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原子团簇的激发温度可由反应产物(出射电子或碎片)的初始平动能这一可观测量间接获得,为了提高原子团簇激发温度的测量精度,设计并搭建了一套具有高动能分辨的离子速度成像谱仪。本谱仪的高动能分辨性能首先借助Simion8.0软件优化静电透镜和分子束限束装置的几何结构来实现,然后通过理论模拟证明本套谱仪具有预期好的动能分辨能力。设备搭建完成后,研究了C60分子束在纳秒激光场中发生的延迟电离过程,获得了C_(60)~+离子随延迟时间增加而逐渐变窄的二维时间切片图像。分析表明,激光脉冲产生的多个C_(60)~+离子间的库仑耦合作用将会扩展二维切片图像的横向分布,提取库仑耦合作用对C_(60)~+离子初始平动能的影响,并通过分析C_(60)~+离子间的库仑耦合随延迟时间增加而逐渐变弱的定量依赖关系,证实了本套谱仪具有了设计预期的高动能分辨能力。这一工作为下一步基于离子速度成像技术细致研究分子热力学的相关课题提供技术参考。
The ignition temperature of atomic clusters can be indirectly obtained from the observability of the initial translational energy of the reaction product (exiting electrons or fragments). In order to improve the measurement accuracy of atomic cluster excitation temperature, a set of ion velocity imaging spectroscopy with high kinetic energy resolution instrument. The high kinetic energy resolution performance of the spectrometer is firstly optimized by using Simion8.0 software to optimize the geometry of the electrostatic lens and the beam limiting device, and then the theoretical simulation proves that the spectrometer has the expected kinetic energy resolving power. After the device was set up, the delayed ionization process of C60 molecular beam in the nanosecond laser field was studied, and a two-dimensional time slice image was obtained in which the C_ (60) ~ + ions were gradually narrowed as the delay time increased. The analysis shows that the Coulombic coupling between C_ (60) + ions generated by laser pulses will extend the lateral distribution of the two-dimensional slice images and extract the influence of Coulomb coupling on the initial translational energy of C_ (60) ~ + ions. And by analyzing the quantitative dependence of the Coulomb coupling between C_ (60) ~ + ions gradually weakened with the increase of delay time, it is confirmed that this spectrometer has the designed high kinetic energy resolution ability. This work will provide a technical reference for the next step on the detailed study of molecular thermodynamics based on ion-velocity imaging.