Spectroscopic studies of ozone- the Earth's UV filter

Abstract

Ozone depletion remains one of the major social ± political environmental issues of the day. Annual polar ozone depletion has been well documented, particularly in the southern hemisphere; as polar ozone depletion worsens annually, regions of lower latitude are increasingly aOE ected in both the southern and northern hemispheres resulting in growing public awareness and concern. As stratospheric ozone decreases so does the protection it oOE ers from harmful ultraviolet radiation. The grave consequences of unchecked ozone depletion on the Earth' s biological systems has provided the impetus for a global research eOE ort to determine the causes and eOE ects of ozone depletion. To date, major attention has been given to ozone destruction cycles catalysed by the chemical by-products which result from the photolysis of man-made chloro¯uorocarbons (CFCs) and nitrogen oxides. However in order to understand the underlying chemistry and physics of ozone depletion a wide range of laboratory studies and detailed theoretical calculations are also needed to characterize ozone dissociation dynamics and electronic structure. A full characterization of ozone spectroscopy and dissociation dynamics is far from complete. This is in part due to the di culty in preparing such a reactive (and unstable) molecule for the necessary laboratory studies and partly due to the di culty in accurately modelling ozone' s ground state structure. Thus despite its crucial importance, studies of ozone spectroscopy and collision dynamics have only been re® ned within the last decade. In this review, the structure, spectroscopy and dissociation pathways of ozone will be discussed within the context of their role in the stratosphere.

Electron scattering in ozone and chlorine dioxide

“…There has been a considerable amount of recent interest in electron scattering from ozone (Mason and Pathak 1997), reflecting its importance in atmospheric science. Earlier work includes electron energy-loss spectra obtained by Celotta et al (1974), Swanson and Celotta (1975) and Johnstone et al (1992), the electron impact ionization studies of Siegel (1982), Newson et al (1995), and measurements of the vibrationally elastic scattering crosssection by Shyn and Sweeney (1993).…”

Experimental studies on electron scattering from atoms and molecules: the state of the art

“…In the last few years major advances have been made in the study of electron scattering from atmospheric radical species, in particular ozone and the chlorine oxides (OClO and Cl 2 O). A review of electron scattering from ozone has been recently published (Mason & Pathak 1997). The low-energy spacing between the lowest unoccu-Figure 12.…”

Investigation of 3-fragment photodissociation of O3 at 193.4 and 157.6 nm by coincident measurements

“…Radiation within this spectral range would otherwise reach the Earth's surface with detrimental effects to life, causing damage to DNA and other biomolecules. 3 While the photochemistry of ozone has been studied extensively in this spectral region, its photodissociation at higher photon energies is less well-characterized, owing to the lower solar flux, coupled with the high absorption cross-section of molecular oxygen at λ < 200 nm. 4,5 As such, ozone absorption is considered less important at these wavelengths, but ozone does have a weak, unnamed absorption band between 150 and 200 nm.…”

“…Three-fragment dissociation resulting from photoexcitation, charge exchange, or collisions has been observed in other molecules, such as H 3 16, 17 and sym-triazine, 18 directly or deduced from product distributions (see Refs. 19-23 for some examples).…”