Study On Optical And Mass Spectroscopy In Supersonic Molecular Beam

Supersonic jet expansion is an important technique in molecular spectrum, photolysis, chemical dynamics, and new material preparation. Some techniques combined with supersonic jet expansion have been broadly applied to the physical and chemical and other subjects' investigations.A supersonic molecular beam, pulsed discharge spectroscopic experimental system was developed. Firstly nitrogen was used as a sample to optimize the experimental system. According to the Boltzmann distribution under the local thermal equilibrium, the N₂ vibrational temperature of the upper electronic state in the second positive system (C³Î _u - B³Î _g) was obtained via emission spectral analysis.The study of hydroxyl radical (OH) is of great importance in plasma physics, astrophysics, atmospheric science, combust science, environmental science, chemistry and other related subjects and applications. Meanwhile, OH, one of the simplest polar molecules, is now becoming the great interest in molecular Stark cooling, and thus in the study of cold chemical reaction, for an example its reaction with cooled H2CO. In this thesis, the OH molecular beam was generated by DC pulsed discharging the H₂O seeded in the argon buffer gas. The dependences of the experimental results on the experimental parameters were studied, and a theoretical model which can basically interpret the experimental was proposed. Moreover, by analyzing the intensity distribution of OH emission spectrum of the (0, 0) band in the A²âˆ‘-X²Î  system, the excited state's vibrational and rotational temperatures were determined to be 4170K and 3075K, respectively, in our experimental condition.In addition, the time-of-flight mass spectrum of products of photo-dissociation/ionization of NH₃ seeded in argon was studied by utilizing the 4^th harmonic laser beam of Nd:YAG pulse laser (60mJ, 4ns@266nm) in the thesis. After system being optimized, the fragments' yields were obtained, and the translational temperature was estimated around 10K which will be helpful to our further work on cold molecules. The comparison of electric discharge and photodissociation to generate NH was also discussed.