Here, we show that silicon dioxide molecules (SiO2) and silicon monoxide (SiO) can be efficiently formed by low-temperature gas-phase chemistry, even at 10 K. We report the results of combined crossover molecular beam studies and electronic structure calculations for the reaction of D1-silyl radicals (SiD; X2Π) with molecular oxygen (O2, X3Σg−) to form SiO2 and SiO27 through barrier-free reactions. This system represents the reaction of silyl radicals (SiH) generated by the photolysis of silane (SiH4)28,29,30 with O2 to synthesize silica via a single collision event. In the ISM, the reaction of SiH with O2 may represent a potential pathway for the formation of SiO2 and silicon oxides in these molecular clouds, where gas-phase chemistry follows sublimation of the ice mantle; these silicon oxides may drive exothermic chemical reactions that may generate larger The silica 25, 31 eventually forms silicates at low temperatures sio compound name
Reaction scattering experiments were performed using a crossed molecular beam setup (Methods). We monitored the scattering signals at mass-to-charge ratios (m/z) 62 (28SiDO2+), 60 (28SiO2+), and 44 (28SiO+). No signal was observed at m/z 62, suggesting that under single-collision conditions, the lifetime of the 28SiDO2 adduct is shorter than its flight time to the electron impact ionizer. A reactive scattering signal was detected at m/z 60 (28SiO2+) (Figure 1). The scatter signal is relatively weak, and up to 6 × 106 time-of-flight (TOF) spectra per angle (60 h collection time) must be averaged to obtain a reasonable signal-to-noise ratio. Signal detection at m/z 60 alone provides conclusive evidence for the formation of a molecule with the molecular formula 28SiO2 by a single collision event of two neutral reactants. Considering the data accumulation time, the signal-to-noise ratio obtained at m/z 60, and the abundances of the natural silicon isotopes 30Si (3.10 %), 29Si (4.67 %) and 28Si (92.23 %), we would not expect—as the experimental As evidenced - any reactive scattering signal at m/z 62 (30SiO2+). Finally, m/z 44 background counts in the detector from singly ionized carbon dioxide (CO2) precluded identification of any reactive scattering signal at m/z 44 (28SiO+). Altogether, the laboratory data indicate that in the reaction of SiD radicals with O2, molecular and atomic deuterium with the formula 28SiO2 (hereinafter: SiO2) are formed under single collision conditions.