利用离子-中性光解碎片符合成像研究离子光解动力学

Ion-Neutral Photofragment Coincidence Imaging of Photodissociation Dynamics of Ionic Species

本文对最近研制的低温离子阱-离子速度成像谱仪进行升级,实现了探测离子光解反应的离子产物和中性产物速度影像的符合探测.实验上利用自制的低温圆柱形离子阱对制备的离子样品进行富集和冷却.从离子阱中引出的离子束准直后进入一组电势切换电极和离子速度聚焦成像系统开展激光光解实验.利用一组新设计的离子引出、加速和聚焦电场,离子束可以被加速至4500 eV以上,使中性解离产物获得足够的平动能而被位置灵敏的影像探测器直接探测.本文利用Ar2+离子的355 nm光解反应对升级后的装置进行测试.结果表明,光解产生的中性Ar原子和Ar+离子产物的速度影像分辨率分别为厶v/vu4.6%和1.5%.

The recen tly cons true ted cryogenic cylindrical ion trap velocity map imaging spectrometer(CIT-VMI)has been upgraded for coincidence imaging of both ionic and neutral photofragments from photodissociation of ionic species.The prepared ions are cooled down in a homemade cryogenic cylindrical ion trap and then extracted for photodissociation experiments.Wi th the newly designed elec trie fields for extraction and acceleration,the ion beam can be accelerated to more than 4500 eV,which is necessary for velocity imaging of the neutral photofragments by using the position-sensitive imaging detect or.The setup has been tested by the 355 nm pho todissocia tion dynamics of the argon dimer cat ion(Ar2+).From the recorded experimen tal images of both neu tral Ar and ionic Ar+fragments,we interpret velocity resolutions of△v/vu4.6%for neutral fragments,and△v/vul.5%for ionic fragments,respectively.