The atmospheric oxidants, such as OH, Cl, NOx, or ozone, react with the relevant atmospheric substrate or transient species, leading to the formation of radicals and stable products, which could potentially have impacts on the environment by creating soot particles or aerosol. The pollutants reportedly have an impact on the human respiratory system as well as on the biotic world 1. So, study of these reactions with suitable and efficient experimental and theoretical methods holds promise for the betterment of atmosphere. O'Keefe and Deacon developed the Cavity Ring Down Spectroscopy (CRDS) to measure a very week forbidden transition of O2 excited state. The method is based on measuring the rate of absorption rather than the magnitude of a light pulse's absorption owing to mirror loss in a Febry-Perot cavity configuration made of two highly reflecting mirrors. Aromatic hydrocarbons like benzene, toluene, and xylene are oxidized to form the resonance stabilized radicals in the atmosphere. Among, all the isomers of xylene, o-xylene is one of the most widely used isomer, which finds its usage in paints, adhesives and coating etc. When o-xylene gets emitted into the atmosphere, it reacts with atmospheric oxidants and forms the resonance stabilized o-xylyl radical. O-xylyl radicals contribute significantly to the formation of poly aromatic hydrocarbons (PAHs) and can undergo self-reaction or decompose to produce substituted aromatic compounds or radicals, including the substituted Fulvenallene radical. The study involving the measurement of the absolute absorption cross-section of o-xylyl radical in the wavelength range of 468-469 nm using CRDS will be discussed.
The reduction of the ozone depletion layer in the stratosphere is effectively facilitated by the emission of halogen compounds (X=F, Cl, Br, and I) from anthropogenic and artificial resources, mostly in coastal areas (2,3). The oxide substituent of these compounds mainly monoxides (XO) have major role in the ozone depletion. Peroxy radicals, RO2 (R=H, CH3, C2H5, C3H7 etc.) are the primary consumers of halogen monoxides in the atmosphere. The reactions involving the highly abundant CH3O2 among alkyl peroxy radical with the various halogen monoxides are critically important and will be discussed in detail
References:
1) Matsugi, A., Miyoshi, A., Chem. Phys. Lett., 2012, 521, 26-30.
2) Enami, S., Yamanaka, T. et al J. Phys. Chem. A, 2006, 110, 9861–66.
3) Shallcross, D.E., Leather, K.E., et al, J. Phys. Chem. A, 2015, 119, 4618-32.