中能Ne^(4+)离子诱导的羰基硫分子三体碎裂动力学分析  

Three-body fragmentation dynamics of OCS^(3+) induced by intermediate energy Ne^(4+) ion impact

作　　者：申丽丽 闫顺成[1] 马新文[1] 朱小龙[1] 张少锋[1] 冯文天[1] 张鹏举[1] 郭大龙[1] 高永[1] 海帮 张敏[1,2] 赵冬梅 

机构地区：[1]中国科学院近代物理研究所,兰州730000 [2]中国科学院大学,北京100049

出　　处：《物理学报》2018年第4期61-67,共7页Acta Physica Sinica

基　　金：国家重点研发计划"大科学装置"重点专项(批准号:2017YFA0402300);国家自然科学基金(批准号:U1532129;11304325)资助的课题~~

摘　　要：利用反应显微成像谱仪开展了56 keV/u的Ne^(4+)离子与羰基硫(OCS)气体的交叉碰撞实验,研究了Ne^(4+)离子诱导的OCS^(3+)的碎裂动力学.通过符合探测三个末态离子,重构了OCS^(3+)离子三体碎裂对应的牛顿图和Dalitz图,并明确区分了直接解离和次序解离两种碎裂过程.重构了OCS^(3+)离子解离过程的动能释放(KER)分布,发现其峰值在25 eV处,同时在18 eV处有肩膀结构的存在,其中25 eV左右的峰来源于直接解离过程,18 eV处的肩膀结构来源于次序解离和非次序解离两种过程.通过分析不同能量和不同电荷态下重离子碰撞实验所得到的KER谱,发现微扰强度不是影响态布居的主要因素.OCS^(3+)次序解离中的第二步KER的峰值在6.2 eV处.结合以往的实验结果,我们得出结论:多电离态的分子发生次序碎裂的根源在于二价离子碎片存在亚稳态,而重构得到的第二步KER可以反映亚稳态离子的电子态信息.The fragmentation experiment of OCS^3＋ induced by 56 keV/u Ne4＋ ions is performed using reaction microscope, and the corresponding dissociation dynamics is investigated. By detecting the three fragment ions in coincidence, the three-dimensional （3D） momenta of all ions and the corresponding kinetic energy release （KER） distributions are reconstructed. It is found that a peak maximum of the KER distribution is locates at about 25 eV, and a shoulder structure appears around 18 eV. This result is consistent with previous heavy ion experimental results with different perturbation strengths. Taking into account that the KER distribution is related to the initial state population of the OCS^3＋ parent ions, it can be concluded that the perturbation strength is not a decisive parameter leading to the initial state population of OCS^3＋ ions. We also reconstruct the Newton diagram and Dalitz plot for the three-body fragmentation of OCS^3＋ ion, from which the sequential dissociation is distinguished from nonsequential dissociation clearly. By analyzing the kinetic energy of ions from each fragmentation process, we find that the KER peak at 25 eV corresponds to nonsequential dissociation process, but the shoulder at 18 eV arises from both sequential and nonsequential dissociation processes. This phenomenon suggests that the parent OCS^3＋ ions in ground state and low excitation states tend to fragment through sequential dissociation, while those in high excitation states tend to fragment through nosequential dissociation. Furthermore, we reconstruct the KER distributions in the second fragmentation step of sequential dissociation, whose peak maximum is at 6.2 eV, corresponding to X3Π, 1Σ＋ and 1Π metastable states of CO2＋ ion. A similar KER distribution is obtained for the second fragmentation step of the OCS^4＋ ion. By comparing our experimental results with previous ones, we conclude that the origin of sequential dissociation process is the existence of metastable state, and the reconstructed KER

关 键 词：羰基硫 碎裂机制 次序解离 动能释放 

分 类 号：O56[理学—原子与分子物理]