks:

• react_primordial mostly based on Abel et al. 1997
• react_primordial2 based on Omukai 2000
• react_primordial3 an updated network which includes the most recent reaction rates

Here below we describe the main differences and the possible applications of the three networks.

Physical processes options