Characterize silane chemistry and quenching in hydrogen-rich envelopes

Characterize the reaction kinetics and rate-limiting pathways governing silane decomposition and silicon-carbide formation in dense, highly reducing hydrogen-dominated sub-Neptune envelopes, and determine the resulting silane quench pressures and observable abundances.

Background

The predicted visibility of SiH$_4$ depends sensitively on whether silane is removed through SiC condensation before atmospheric transport quenches the chemistry. Existing kinetic measurements were obtained in neutral gases or semiconductor-processing environments rather than in the dense, reducing hydrogen atmospheres relevant to sub-Neptunes.

The paper notes that SiC formation may proceed through multiple reactions, so silane decomposition may not be the rate-limiting step. Consequently, current quench-pressure estimates and predictions for silane spectral features remain uncertain.