Dielectric Barrier Discharge Ion Source And Distribution Of Water Cluster Molecules In The Atmospheric Environment

Dielectric Barrier Discharge(DBD) is a type of gas discharge under ambient condition.This paper gives an introduction to a new type of ionization source based on dielectric barrier discharge,the plasma of gas(Ar) was generated by dielectric barrier discharge,and the ions of the analyte was generated by the charge transfer reaction with the plasma,the sample was analyzed and detected by the mass spectrum.In this paper,we use rising air bubbles method to generate the mixture of the Argon and the saturated vapor of Carbon tetrachloride,the mixture undergo discharge and then was detected by mass spectrum.The spectrum of Carbon tetrachloride(spectrum of CCl₃⁺) proved dielectric barrier discharge can be used as a new type of ionization source.To study the structure and constitution of the water cluster is a longstanding hotspot.The distribution of water clusters under ambient condition was first tested using a triple-quadrupole mass spectrometer coupled with a dielectric barrier discharge ionization source in this paper.The water exists as clusters rather than a single molecule under the ambient conditions,and the cluster distribution is dependent on the humility of atmosphere,or the water vapor pressure.In addition to the cluster with the magic number n=21,H⁺(H₂O)_n was also observed in the ambient condition,and H⁺(H₂O)₄,H⁺(H₂O)₁₀,and H⁺(H₂O)₁₅ were found more stable according to the experiment.The distribution was related neither to the ion source type,nor the mass filter type.Additionally,the distribution results at different temperature(303K,308K,311K and 313K) were given,to study the heat disassembly phenomenon of the water clusters under ambient condition,means that the big size water clusters will decompose to small size with the rising of the environment temperature.The dissociation products of H⁺(H₂O)_n(n=4-16) clusters were further studied with a collision induced dissociation(CID) method.The results showed that with the size accretion of the parent ions,the size of the most stable daughter ions were also largen.The CID products of H⁺(H₂O)₁₀ with the collision gas pressure were also studied.There was no selectivity for the CID process of water clusters,and the selective dissociate channel did not exist.Furthermore,simulation work of H⁺(H₂O)₄ was also done to identify the most stable structure of the ions.