Interstellar hydrides—that is, molecules containing a single heavy element atom with one or
more hydrogen atoms—were among the first molecules detected outside the solar system.
They lie at the root of interstellar chemistry, being among the first species to form in initially
atomic gas, along with molecular hydrogen and its associated ions. Because the chemical
pathways leading to the formation of interstellar hydrides are relatively simple, the analysis
of the observed abundances is relatively straightforward and provides key information about�…