中文摘要：

在阈值光电子-光离子符合质谱中，通过增加离子检测端的电极板，并调整相对电压形成渐增的加速电场，获得了很好的离子速度聚焦效果．通过这种电场，使得具有较大平动能的离子团沿飞行方向逐渐膨胀的同时。在垂直于飞行方向受到电场的束缚，最终在探测器的表面实现速度聚焦，形成缩小的图像（即速度成像的放大倍率N〈1），从而确保谱仪能够同时获得较高的平动能分辨率和质量分辨率．应用这种缩小的速度聚焦电场，我们研究了振动态选择的O2＋（B22∑g-）离子解离动力学，获得了碎片离子O＋在阈值光电子-光离子符合条件下的三维时间切片图像，并通过比较两个解离通道所产生的O’不同的平动能分布，证实了这种离子透镜电场在较宽的离子平动能范围内能够始终保持良好的速度聚焦效果．

英文摘要：

A series of electrodes were used to form a new accelerated electric field for ion focusing optics of a threshold photoelectron-photoion coincidence （TPEPICO） mass spectrometer. Ion groups with higher kinetic energy gradually expanded along the direction of flight while they were restricted along the direction perpendicular to the flight tube. Consequently, contractible velocity imaging was achieved on the surface of the detector for all the ions where a magnification factor （N） of less than 1 was obtained for the images. Therefore, good kinetic energy resolution and mass resolving power were obtained simultaneously. Using this novel focusing lens the dissociation of vibrational state-selected O; ions in the B2∑g-; state was reinvestigated and three-dimentional time-sliced velocity images of the O＋ fragment were recorded. By comparing the kinetic energy released distributions of the O＋ that dissociated from the two dissociation channels, satisfied velocity imaging was obtained for the ions with a wide kinetic energy range.