Instruments Development Based On Linear Ion Trap Mass Spectrometer And Theoretical Study Of Oxalic Acid In Aerosol Nucleation Mechanism

Atmospheric aerosols have impact on the Earth's climate,solar radiation,cloud and rain formation,atmospheric visibility,and human health.new particle formation is an important source of atmospheric aerosols and cloud condensation nuclei,new particle formation mainly includes two stages of nucleation and growth.The nucleation stage plays a very important role in new particle formation,which determines the rate of new particle formation.At present,the understanding of the new particle formation mechanism is still not comprehensive,mainly due to the limitations of detection technology and the complexity of the atmospheric environment.Therefore,except the theoretical calculations and model simulations,the development of the related experimental instruments to obtain the structures and compositions information of the nucleation clusters is particularly important for studying new particle formation mechanisms from a microscopic perspective.This work was mainly carried out from the theoretical calculation research and the development of experimental instruments,the contents are as follows:1.Based on the Basin-Hopping(BH)algorithm combined with the density functional theory(DFT),the clusters formed by oxalic acid and ammonia and its hydration cluster structures were studied in the first time.Furthermore,the structural stability,thermodynamic properties,electrons density and non-covalent interactions of the clusters,temperature and humidity effects on cluster formation,and optical properties were also discussed.Proton transfer was found to play an important role in cluster stability.The possible concentration of H2C2O4-NH3 clusters in the atmosphere was 8.02×105 molecules cm-3,and monohydrate and dihydrate of(H2C2O4)(NH3)2 are relatively abundant and these clusters may contribute to atmospheric aerosol nucleation.2.An electrospray ionization source-semi-cylindrical linear ion trap tandem mass spectrometer has been designed and built based on a linear ion trap mass analyzer.The experimental instrument has been firstly debugged and quality analysis performance tested,and high resolution and analysis performance have been obtained.Ion trap mass analyzer has many advantages:(1)simple structure and small size;(2)no excessively requirement of the working vacuum,which could reduce the size of the vacuum system;(3)tandem quality analysis capability,multiple quality analyses can be achieved only through an ion trap;(4)storage and accumulation of ions,helping increase sensitivity.The application of the ion trap mass analyzer has important research significance for improving the gas phase ion detection sensitivity and reducing the overall volume of the instrument.3.An infrared photodissociation spectrometer was designed based on a hyperbolic linear ion trap mass spectrometer and a reflectance time-of-flight mass spectrometer.In addition,basing on the debugging results of semi-cylindrical linear ion trap tandem mass spectrometer,the improvement of infrared light dissociation spectrometer design was also introduced.Compared with other ion traps of different structures,the hyperbolic linear ion trap was first applied to the infrared photodissociation spectrometer,which enabled the instrument to have better storage capacity and analysis performance.