http://prl.aps.org/abstract/PRL/v110/i10/e103601）上。他们在自建的国际先进的强场原子分子光物理实验平台上，全微分符合测量了飞秒强激光场下二氧化碳三价离子三体解离产生的所有碎片离子的三维动量，通过发展两个氧原子离子的能量关联图，首次将强激光场下二氧化碳三价离子的非序列解离（两个C=O键同时断裂）和序列解离（两个C=O键分步断裂）通道的实验数据区分开来。结合三体解离动力学的理论模拟，精确重构出二氧化碳三价离子解离前的分子构型，再现了激光作用前中性二氧化碳分子的构型。这是继强激光场下原子分子隧道电离研究入选“2012年度中国高等学校十大科技进展”（http://pkunews.pku.edu.cn/xxfz/2012-12/19/content_261328.htm）后，他们在自建的强场原子分子物理实验平台上取得的又一重要进展。
论文第一作者是博士生吴聪同学，他在三体符合实验测量以及数据处理方面做出了重要贡献。本研究工作得到了科技部重大科学研究计划、国家自然科学基金委以及国家重点实验室的资助。
Nonsequential and sequential fragmentation of CO23+in intense laser fields
Investigating transient molecular structure is one of the fundamental tasks in physics, chemistry and biology. Femtosecond laser coulomb explosion imaging has been exhibited to be a feasible approach to monitoring transient molecular structure, in which the molecule is rapidly ionized by intense femtosecond laser field and the multiply charged molecular ion is quickly fragmented. The molecular structure is then deduced from momentum vectors of correlated fragments. However, this method still remains challenging for polyatomic molecules because of their complicated fragmentation dynamics. The main question lies in whether the chemical bonds break through a sequential or a non-sequential process.
Very recently, Prof. Chengyin Wu, Prof. Qihuang Gong et al systematically studied three-body fragmentation dynamics of carbon dioxide tri-cation in intense femtosecond laser fields. Three-dimensional momenta were precisely acquired for the three correlated atomic ions through three-body coincidence measurement. Non-sequential and sequential fragmentation ofcarbon dioxide tri-cation were precisely separated and unambiguously identifiedby developing kinetic energycorrelation diagram and Newton plot. With the high-level ab initio potential of carbon dioxide tri-cation and accurate three-dimensional momentum vectors of the atomic ions, the geometric structure of carbon dioxide tri-cation before fragmentationwas reconstructed, which turns out to be close to that of the neutral carbon dioxide molecule before laser irradiation. The study indicated that Coulomb explosion is a promising approach to imaging geometric structures of polyatomic molecules if the fragmentation dynamics can be clearly clarified and the accurate dissociation potential is provided for multiply charged molecular ions.The work has been published by the Phys. Rev. Lett. (C. Wu et al“Nonsequential and sequential fragmentation of CO23+in intense laser fields”, Phys. Rev. Lett. 110, 103601 (2013), http://prl.aps.org/abstract/PRL/v110/i10/e103601).
