Organic aerosols (OA) contribute remarkably to total mass of fine aerosols in the lower troposphere, exerting effects on air pollution, global climate and human health. Therefore, analysis of chemical composition of OA in real-time is vital to understanding the formation and reaction mechanisms of organic aerosols. In this work, vacuum ultraviolet (VUV) photoionization mass spectra of squalane aerosol, a good proxy for long chain hydrocarbons often detected in ambient OA, has been performed with a home-made thermal desorption/tunable VUV photoionization aerosol time-of-flight mass spectrometer based on synchrotron radiation (SR). The dependence of photoionization mass spectra of squalane aerosols upon the vaporization temperature and ionization energy were investigated in detail. The ionization energy (IE) of parent molecule (IEsq = 9.43 eV) and the corresponding appearance energies (AEs) of fragments ions were determined. It is shown that the choice of the appropriate vaporization temperature is helpful for analysis of mass spectra of OA, and the measurement of the photoionization efficiency (PIE) curve is crucial to identifying the molecular chemical components of the fragment ions. The dissociative photoionization of squalane aerosol was further studied theoretically with ab initio calculations at M062X level. The qualitative agreement between experimental and theoretical results on dissociative photoionization channels demonstrated that the mechanism of dissociative photoionization of squalane aerosol can be studied by controlling the vaporization temperature, which is important for chemical composition analysis of OA in atmosphere. The findings in this work indicate the potential application of soft ionization aerosol mass spectrometry based on SR for characterization of atmospheric aerosols, especially OA.

Institute of Analytical Chemistry of the Czech Academy of Sciences Veveři 97 CZ 60200 Brno Czech Republic

Key Laboratory of Environment Optics and Technology Anhui Institute of Optics and Fine Mechanics HFIPS Chinese Academy of Sciences Hefei 230031 Anhui China

Laboratory of Atmospheric Physico Chemistry Anhui Institute of Optics and Fine Mechanics HFIPS Chinese Academy of Sciences Hefei 230031 Anhui China

Laboratory of Atmospheric Physico Chemistry Anhui Institute of Optics and Fine Mechanics HFIPS Chinese Academy of Sciences Hefei 230031 Anhui China; Fujian Provincial Key Laboratory of Modern Analytical Science and Separation Technology College of Chemistry and Chemical Engineering and Environment Minnan Normal University Zhangzhou 363000 China; Ningxia Key Laboratory of Green Catalytic Materials and Technology College of Chemistry and Chemical Engineering Ningxia Normal University Guyuan 756099 China

Laboratory of Atmospheric Physico Chemistry Anhui Institute of Optics and Fine Mechanics HFIPS Chinese Academy of Sciences Hefei 230031 Anhui China; School of Environmental Science and Optoelectronic Technology University of Science and Technology of China Hefei 230026 Anhui China

National Synchrotron Radiation Laboratory University of Science and Technology of China Hefei 230029 China

School of Pharmacy Anhui Medical University Hefei 230026 Anhui China

Citace poskytuje Crossref.org