= Nitrogen–ammonia quenching
{title2=$\mathrm{N}_2\rightleftharpoons\mathrm{NH}_3$ quenching}
<Nitrogen–ammonia quenching> occurs when transport preserves a nonequilibrium partition between <molecular nitrogen> and <Ammonia>. Their net conversion may be written
$$
\mathrm{N}_2+3\mathrm{H}_2\rightleftharpoons2\mathrm{NH}_3,
$$
but its actual relaxation time depends on a multistep reaction network. Near a <chemical quench level>, that time exceeds the <eddy mixing time>, so the abundance can retain a deeper value instead of following local <thermochemical equilibrium>.
Coupled diffusion and chemistry models illustrate ammonia enhancement by transport and destruction at high altitudes by <atmospheric photochemistry>.<Disequilibrium Carbon, Oxygen, and Nitrogen Chemistry in the Atmospheres of HD 189733b and HD 209458b by Julianne I. Moses and others>[Abstract: ammonia mole fractions and the distinct effects of mixing and photochemistry]{ref} Interpreting an ammonia feature therefore requires an <atmospheric pressure-temperature profile> and a transport model, not only a molecular identification.
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