A cold target recoil-ion momentum spectroscopy for the investigation on the dynamics of atomic and molecular reactions in Shanghai

A cold target recoil-ion momentum spectroscopy to study the fragmentation of molecules impact by electrons has been described, which mainly comprises a pulsed electron gun, a supersonic gas jet, a time-of-flight (TOF) spectrometer, a multi-hit position sensitive detector and a data acquisition system. According to the measured TOF data and corresponding positions information on the detector, the recoil-ions’ trajectories can be reconstructed and their initial 3D momentum vectors can be calculated. The energy spread of the electron gun, about 8.5 eV, and the resolution of momentum component parallel and perpendicular to the TOF direction for recoil-ions, about 0.23 and 0.35 a.u., respectively, are obtained by using helium as the gas target. To test the performance of the setup, the fragmentation of nitrogen induced by 100 eV electrons impact is investigated and some reaction channels with different kinetic energy distributions, like dissociative ionization and Coulomb explosion, are analyzed. Good agreement is achieved with previous studies.