氦原子碰撞诱导解离表征原子团簇上小分子的吸附

Characterization of adsorption of small molecules over atomic clusters through collisions with helium beam

研究原子团簇上小分子的吸附和反应对认识一些复杂化学过程的微观机理非常重要,为了表征小分子如何吸附在原子团簇上,我们研制了一套氦原子碰撞诱导解离串级飞行时间质谱装置.该装置配有激光溅射团簇源,团簇在快速流动管里与一氧化碳、水等小分子发生反应,产物团簇通过第一级飞行时间质谱"选质"后与一束氦气(He)发生碰撞,使用第二级飞行时间质谱检测碰撞碎片的分布.结果表明:一些过渡金属氧化物团簇上小分子的弱吸附、强吸附以及氧化性吸附能够通过该实验装置进行表征.

Study of adsorption and reaction of small molecules over atomic clusters are very important to understand molecular level mechanisms of complex chemical processes.To characterize how small molecules may be absorbed over atomic clusters,a time-of-flight （TOF）/TOF tandem mass spectrometer （MS） employing collision-induced dissociation （CID） with helium atoms has been built.This apparatus is equipped with a laser ablation cluster source.The generated clusters react in a fast flow tube with small molecules such as carbon monoxide,water and so on.The product clusters are mass-selected by the primary TOF-MS and collided with a crossed helium beam.The secondary TOF-MS is used to detector the fragment ion distribution upon the collision.The results indicate that the apparatus can be used to characterize weak adsorption,strong adsorption,and oxidative adsorption over some transition metal oxide clusters.