Threshold photoelectron-photoion coincidence (TPEPICO) is a powerful method to prepare and analyze internal energy- or state-selected ions. Here, we review the state-of-the-art TPEPICO imaging technique combining with tunable vacuum ultraviolet (VUV) synchrotron radiation and its recent applications at Hefei Light Source (HLS), especially on the fundamental data measurement and the dissociation dynamics of ions. By applying the double velocity map imaging for both electrons and ions in coincidence, the collection efficiency of the charged particles, the electron energy resolution and the resolving power of the released kinetic energy in dissociation have been greatly improved. The kinetic energy and the angular distributions of fragment ions dissociated from parent ions with definitive internal energy or state have been acquired directly from TPEPICO images. Some dissociation mechanisms involving non-adiabatic quantum effects, like conical intersection and internal conversion, have been revealed. Moreover, the mass-selected threshold photoelectron spectroscopy (MS-TPES) shows tremendous advantages in isomer-specific analysis of complex systems.
Xiang-kun WuXiao-feng TangXiao-guo ZhouShi-lin Liu
