Dissociation Of N₂ And NH₃ Molecules Induced By Highly Charged Ion Impact

Dissociation of molecules induced by different projectiles,e.g.photons and charged particles has attracted more and more attention in recent years.In the present thesis,based on experiments done using the combination of an electron cyclotron resonance ion source positioned on a 150 kV platform and a cold target recoil ion momentum spectrometer at Fudan University,we have investigated the dissociative double ionization of two important nitrogen-containing molecules,i.e.nitrogen and ammonia,following the impact by highly charged ions?HCIs?of 3 keV/u Ar⁸⁺.Through analyzing the kinetic energy releases?KERs?and momentum correlation of the fragments from different dissociation channels,information concerning the fragmentation dynamics,i.e.electronic states and fragmentation mechanism of corresponding molecular dications was obtained.The present thesis composes of two main parts.First,the KER was measured for the benchmark channel of Coulomb exploded N₂,e.g.N₂²⁺?N⁺+N⁺.The results of this are agreement with reported data and also provides a calibration for the ion momentum measurement.Second,in order to identify the fragmentation mechanism of ammonia dications,the experiments of ammonia in collision with 3 keV/u Ar⁸⁺ions were performed.Three different types of NH₃ dications are observed,namely long-living,rapidly dissociating and slowly dissociating NH₃²⁺ions.KERs were determined for the two-body fragmentation channel NH₃²⁺?H⁺+NH₂⁺in coincidence with different scattered projectiles of Ar⁷⁺and Ar⁶⁺.The difference between these two KER distributions is explained from the perspective of double electron capture.For the three-body channel NH₃²⁺?H⁺+NH⁺+H,the 3D momenta of ionic fragments are measured,which is then analyzed through Dalitz plots and Newton diagrams to study the correspondence of the fragmentation mechanism of NH₃²⁺ions to the KER relevant to this channel.