Directed gas phase formation of silicon dioxide and implications for the formation of interstellar silicates

Interstellar silicates play a key role in star formation and in the origin of solar systems, but their synthetic routes have remained largely elusive so far. Here we demonstrate in a combined crossed molecular beam and computational study that silicon dioxide (SiO 2 ) along with silicon monoxide (SiO) can be synthesized via the reaction of the silylidyne radical (SiH) with molecular oxygen (O 2 ) under single collision conditions. This mechanism may provide a low-temperature path—in addition to high-temperature routes to silicon oxides in circumstellar envelopes—possibly enabling the formation and growth of silicates in the interstellar medium necessary to offset the fast silicate destruction. Interstellar silicates play a key role in star formation, however their synthetic routes are not fully understood. Here, the authors provide evidence for the formation of SiO 2 along with SiO via low-temperature gas phase chemistry.