A kinetic and spectroscopic study of chemistry relating to the atmospheric role of iodine species

The impact of halogen chemistry on important atmospheric processes such as ozone
depletion and (potentially) climate regulation is becoming increasingly apparent. Yet only the
most fundamental atmospheric chemistry of halogen species is included in global tropospheric
models. Spectroscopic measurements of the concentration of halogen species within the Earth's
atmosphere, and the accurate determination of kinetic information regarding the rates and
mechanisms of chemical processes in the laboratory, greatly facilitate the evolution of our
quantitative understanding of the atmospheric role of halogen species, ultimately leading to their
inclusion in atmospheric chemistry models.
The research presented in this thesis addresses previously un-investigated areas (or
areas requiring further elucidation) of iodine chemistry. Specifically, Chapter Three uses new
spectroscopic data to reassess the viability of a laser-induced fluorescence (LIF) instrument for
the detection of ambient iodine monoxide radicals (10), a key species in the atmospheric
chemistry of iodine, which may help to enhance our understanding of important atmospheric
processes via its spatially resolved detection. Chapter Four presents a kinetic and spectroscopic
investigation into the mechanism and products of the reaction of CH21 radicals with 02, which
has potential implications for particle formation in the marine boundary layer (MBL). The
reaction of Cl atoms with alkyl iodides, CH3I and CH212, has been studied in detail by the
detection of adducts formed in these reactions, which have been observed by LIF for the first
time, and is the subject of Chapter Five. As part of the course of this PhD, the reaction kinetics
of the reaction of 10 with dimethyl sulphide (DMS) was investigated. The results obtained have
led to a re-evaluation of the atmospheric significance of this reaction.
The data obtained assist the development of our knowledge of the atmospheric
chem istry of iodine species and, at a more fundamental level, the electronic structure and
physical processes of gas phase species.