Theoretical Study On The Mechanism Of Organic Compounds Enhancing Atmospheric Nucleation And The Development Of Photoelectron Spectroscopy

Atmospheric aerosol particles are formed by gaseous precursors in the atmosphere,which seriously affect human health,climate and air quality.The highly oxidized multifunctional organic compounds and sulfuric acid are important nucleation participants,and some studies have shown that the highly oxidized multifunctional organic compounds could stabilize the sulfuric acid clusters and enhance atmospheric nucleation.However,the interaction of the highly oxidized multifunctional organic compounds with atmospheric pollutants(such as sulfuric acid and methanesulfonic acid)is currently unclear.Therefore,the nucleation mechanism of the isoprene oxidation products 2-methylglyceric acid with sulfuric acid were studied,simultaneously the nucleation mechanism of 2-methylglyceric acid with methanesulfonic acid were also studied as a comparison.The molecular formulas of 2-methylglyceric acid,sulfuric acid and methanesulfonic acid are C4H8O4,H2SO4 and CH3SO3H,respectively.We found that the(C4H8O4)(H2SO4)m(w = 1-2)and(C4H8O4)(CH3SO3H)n(n=1-2)clusters own some partial covalent strong hydrogen bonds and favorable formation Gibbs free energies,binding energies and enthalpies.For both C4H8O4-H2SO4 and C4H8O4-CH3SO3H systems,the conformational populations of different isomers show weak temperature dependence,and the global minima of these clusters are dominant.Our theoretical works indicate that the(MGA)(SA)and(MGA)(MSA)clusters are the most stable ones in the(MGA)n(SA)n(m= 1-2,n= 1-2)and(MGA)m(MSA)n(m=1-2,n=1-2)clusters,respectively.Both the formation rates of(MGA)(SA)and(MGA)(MSA)clusters are quite large and could have significant contributions to NPF,while the formation rates of clusters with other sizes in the system are quite small.The results imply that C4H8O4 is unlikely to occur homomolecular nucleation in the atmosphere,but the interaction between C4H8O4 and H2SO4 indicates that they can effectively contribute to heteromolecular nucleation mainly in the form of heterodimers.CH3SO3H exhibits similar properties to H2SO4 in the ability to form clusters with C4H8O4,but slightly weaker than H2SO4.Theoretical calculations must be combined with experimental testing to fully reveal the problem.Although traditional mass spectrometers can analyze the mass spectrum of a particle,the mass spectrum does not have full specificity due to the complexity of the atmospheric environment.To this end,we have developed an instrumentation device for ion trap mass spectrometry combined with photoelectron spectroscopy.The instrument utilizes a mass spectrometry-photoelectron spectroscopy combination system to obtain not only mass spectrometry but also photoelectron spectroscopy,thereby providing an effective means of researching the chemical composition and structural information of the particles.The instrument can be divided into two parts:the ion transmission system and the laser system.The interaction between the two systems requires precise design and adjustment of the optical path and strict timing control.