Abstract Title: Comparison of UV-Vis Measurements and Computational Spectra of Benzo[a]pyrene and its Dione Derivatives to Improve Air Quality Models
Abstract Submitted to: ATMOSPHERIC SCIENCES
Abstract Text:
It is important to characterize all sources of reactive oxidants in the lower troposphere, including singlet molecular oxygen, in order to model air quality effectively. Little is known about the sources and potential roles of singlet molecular oxygen in the lower atmosphere. Preliminary data suggest select polycyclic aromatic hydrocarbons (PAH) and their oxidized derivatives react with ground state oxygen in the presence of sunlight to produce singlet molecular oxygen. The overall goal of this study is to compare measured UV-Vis spectra to calculated spectra for classes of PAH poorly documented in the literature. More specifically, this project compares the measured UV-Vis spectra of benzo[a]pyrene and its dione derivatives to the UV-Vis spectra from the computed vibrationally resolved absorption spectra based on the Franck-Condon principle. These computation methods change from one vibrational energy to another to calculate an absorption/fluorescence spectrum. With the Gaussian 16 software package, we employed a three-step computational approach to compute the UV-Vis spectra. A TD-SCF calculation was performed at the Hartree-Fock level and a 6-31G basis set. Measured spectra were produced using 0.05mM concentration solutions solvated with toluene or chloroform for each of the compounds tested. We determined that the computed and experimental UV-Vis spectra were qualitatively similar. The UV-Vis spectra for benzo[a]pyrene, benzo[a]pyrene-3,6-dione, benzo[a]pyrene-1,6-dione and, benzo[a]pyrene-6,12-dione had a bathochromic shift (red shift) which favored longer wavelengths. However, the dione derivatives experienced more of a hypochromic effect compared to benzo[a]pyrene since there was a decrease in molar absorptivity. These results verify that computed spectra could be used to complement experimental investigation necessary for this class of compounds.
Adrina Alexan
Description
Funded by:
Current Institute of Study/Organization: California State University, Los Angeles
Currently Pursuing: Master's
Country: US