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 (SiO2) along
with silicon monoxide (SiO) can be synthesized via the reaction of the silylidyne radical (SiH) with molecular oxygen (O2) 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.
图1 交叉分子束装置。激光消融法产生Si并与D2反应生成SiD (X2Π)，并进一步与O2交叉碰撞反应，生成产物通过低温可旋转质谱过滤型装置探测，获得实验室坐标系下产物的飞行时间谱与角度强度分布
图2 SiH与O2的反应势能面图。由于实验系统约束，无法产生基态SiH分子束源，但SiD-O2与SiH-O2系统在整个势能面上的反应物、中间物、产物能量相差均小于3 kJ mol-1，故对实验结果无重要影响
