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Lei Zhu, Ph.D.
Lei Zhu, Ph.D.
My research program has been designed to investigate and understand what controls the atmosphere’s energy balance and how chemical reactions impact composition, pollutant and oxidant formation in the earth’s environment. Answers to these questions are highly relevant to understanding atmospheric climate change, as well as controlling air pollution and protecting public health.
My group has carried out a number of research projects to address important issues driving atmospheric radiative balance and chemistry with the support of NSF.
- Demonstrated for the first time the existence of water vapor near-UV absorption in the 290-350 nm region and determined water vapor absorption cross-sections. Provided field evidence for water vapor near-UV absorption and estimated its energy budget. Compared the estimated optical depth spectra of ozone with those of water vapor and found that water vapor near-UV absorption significantly affects ozone retrieval from UV measurements. Our work is expected to change the paradigm in atmospheric measurements from UV remote sensing observations and how atmospheric radiation and climate are modeled.
- Demonstrated the importance of gas phase photolysis of 2-nitrophenol and methyl-substituted 2-nitrophenols as missing OH and missing HONO sources in some polluted atmospheric environments. Illustrated why gas phase photolysis of 2-nitrophenols should be included in atmospheric models to close the gap in budgets of OH and HONO for the polluted atmosphere.
- Discovered a new absorption band for nitrate on solid surfaces and determined for the first time nitrate near-UV surface absorption cross-sections. Provided molecular level understanding as to why nitrate photolysis rates on urban grimes and other surfaces are so much faster than those in the liquid phase.
- Measured wavelength-dependent UV absorption cross-sections of surface-adsorbed HNO3 and surface-adsorbed H2O. Surface absorption cross-sections of HNO3 and H2O are several orders of magnitude larger than those in the gas phase. Investigated nitric acid photolysis in the presence of water vapor. Demonstrated that this process does not directly lead to HONO production.
- Investigated adsorbed water UV absorption from monolayer to multilayer, and to heterogeneous nucleation as well as competitive adsorption of HNO3 and H2O on fused silica. Demonstrated the sensitivity and the feasibility of Brewster angle cavity ring-down spectroscopy in studying molecular adsorption on surfaces.
- Investigated gas phase reaction/wavelength-dependent photolysis of vinoxy radical, alkyl nitrates and a wide variety of carbonyl compounds.