极紫外光源及高荷态离子诱导下甲烷的脱氢通道碎裂机制  

Fragmentation mechanism of methane dehydrogenation channel induced by extreme ultraviolet and high charge ions

作　　者：骆炎 余璇 雷建廷 陶琛玉 张少锋[2,3] 朱小龙 马新文[2,3] 闫顺成 赵晓辉[1] Luo Yan;Yu Xuan;Lei Jian-Ting;Tao Chen-Yu;Zhang Shao-Feng;Zhu Xiao-Long;Ma Xin-Wen;Yan Shun-Cheng;Zhao Xiao-Hui(School of Physics Science and Technology,Hebei University,Baoding 071002,China;Institute of Mordern Physics,Chinese Academy of Sciences,Lanzhou 730000,China;University of Chinese Academy of Sciences,Beijing 100049,China;School of Nuclear Science and Technology,Lanzhou University,Lanzhou 730000,China)

机构地区：[1]河北大学物理科学与技术学院,保定071002 [2]中国科学院近代物理研究所,兰州730000 [3]中国科学院大学,北京100049 [4]兰州大学核科学与技术学院,兰州730000

出　　处：《物理学报》2024年第4期144-150,共7页Acta Physica Sinica

基　　金：国家重点研发计划(批准号:2022YFA1602500);国家自然科学基金(批准号:11934004,11974358)资助的课题.

摘　　要：CH_(4)广泛存在于行星大气之中,研究CH_(4)的解离动力学对了解宇宙中气体演化的过程具有重要的价值.目前,CH_(4)^(2+)→CH_(3)^(+)+H^(+)碎裂通道已被大量研究,但针对该通道的解离机制的解释尚存在一定争议.本实验利用高分辨反应显微成像谱仪,开展了25—44 eV的极紫外(extreme ultraviolet,XUV)光电离实验及1 MeV Ne^(8+)与CH_(4)的碰撞实验.通过符合测量得到了CH_(3)^(+)和H^(+)两种离子的动能,重构了两体解离的动能释放(kinetic energy release,KER),并研究了CH_(4)^(2+)解离产生CH_(3)^(+)+H^(+)解离路径下的碎裂动力学过程.在光电离实验中,观测到KER谱上存在4.75 eV和6.09 eV两个峰,结合前人的工作及XUV的能量范围,对每个峰的机制归属进行讨论.特别是4.75 eV峰,分析认为可能来自于CH_(4)^(2+)直接解离机制的贡献.另外,在1 MeV Ne^(8+)离子碰撞实验中,可观测到3个KER峰,将每个峰的分支比与以往的实验结果进行对比,未发现速度效应对KER谱的显著影响.CH_(4)is abundant in planetary atmosphere,and the study of CH_(4)dissociation dynamics is of great importance and can help to understand the atmospheric evolution process in the universe.At present,the CH_(4)^(2+)→CH_(3)^(+)+H^(+)channel has been extensively studied,but the explanation of the dissociation mechanism for this channel is controversial.In this work,the double-photoionization experiment of CH_(4)by extreme ultraviolet photon(XUV)in an energy range of 25-44 eV and the collision experiment between 1 MeV Ne^(8+)and CH_(4)are carried out by using the reaction microscope.The three-dimensional(3D)momenta of CH_(3)^(+)and H^(+)ions are measured in coincidence,the corresponding kinetic energy release(KER)is reconstructed,and fragmentation dynamics from the parent ion CH_(4)^(2+)to the CH_(3)^(+)+H^(+)ion pair are investigated.In the photoionization experiment,two peaks in the KER spectrum are observed:one is located around 4.75 eV,and the other lies at 6.09 eV.Following the conclusions of previous experiments and the theoretical calculations of Williams et al.(Williams J B,Trevisan C S,Schöffler M S,et al.2012 J.Phys.B At.Mol.Opt.Phys.45194003),we discuss the corresponding mechanism of each KER peak.For the 6.09 eV peak,we attribute it to the CH_(4)^(2+)dissociation caused by the Jahn-Teller effect,because this value is consistent with the energy difference in energy between the CH_(4)^(2+)1E initial state and the CH_(3)^(+)/H^(+)final state involving the Jahn-Teller effect.For the 4.75 eV peak,we believe that it may come from the direct dissociation of CH_(4)^(2+)without contribution from the Jahn-Teller effect.More specifically,Williams et al.presented the potential energy curve for one C—H bond stretching to 8 a.u.,while other C—H bonds are fixed at the initial geometry of the CH_(4)molecule.In the reflection approximation,we infer that the extra energy is released from the internuclear distance of 8 a.u.to infinity.It is found that the KER is 4.7 eV,which is consistent with the experimental observa

关 键 词：极紫外光 动能释放 异构化 库仑爆炸 

分 类 号：O621.13[理学—有机化学]